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Academic research paper on topic "PREPARATION AND PERFORMANCE STUDIES ON POLYETHERSULFONE ULTRAFILTRATION MEMBRANES MODIFIED WITH GELATIN FOR TREATMENT OF TANNERY AND DISTILLERY WASTEWATER"

World Congress on Conservation Agriculture

4-7 February 2009, New Delhi, India

Innovations for Improving Efficiency, Equity and Environment

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Published by 4th World Congress on Conservation Agriculture and printed at M/s Print Process, 225, DSIDC Complex, Okhla Industrial Area, Phase I, New Delhi 110 020

Contents

Plenary Session

Enhancing Resource Productivity and Efficiency through Conservation Agriculture

Thomas A. Lumpkin and Ken Sayre...................................................................................................................3

Conservation Agriculture: Why?

Paul L.G. Vlek and Lulseged Tamene...............................................................................................................10

Indigenous Knowledge in Conservation Agriculture

Y.L. Nene.............................................................................................................................................................21

Will Improving the Productivity of "Green" Water Lead to Food Security?

Colin J. Chartres.................................................................................................................................................24

Global Conventions and Partnerships: Their Relevance to Conservation Agriculture

R . S. Paroda.........................................................................................................................................................30

Impact Analysis of Conservation Agriculture

S . S . Johl..............................................................................................................................................................35

Theme 1: Resource Productivity and Efficiency Session 1.1: Soil and Residue Management

No-Till System Applied to Northern Africa Rain-Fed Agriculture: Case of Morocco

Oussama EL GHARRAS, Azeddine EL BRAHLI and Mohamed EL MOURID...............................................41

Critical Research for Dryland Conservation Agriculture in the Yellow River Basin, China: Recent Results

Yan Changrong, He Wenqing, Mei Xurong, John Dixon, Liu Qin, Liu Shuang2, Liu Enke..............................51

Innovations through Conservation Agriculture: Progress and Prospects of Participatory Approach in the Indo-Gangetic Plains

M.L. Jat, Ravi G. Singh, Y.S. Saharawat, M.K. Gathala, V Kumar, H.S. Sidhu, and Raj Gupta..................60

Strategies to Overcome the Competition for Crop Residues in Southern Africa: Some Light at the End of the Tunnel

Patrick C. Wall....................................................................................................................................................65

The Importance of Crop Residue Management in Maintaining Soil Quality in Zero Tillage Systems; A Comparison between Long-term Trials in Rainfed and Irrigated Wheat Systems

Nele Verhulst, Bram Govaerts, Els Verachtert, Fabian Kienle, Agustin Limon-Ortega,

Jozef Deckers, Dirk Raes, Ken D. Sayre.........................................................................................................71

Conservation Agriculture - Constraints, Issues and Opportunities in Rainfed Areas

B. Venkateswarlu, K.L. Sharma and J.V.N.S. Prasad.....................................................................................80

Session 1.2: Input Management (Water, Nutrients, Seed and Agro-chemicals)

Perspectives on Nutrient Management in Conservation Agriculture

Amir Kassam and Theodor Friedrich.................................................................................................................85

Opportunities and Challenges for Water and Nutrient Management in Conservation Agriculture Farming Systems of Asia and Africa

Christian H Roth, Merv Probert, Jack McHugh and Greg Hamilton................................................................93

Polymicrobial Formulations for Enhanced Productivity of a Broad Spectrum of Crops

C.A. Reddy and J.Lalithakumari........................................................................................................................94

Developing Alternate Tillage and Crop Establishment Strategies for Higher Resource Use Efficiencies in the Rice-Wheat System

J.K. Ladha.........................................................................................................................................................102

Session 1.3: Diversified Farming Systems

Lessons Learned from the Extension of Direct Seeding, Mulch-Based Cropping Systems (DMC) in the Main Agro Ecological Zones of Madagascar

Rakotondramanana, O. Husson and A. Rakotondralambo...........................................................................103

Direct Drilling is Behind Agronomy of Opportunity in Tunisia

Moncef Ben-Hammouda, Khelifa M'Hedhbi, Hatem Cheikh M'hame D and Houcine Ghouili......................110

Alternative Land Uses and Farm Diversification Strategies to Strengthen CA

Ademir Calegari.................................................................................................................................................117

A Model Suiting Small Farm Diversification : A Case Study from India

Gurbachan Singh..............................................................................................................................................122

Session 1.4: Irrigated Systems

Rational and Application of CA for Irrigated Production in Southern Europe and North Africa

Helena Gomez-Macpherson, Hakim Boulal, Rachid Mrabet, Emilio Gonzalez.............................................129

Implementing Conservation Agriculture Concepts for Irrigated Wheat Based Systems in Northwest Mexico: A Dynamic Process Towards Sustainable Production

Bram Govaerts, Nele Verhulst, Ken D. Sayre, Fabian Kienle, Dagoberto Flores

and Agustin Limon-Ortega................................................................................................................................136

Rationale for Conservation Agriculture under Irrigated Production in Central Asia: Lessons Learned J.P.A. Lamers, A. Akramhanov, O. Egamberdiev, A. Mossadegh-Manschadi, M. Tursunov, C. Martius, R. Gupta, K. Sayre■ R. Eshchanov and S. Kienzler....................................................................146

Session 1.5: Mechanization and Energy Management

Energy Balance in Conservation Agriculture and Conventional Farming: a Comparison

S.K. Tandon and Surendra Singh.....................................................................................................................156

Actual Challenges : Developing a Low Cost No-till Wheat Seeding Technologies for Heavy Residues; The Happy Seeder

H.S. Sidhu,Yadvinder Singh, Manpreet Singh, J. Blackwell, Harmanjit Singh,

Rajinder Pal Singh and H.S. Dhaliwal and Ajaib Singh...................................................................................167

Actual Challenges: Developing Low Cost No-Till Seeding Technologies for Heavy Residues; Small-Scale No-Till Seeders for Two Wheel Tractors

Israil Hossain; R. Jeff Esdaile, Richard Bell; Chris Holland4; Enamul Haque,

Ken Sayre and M Alam.....................................................................................................................................171

Research and Development of Light No-till Seeders in China

Li Hongwen, Wang Qingjie, Wang Xiaoyan, He Jin, Gao Huanwen, Li Wenying..........................................178

Avoiding Soil Compaction in CA: Controlled Traffic Systems for Mechanized CA and their Effect on Green House Gas Balances

J.N. Tullberg and CTF Solutions......................................................................................................................185

Improving No-Till Seeding Quality with Low Disturbance Furrow Openers and Residue Handling Devices

Augusto Guilherme de Araujo..........................................................................................................................191

Resource Saving Equipment for Conservation Agriculture Leading to Higher Productivity and Profitability

Nawab Ali..........................................................................................................................................................192

Constraints to Zero Tillage in Mediterranean Environments

E . Acevedo, E . Martinez and P. Silva...............................................................................................................195

Breeding for improved adaptation to conservation agriculture improves crop yields

Richard Trethowan,Yann Manes2 and Tariq Chattha......................................................................................207

Adapting Wheats to Zero Tillage in Maize-Wheat-Soybean Rotation System

Man Mohan Kohli and Jorge Fraschina...........................................................................................................212

Challenges and Prospects to Realize Diversified Agriculture in the Tropics: The Brazilian Savannah Case

Carlos R . Spehar...............................................................................................................................................223

Strategies for Developing Rice-Wheat Genotypes for Conservation Agriculture

B. Mishra and Ravish Chatrath........................................................................................................................234

Session 1.7: Indigenous Knowledge and Practices

Blending Indigenous and Scientific Knowledge for Innovative CA Development using Participatory Action Research

H. J. Smith.........................................................................................................................................................242

Adoption of Conservation Agriculture in Kazakhstan

M . Karabayev and M . Suleimenov....................................................................................................................243

Uncertified Organic Farming - Holistic Paradigm Imperative for Mass-scale Sustainable Agriculture

Bharat Mansata.................................................................................................................................................249

Theme 2: Institutional Innovations and Policies

Session 2.2: Integrated Approach for Technology Development and Dissemination

Adoption of Conservation Agriculture Technologies: Constraints and Opportunities

Theodor Friedrich and Amir Kassam...............................................................................................................257

Institutional Innovations for Participatory Approaches for Conservation Agriculture in Africa

Pascal G. Kaumbutho.......................................................................................................................................265

Development, Integration and Dissemination of Resource Conservation Options through Community Watershed Approach

Suhas P. Wani, T.K. Sreedevi, P.K. Joshi and B. Venkateswarlu................................................................277

Fast-tracking Low-Disturbance No-Tillage for Emerging Market Agricultures

C. John Baker and Volodymyr Khorishko.......................................................................................................294

Session 2.3: Capacity Building

Capacity Building: Harnessing Off-farm Employment Avenues in Harmony with On-farm Resources

J. C. Katyal.........................................................................................................................................................306

Human Resource Development for Converting Input (resource) Intensive Agriculture into Input (resource) Efficient Agriculture

Mushtaq Ahmad Gill and Naveed A Awan.......................................................................................................307

Session 2.4: Enabling Policies

Policies and Institutions to Promote the Development and Commercial Manufacture of Conservation Agriculture Equipment

Brian G Sims, Peter Hobbs and Raj Gupta....................................................................................................308

The Tragedy Is On, The Tragedy Is Over: Pastoral Challenges and Opportunities for Conservation Agriculture

Michele Nori and Constance Neely..................................................................................................................329

Theme 3: Environment

Session 3.1: Climate Change

Conservation Agriculture Protocols for Greenhouse Gas Offsets in a Working Carbon Market

Tom Goddard, Karen Haugen-Kozyra and Andy Ridge................................................................................... 341

Carbon Sequestration Opportunities with Smallholder Communities: Forestry, Agriculture and Agro-Forestry

Louis V. Verchot and Viendra P. Singh...........................................................................................................351

Mitigating Climate Change and Better Ensuring Agriculture's Adaptation for Impending Climate Change through Conservation Agriculture

Des McGarry.....................................................................................................................................................362

Greenhouse Gas Mitigation in Rice-Wheat System with Resource Conserving Technologies

H. Pathak..........................................................................................................................................................373

Session 3.2: Biodiversity

Diversifying Crop Rotations with N2-fixing Legumes

Bruno J.R. Alves, Claudia P. Jantalia, Luis Henrique De B. Soares, Segundo Urquiaga

and Robert M. Boddey......................................................................................................................................378

The Importance of Biodiversity in Crop Rotations under Direct Drill in Controlling Weeds, Plant Diseases and Crop Pests

Renato Serena Fontaneli, Henrique Pereira Dos Santos, Leandro Vargas, Joao L. Nunes Maciel,

José Roberto Salvadori....................................................................................................................................389

Enhanced Opportunities for Use of Plant Genetic Resources in Conservation Agriculture Initiatives: A Critical Appraisal

P.L. Gautam, S.K. Sharma and I.S. Bisht......................................................................................................396

Session 3.3: Environmental Services

Environmental Service Provided by Conservation Agriculture in Tropical Rural Catchments: Water and Soil Credits?!"

J. Miguel Reichert, Jean Paolo Minela, Gustavo Henrique Merten2, Nadia Bernardi Bonumâ,

and Dalvan José Reinert...................................................................................................................................407

Role of Carbon in Ecosystem Services from Conservation Agriculture

D . C. Reicosky...................................................................................................................................................418

Weathering the Storms - Conservation Agriculture in Africa's Potential to Ameliorate 21st Century Environments

R . M . Fowler........................................................................................................................................................425

Theme 4: Imapct Assessment and Equity Issues

Session 4.1: Impact of Conservation Agriculture

Global Overview of Conservation Agriculture Adoption

Rolf Derpsch and Theodor Friedrich................................................................................................................429

Adoption and Impact of Conservation Agriculture-based Resource Conserving Technologies in South Asia

Olaf Erenstein...................................................................................................................................................439

Session 4.2: Equity Issues (Employment, Drudgery and Regional Disparities, etc.)

Conservation Agriculture for Drudgery Alleviation in SSA

Josef Kienzle, Amélie Berger, Brian Sims and Tom Apina............................................................................445

Contribution of Commons to Conservation Agriculture in Mountain Areas

Narpat S. Jodha................................................................................................................................................455

Governance and Institutional change in Traditional Commons: Lessons from Chhattisgarh, India

Dinesh K. Marothia...........................................................................................................................................463

Community Management of Common Property Resources in the Agrarian Economy

V.N. Sharda and Swarn Lata Arya....................................................................................................................478

Irrigation Tanks: A New Way Forward? (focus on tanks in South India)

K. Palanisami....................................................................................................................................................492

Improving Efficiency and Sustainability of India's Agriculture through Judicious Management of Common Property Resources : A Perspective

Katar Singh........................................................................................................................................................508

Plenary Session

Enhancing Resource Productivity and Efficiency through

Conservation Agriculture

Thomas A. Lumpkin and Ken Sayre

Director General and Agronomist, International Maize and Wheat Improvement Center (CIMMYT), Apartado Postal 6-641. Mexico DF, Mexico CP 06600 (Email: t.lumpkin@cgiar.org and k.sayre@cgiar.org)

Farmers, agricultural research directors/policymakers, agriculture-based non-government organizations (NGOs), international agricultural research centers (lARCs), and the private agro-business sector, whether in developing or developed countries, are struggling to cope with trade globalization, unstable commodity market prices, unreliable supplies and increasing costs of inputs, concerns about the effects of climate change on future agricultural productivity, and shrinking budgets for many national agricultural research and extension systems (NARES) and lARCs. Yet these sectors are expected to continue to feed and now, in many cases, fuel, a continually growing world population—a population that presents an accelerating demand for agricultural products and entertains the optimistic presumption that farmers will meet this demand using economically viable, ecologically sustainable means. This is a tall order, and for these remarkable outcomes to occur, new crop management technologies that drastically increase the productivity and efficiency of resource use will be required. This does not mean we can forget the population monster: the growth in world population must be slowed even as food production is increased. Rapidly evolving strategies and crop management technologies, such as conservation agriculture (CA), are being developed and used by farmers to confront the issues outlined above, creating innovative and sustainable opportunities for farmers.

Conservation Agriculture: Toward Sustainable, Resource-Conserving Crop Management Systems

In recent years, farmers interested in sustainable crop production systems have begun to adopt and adapt improved crop management practices, a step toward CA, which may be considered the ultimate solution. CA, which focuses on the complete agricultural system, involves major changes in farm cropping operations from the widely used, traditional tillage-based farming practices. Appropriate CA technologies encompass innovative crop production systems that combine the following basic tenets (Sayre 1998; Derpsch 1999):

• Dramatic reductions in tillage

Ultimate Goal - Zero till or controlled till seeding for all crops in a cropping system if feasible.

• Rational retention of adequate levels of crop residues on the soil surface

Ultimate Goal - Surface retention of sufficient crop residues to protect the soil from water run-off and erosion; improve water infiltration and reduce evaporation to improve water productivity; increase soil organic matter and biological activity; and enhance long-term sustainability.

• Use of sensible crop rotations

Ultimate Goal - Employ economically viable, diversified crop rotations to help moderate possible weed, disease, and pest problems; enhance soil biodiversity; take advantage of biological nitrogen fixation and soil enhancing properties of different crops; reduce labor peaks; and provide farmers with new risk management opportunities.

• Farmer conviction of the potential for near-term improved economic benefits and livelihoods from sustainable CA systems

Ultimate goal - Secure farm level economic viability and stability. To achieve this will involve the development of innovation systems focused on the needs of farmers and will include multiple agents who will use their comparative advantages to adapt the principles of CA to the farmers' various biophysical and socioeconomic conditions.

These basic tenets define an approach to crop and soil management that is not location-specific; i.e., the knowledge, the approach, and the fundamental and strategic principles are applicable to a wide range of crop production systems, from low-yielding, dry rainfed conditions to high-yielding irrigated conditions. However, the optimum

application of these techniques will vary across different agro-climatic situations. Specific and compatible management components (weed control tactics, nutrient management strategies, appropriately-scaled implements, etc.) will need to be developed through adaptive research with active farmer involvement to facilitate farmer adoption of CA under contrasting agro-climatic conditions and production systems, much as specific crop cultivar traits (grain color, end-use quality characteristics, genetic disease resistance requirements, etc) vary for specific production situations.

Successful farmer adoption of the first three CA tenets will essentially alter generations of traditional farming practices and implement use (including hand hoes), especially for small- and medium-scale farmers in developing countries who may have had minimal exposure to new farming technologies. In fact, the change in mind-set not only by farmers but also by scientists, extension agents, private sector members, and policy makers in developing as well as developed countries may be the most difficult aspect associated with the development, transfer, and farmer adoption of appropriate CA-based technologies.

In many cases, it may be difficult to explain the importance of CA adoption to farmers beyond its potential to reduce production costs, mainly by tillage reductions. It is therefore necessary to educate farmers on the links between excessive tillage and residue removal with soil sustainability problems, and how these problems can be alleviated through CA. Most smallholder farmers are risk-averse and cannot afford reductions in farm productivity to try a new system. This makes it very important to show immediate benefits in increased productivity of land or labor from CA, apart from the effects of CA on soil and land regeneration. Increased, immediate profits will be relevant to more farmers than the delayed gratification of improving their land gradually through adoption of CA-based technologies. However, if the development, adaptation, and adoption of CA-based technologies are done properly, they can offer farmers and society both possibilities.

Potential CA Contributions to Enhanced Resource Productivity and Efficiency

For CA to succeed, farmers will need to be in the forefront, helping to identify, develop, and deploy new technologies. If we are to insure that adequate food, fiber, and fuel are produced, farmers must employ appropriate crop management technologies not only to stabilize or increase crop production in a cost-effective manner, but also to conserve the integrity and sustainability of their resource base. To achieve this, farmers, researchers, and policy makers alike must insure that the following actions are properly implemented.

1. Increase the efficiency of water use for crop production: Under rainfed conditions this may be done by reducing runoff and evaporative losses, as well as reducing other limitations to crop productivity, to generate "more crop per rainfall drop." Figure 1 below illustrates how the use of sound CA-based technologies (zero till seeded maize in rotation with wheat with surface retention of all crops residues) provided consistently superior rainfed maize yields over 10 years, as compared to the normal, tillage-based, farmer practice for maize production in the central highlands of Mexico. Maize is the predominate crop in these largely rainfed highlands, which average around 500 mm of rainfall annually-1 with a range of 300 - 800 mm-1 which is erratically distributed—50 mm in an hour during an afternoon may easily be followed by two weeks without rain.

Com parison of Rainfed Maize Yield for Different Tillage, Rotation and Residue

Management Practices over 10 Years in Central Mexico (PersonaI Comm. Kenneth Savre - CIMMYT)

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

♦ Maize-Wheat; Zero Till Seeding; All Res ¡dues Retained —■— Continuous Maize, Conv. Till Seeding; All Residues Removed (Farmer Practice) - -•- - Maize-W heat; Zero Till Seeding; All Residues Rem oved

Figure 1

Figure 1 also illustrates how the use of zero till seeding but with removal of all crop residues can lead to serious problems, since the retained residues are crucial to keep rain water in the field. Farmer adoption of reduced/zero till

Table 1. Comparison of estimated irrigation water use for raised bed seeding with furrow irrigation versus flat seeding with flood irrigation for different crops at the Directorate of Wheat Research (DWR), Karnal, Haryana, India.

Crops Irrigation water use (cm) % saving of irrigation water by furrowirrigation

Raised bed seeding with furrow irrigation Conventional seeding on the flat with flood irrigation

Wheat 28 33 17

Maize 25 30 16

Pigeon pea 13 15 16

Soybean 17 20 16

Green gram 17 21 16

Vegetable pea 8 10 18

Mustard 9 11 17

Personal Comm. - Dr. S. C. Tripathi, Agronomist at DWR/Karnal.

seeding without retention of adequate crop residues on the soil surface has led to many failures of these seeding systems, especially for rainfed crop production systems.

Improving the productivity of irrigation water is increasingly important: in many developing countries, especially in Asia, irrigated crop production accounts for a major portion of strategic food supplies, insuring food security. The water resources available for irrigation are becoming increasingly scarce and irrigated systems are becoming more fragile, especially with respect to increases in soil salinity from poor irrigation management. Table 1 below illustrates how the use of a CA-based, raised bed, furrow irrigated seeding system in northwest India resulted in both higher yields and significant irrigation water savings for a wide spectrum of crops, when compared to the traditional farmer practice of seeding on the flat with flood irrigation.

The results in Table 1 contribute to the growing evidence that the use of furrow irrigation with raised bed seeding systems can provide striking increases in irrigation water use efficiency, especially permanent raised bed seeding systems where no tillage is used on top of the beds, but beds are "reshaped" as needed in the furrows. As a consequence, in the southern part of the state of Sonora in northwest Mexico, over the past 25 years nearly all farmers have shifted from flood irrigation to furrow irrigation for all crops, and they indicate that they obtain an average irrigation water savings of 20-25% with equal or higher crop yields (Sayre and Moreno Ramos 1997).

2. Halt and reverse the widespread degradation of the soil resource base: Soil degradation from wind and water erosion, as well as a decline in soil physical, biological, and chemical properties, can be linked to excessive levels of tillage and extensive removal/burning of crop residues that are associated with many conventional farming systems.

Figure 2 illustrates the effects of 11 years of tillage and residue management practices on soil wet aggregate stability, one of the more relevant soil physical properties. The conventional tillage treatment with incorporation of all crop residues had a mean weight diameter of aggregates (a measure of aggregate stability) of only 65% of that for the permanent beds with all residues retained. However, the effect of residue retention on aggregate stability is also evident within the permanent bed system: the more residues that are left, the better the aggregate stability. The treatment with permanent beds in which all residues have been burned had a lower aggregate stability than the conventionally tilled practice.

3. Augment crop and soil biodiversity: Augmenting cropping diversity through CA offers farmers alternative, economically viable crop rotation options that help minimize ever-present economic risks and enables farmers to react to rapid fluctuations in markets. In addition, there is considerable evidence that sound crop rotations can result in positive yield increases for the different crops in a rotation. Figure 3 below presents the results for wheat seeded on raised beds with furrow irrigation in northwest Mexico and using different crop rotations. Wheat yields are higher in systems that involve more diverse rotations, as compared to the wheat-fallow system, especially when a legume (in this case chickpeas) is included in the rotation.

4. Confront increasing input prices by boosting input use efficiency to reduce production costs: The increases in the prices of chemical fertilizers, as well as other inputs like herbicides, pesticides, and fuel in the last 18-24 months, have been astounding, especially in many developing countries. In some countries, farmers have access

Figure 2

Figure 3

to only restricted amounts of fertilizers through government rationing programs or have not been able to afford/ acquire fertilizer. There is some concern that CA-based technologies using markedly reduced/zero till seeding systems combined with soil surface residue retention may lead to decreased fertilizer N-use efficiency, requiring the use of higher fertilizer rates to obtain similar yields as conventional till systems. When this has occurred, it has likely been due to factors associated with differing production situations. Obviously, suitable fertilizer management practices that are compatible with appropriate CA-based technologies may result in enhanced N-use efficiency. Figure 4 below illustrates how N fertilizer use efficiency for wheat was enhanced in a permanent raised bed furrow irrigated wheat-maize system in northwest Mexico when adequate residues were retained, as compared to the traditional conventional till system. The results show how the removal of residues on the permanent beds dramatically restricted N use efficiency.

5. Reduce agricultural-related greenhouse gas (GHG) emissions: Soil erosion and leaching of applied agricultural products (fertilizers and pesticides) has long been recognized as detrimental to the environment. However, greenhouse gas (GHG) emissions from agriculture, almost certainly linked to climate change, are a more recent concern and certainly more controversial.

Emissions of CO2 by agriculture can be decreased by reducing tillage and maintaining crop residues on the soil surface to increase C sequestration in the soil (Reicosky 2001), especially when combined with the reduced burning of fossil fuels for field operations associated with reduced/zero till seeding systems. In addition, the field burning of crop residues—yet a widespread practice in developing countries—should be stopped.

Figure 4

Figure 5

At the same time NOx emissions, far more damaging to the environment than CO2, can be reduced by improving N fertilizer management and cutting methane emissions (also more damaging than CO2) by limiting the extent of flooded rice cultivation where appropriate (Patino-Zuniga et al 2009).

If adequate levels of crop residues are retained on the soil surface and combined with reduced or zero till seeding systems, there is good evidence that C sequestration in the soil will occur with corresponding reductions in CO2 emissions (Reicosky 2001). Figure 10 above illustrates the changes in the soil organic content under rainfed maize production in the central highlands of Mexico with contrasting management practices. Zero till with full residue retention has resulted in a substantially higher soil organic matter content (SOM) (and therefore C content) as compared to conventional till with full residue removal, in this experiment established in 1991. This figure also illustrates that achieving a new equilibrium in soil properties through the adoption of CA is a long-term process.

6. Confront the growing shortages of agricultural labor: Agricultural labor shortages are growing even in the two most populous Asian countries—China and India—and this is causing many farmers to consider the adoption of CA-based technologies which, under most situations, can reduce labor requirements. One of the major benefits that smallholder farmers perceive with CA is the labor savings (Wall 2007). In Asia, for example, hand transplanting of puddled rice after conventionally tilled, irrigated wheat has a high labor requirement that peaks in June and July (especially in northwest India). This creates serious labor shortages during this critical time, and has provoked farmer interest in technologies available for direct seeding rice without puddling. One of these technologies is direct (zero till) seeding of rice into dry soil after zero till wheat. Farmer interest is particularly keen in the lowland rice growing areas, where a major portion of the water used in rice production is provided by irrigation.

Experience has shown that dramatic labor reductions are possible with dry soil direct seeding and that substantial irrigation water savings are also possible under many situations. Achieving satisfactory weed control, however, is a challenge that is being resolved with different weed management practices. What is earnestly needed to advance dry soil direct seeded and zero tilled rice is serious efforts by rice breeders to breed and select new, appropriate rice cultivars for this system in the pertinent soil types. There are many positive experiences with direct seeding of rice into dry soil using the available cultivars that were developed under and for transplanted conditions. Certainly, even better results will be achieved with cultivars selected and developed under this management system.

Although there are few reliable economic comparisons of dry seeded, zero till rice compared to transplanted, puddled rice, much more is know in relation to wheat. Figure 6 presents a very thorough on-farm, economic comparison of conventionally tilled irrigated wheat and zero till wheat in the rice-wheat system. Variable costs are substantially lower for zero till (partly due to reduced labor costs) and gross benefits are higher, generating correspondingly higher net benefits for the zero till wheat. These results are similar to most other examples where farmers have adapted suitable CA-based technologies.

Figure 6

7. Reductions in fuel and machinery use: Along with reductions in labor, in mechanized systems CA results in a marked reduction in the use of tractors and equipment, all of which cuts fuel use, reducing both farmers' costs and GHG emissions. Generally, CA reduces tractor use by approximately 70%, depending on the intensity of tillage in the conventional system (e.g. Wall 2002). The reduction in tractor use means that a single tractor can provide the required traction for a greater area. In the example of Bolivia (Wall 2002), this provided for the expansion of the agricultural area using existing tractors, but in the Indo-Gangetic Plains (especially in northwest India) it has

meant that relatively large-scale farmers could become service providers to the smaller farmers in the community. Anyone who has watched a tractor working dry soil, especially alluvial soil, cannot help but notice the cloud of dust in which the tractor and the operator have to work. In CA systems, where residue covers the soil and is not tilled, dust is almost completely absent, benefitting the operator and the farmer, since tractors and equipment operating in dust-free environments require considerably less maintenance and their useful life is extended, reducing again the costs of production.

Toward the Future

Farmer, researcher, and private sector attempts to develop reduced/zero till seeding practices with crop residue retention on the soil surface combined with expansion of crop rotation opportunities have been going on for more than 40 years. This led to the delineation about 25 years ago of the principles or tenets that now characterize CA. It was estimated in 2005 that CA-based technologies using zero till seeding were being practiced on over 95 million hectares worldwide (Derpsch 2005) and currently this area is likely to be approaching 120 million hectares. It is sobering, however, to realize that over 90% of the current area under CA-based technologies occurs in just 5 countries (Argentina, Australia, Brazil, Canada, and the USA) and that less than 5% involves crop production systems under gravity-based irrigation systems. This poses two questions: why has there been such meager adoption of these technologies under irrigated crop production situations, and what factors are constraining farmer adoption of CA-based technologies in other countries?

The answer to the first question is perhaps less complicated. First, rainfed crop production systems predominate in the five leading CA countries listed above. This has led to the dedication of more time, funds, and effort by farmers and researchers to improve crop management practices for rainfed situations. Second, the negative effects of excess tillage and crop residue removal and/or burning are much more obvious under these rainfed conditions: extensive wind and water erosion, crop failures in drought years, etc. As a correlate, the effects of excessive tillage and residue removal on soil health and quality are not as apparent under irrigated conditions, as their effects may be masked by irrigation and additional fertilizer use.

The answer to the second question (what factors seem to be constraining farmer adoption of CA-based technologies in other countries?) is more difficult to explain. Two things that characterized the rapid and extensive adoption of CA-based technologies in the five countries, especially Brazil and Argentina, were, firstly, that farmers realized they had a problem they needed to overcome, and secondly, farmers organized themselves and together began to develop many of the new CA-based technologies. In fact in both of these countries, most agricultural researchers and policy makers initially (and in some cases for several years after) flatly stated that CA would not work. It is also important that most farmers in CA-adopted countries are large-scale mechanized farmers who are able to experiment and bear more risk than small-scale farmers. Large farmers also normally have better links to information systems and are therefore in a better position to circumvent bottlenecks in knowledge flow.

These three key ingredients appear to be important if the development of CA-based technologies is to occur. In most other countries, for various reasons, this development and adoption has not happened or is only just beginning. For example in the higher latitudes, because of the slower breakdown of organic matter and often less intense rainfall, the impact of tillage on soil quality is not as marked as in tropical and subtropical environments. In the latter regions, smallholder farmers poorly linked to information systems, resource poor, and risk averse predominate. They require considerably more support to be able to understand the problems behind their declining yields and increasing costs.

Meanwhile, CA efforts in most countries are outside the mainstream efforts of the NARES. When only a few individuals are convinced of CA's benefits, it can result in a confrontational situation with the mainstream "regular agronomists, soil scientists, etc." who still believe that a good tilth is a prerequisite to successful crop production. The fact that many research and extension directors, as well as university professors, are in this latter category means that it is exceptionally difficult for a few individuals to bring about change in institutional thinking.

Given the widespread soil degradation occurring in the developing world, it is entirely relevant that the three principles of CA (dramatic tillage reductions/zero till, rational crop residue management, and diversified crop rotation, all acting together to economically benefit farmers) should guide routine agronomic and cropping systems activities. They should provide the foundation upon which the development of new practices is based, rather than as a parallel option to mainstream research activities that continue to focus on improving the current tillage-based production

systems. Further degradation of the resource base dedicated to agriculture due to continued, widespread use of tillage-based production systems is obviously unsustainable and therefore neither a valid nor ethical option for agricultural research and development. Continuing to rely on efforts to fine tune the conventional tillage-based crop production systems where crop rotations are generally absent and crop residues are removed, grazed, and/or burned will, at best, limit us to small production increases, and, in all likelihood, result in further land degradation and the demise of agriculture.

Therefore, CA must be brought into the mainstream of crop management research and be closely linked with crop breeders and other agricultural disciplines to insure the development of tactical management practices (cultivars, weed, pest, disease, water management strategies and practices, etc.) suitable for CA-based crop management technologies. CA must not continue to be sidelined as an alternative development pathway, as it represents our best option for a sustainable future.

References

Derpsch, R. 1999. Expansión mundial de la SD y avances tecnológicos. In Proceedings of the 7th National Congress of AAPRESID, 18-20 August 1999. Mar del Plata, Argentina.

Derpsch, R. 2005. The extent of Conservation Agriculture adoption worldwide: Implications and impact. III World Congress on Conservation Agriculture: "Linking Production, Livelihoods and Conservation," 3rd to 7th October 2005, Nairobi, Kenya. 15 p.

Patino-Zuniga, L., J.A. Ceja-Navarro, B. Govaerts, M. Luna-Guido, K. D. Sayre and L. Dendooven. 2009. The effect of different tillage and residue management practices on soil characteristics, inorganic N dynamics and emissions of N20, CO2 and CH4 in the central highlands of Mexico: a laboratory study. Plant Soil. 314: 231-241.

Reicosky, D.C. 2001. Effects on soil organic carbon dynamics: Field experiments in the U. S. corn belt. In D. E. Scott, R. H. Mohtur and G. C. Steingerdt (eds). Sustaining the Global Farm: Selected papers from the 10th International Soil Conservation Organization Meeting held May 24-29, 1999 at Purdue University and the USDA-ARS National Soil Erosion Laboratory. pp 418-485.

Sayre, K.D., Moreno Ramos, O. H. 1997. Applications of raised-bed planting systems to wheat. Wheat Special Report No. 31. Mexico, D. F.: CIMMYT.

Sayre, K.D. 1998. Ensuring the use of sustainable crop management strategies by small wheat farmers in the 21st century. Wheat Special Report No. 48. Mexico, D.F. CIMMYT.

Wall, PC. 2002. Extending the Use of Zero Tillage Agriculture: The Case of Bolivia. Paper presented at the International Workshop on Conservation Agriculture for Sustainable Wheat Production in Rotation with Cotton in Limited Water Resource Areas, Tashkent, Uzbekistan, October 13-18, 2002.

Wall P.C. 2007. Tailoring Conservation Agriculture to the needs of small farmers in developing countries: An analysis of issues. Journal of Crop Improvement 19, 137-155.

Conservation Agriculture: Why?

Paul L.G. Vlek and Lulseged Tamene

Center for Development Research (ZEF), University of Bonn, Walter Flex Str. 3, 53113

This paper first assesses the processes and rates of land degradation (mainly soil erosion, nutrient depletion and soil carbon loss) in the world of conventional agriculture based on studies conducted in different places of the world. The paper goes on to evaluate the benefits of conservation agriculture in retarding land degradation by reviewing some research results worldwide. Evidence collated from different sources show that population pressure and unsustainable uses of land are causing severe land degradation and food insecurity in many places of the developing world. This is likely to increase with growing population pressure unless measures are in place to be able to produce more food from less land through more efficient use of natural resources and with minimal impact on the environment. Conservation agriculture, which is mainly based on three principles - minimum soil disturbance, permanent soil cover, and appropriate crop rotation, has become an interesting intervention since it is economically profitable, environmentally safe, and practically efficient as demonstrated on over 95 million ha of land worldwide where it is adopted. If implemented properly, conservation agriculture is a suitable approach to fulfill the Millennium Development Goal 1 ("... eradicate extreme poverty and hunger ...") and Goal 7 ("... ensure environmental sustainability ..."). The wide acceptance by many countries also shows that farmers are convinced of the benefits of the technology.

1. Land Degradation: Challenges to Estimation

Land degradation is a serious environmental problem that threatens ecosystem health and food security worldwide. This environmental problem has been a major global issue during the 20th century and will remain high on the international agenda in the 21st century (Eswaran et al., 2001). Though methods to assess land degradation on a large scale are deficient, there is growing concern that degradation of agricultural soil resources is already seriously limiting production and diminishing ecosystem services (Vlek, 2008).

There is ample literature about the magnitude of land degradation. Most focusses on specific geographic regions and generally provides gross estimations which may not be adequate to target conservation practices. Thus, information related to degradation patterns that show spatial differences are important. The absence of studies that indicate the spatial distribution of land degradation at global or continental scales causes problem when attempting to answer questions such as "where should one invest research and/or management efforts in order to target high problem areas?" This is particularly critical in developing regions where such resources are limited. Methods are needed to identify hot-spot areas where land degradation.

A better understanding of the extent and nature of land degradation remains imperative, but spatially distributed quantitative data on land degradation is scarce (Vlek et al., 2008). The Global Assessment of Soil Degradation -GLASOD (Oldeman et al., 1990) is one of the oldest attempts to assess the severity of land degradation worldwide. The GLASOD is based on expert surveys that gave a snapshot impression of the situation in the late 1980ies but failed to capture the dynamics of the process. In addition, the study has become outdated. More recently, some global/ regional land degradation assessments using remote sensing technologies have been published (e.g., Prince, 2004; Herrmann et al., 2005; Wessels et al., 2007), mostly focused on the dynamics of degradation processes in arid and semi-arid areas. Three major recent works by Vlek et al. (2008), Bai et al. (2008) and Hellden & Tottrup (2008) outlined elaborated analysis of land degradation at the sub-continental and global scales based on long-term satellite and rainfall data. These studies tried to infer land degradation from the long-term relationship between vegetation productivity and weather dynamics. Table 1 summarizes the spatial distribution of land degradation compiled based on the three studies.

From table 1, it is possible to see differences in the three studies. It is very likely that those who categorized land degradation for GLASOD into different levels would have different perceptions and opinions, which may lead to under or over estimation of processes. In the case of Bai et al. (2008), the proportion of areas experiencing land degradation is calculated by considering all pixels showing a declining trend irrespective of significance level (Bai et al., 2008). The inclusion of pixels that do not experience significant long-term decline may cause over estimation of degradation zones, provided that other assumptions are valid.

Table 1. Land degradation extents by sub-regions

Sub-region GLASOD (UNEP, 1992) LADA (Bai et al., 2008) Vlek et al. (2008) Vlek et al. (In press)

Sub-Saharan Africa 10 26 10 30

Asia and the Pacific 6 21 - -

North Africa & Near East 7 3 - -

Europe 12 11 - -

North America 0 20.3 - -

South America 5 23 - -

Note that Vlek et al. (2008) is based on pixels experiencing significant decline in vegetation productivity but without correcting for atmospheric fertilization effect while Vlek et al. (In press) is based on significant declining pixels but after correcting for atmospheric fertilization effect.

Vlek et al. (2008) analyzed the spatial patterns of land degradation in sub-Saharan Africa (SSA) and indicated that about 10% of SSA experiences land degradation while over 45% shows improvement in land productivity. Many other studies that analyzed the long-term trend of vegetation productivity in the Sahel belt also showed a widespread improvement in vegetation productivity beginning from the early 1980s (Eklundh & Olsson, 2003; Herrmann et al., 2005; Hickler et al., 2005). These studies also highlighted that the observed improvement in long-term trend in vegetation productivity could not totally be explained by improvement in rainfall after the frequent droughts of the 1980s. This means that other processes are in play for the observed "wide-area" biomass greening. The suggestion by Olsson et al. (2005) and Herrmann et al. (2005) that the greening of vegetation has exceeded what can be explained linearly by a recovery in the rains since the early 1980s in certain locations also supports the possible existence of another driver. As the observed greening in general is 'extensive' it may also not be possible to ascribe it fully to improved and successful land management, though such practices have played central role in some regions of West Africa (Reij et al., 2005).

One major hypothesis for the observed improvement in land productivity (vegetation greenness) revealed in recent regional and global studies is the potential impact of atmospheric fertilization (Vlek et al., 2008; Hellden and Tottrup, 2008). In fact, there are many studies that highlight the benefits of CO2 -or NOx- fertilization to enhance plant growth and development (e.g., Lewis et al., 2004; Ainsworth & Long, 2005; Long et al., 2006; Reay et al., 2008). In an attempt to disentangle the impact of atmospheric fertilization on long-term improvement in biomass and thus its possible masking effect of actual land degradation, Vlek et al. (in press) re-calculated the extent of land degradation after "calibrating" the potential impact of atmospheric fertilization using pristine lands with minimum population density and no cultivation/grazing practices. The basis of the hypothesis is that a positive fertilization effect might result in "greeninc(' of vegetation as viewed from space and thus could mask real degradation due to processes such as land conversion, selective logging, overgrazing and nutrient mining (Fig. 1).

Figure 1. Processes showing the potential effect of atmospheric fertilization in masking land degradation. Note that if rainfall and human management cannot adequately explain the observed greening in biomass, the most plausible factor could be atmospheric fertilization. If atmospheric fertilization enhances photosynthesis and thus biomass greening as observed from space using satellite sensors, it might have concealed possible land degradation caused by selective logging, land conversion, over-grazing (Vlek in press).

Based on the above hypothesis, Vlek et al. (In press), re-calculated land degradation and found the situation to be much more serious, with 30% of SSA experiencing degradation processes instead of the 10% without considering the potential impact of atmospheric fertilization. This means that the real degradation extent has been masked due to atmospheric fertilization which could confuse policy design and conservation planning in the region. However, the results of this analysis need to be tested based on high resolution data and field observation.

The above analysis generally shows that quantifying land degradation and understanding the processes in play at global/regional scale is not an easy task. However, the problem is serious (see below) and could endanger the environment and the sustainability of agriculture for future generations. There is therefore a need for a coordinated effort to try to map land degradation and analyze the key processes or drivers that underlie the problem as a guide to sound decision making.

2. The Threat of Land Degradation: How Costly It Is?

Since thousands of years, increasing human needs often changed the natural system from one that is stable and virtually closed to one that is degrading and more or less open (Vlek, 2008). Several efforts have been made to study the rates and processes of land degradation at different scales in various locations of the world. All studies show that land degradation is a real problem affecting livelihoods and the environment. On a global scale the annual loss of 75 billion tons of soil translates into US$400 billion per year, about US$70 per person per year (Pimentel et al., 1995; Lal, 1998; Eswaran et al., 2001). A recent study (Den Biggelaar et al. 2003) shows that the value of annual production losses for some selected crops worldwide could amount to over US $400 million. Yield reductions in Africa due to past soil erosion may range from 2 to 40%, and if the present trend of erosion continues unabated, yield reductions may average 16% by 2020 (Dregne 1990; Lal, 1995). In South Asia, annual loss in productivity due to water and wind erosion is estimated at 36 million tons of cereal equivalent valued at US$7200 million (UNEP, 1994). The above figures and many other sources show that the damage inflicted on soils due to land degradation over many years are significant and have resulted in valuable land becoming unproductive and often eventually being abandoned (Pimentel et al., 1995; Pimentel and Kounang, 1998). The increasing demand for food due to population growth requires increasing production which often leads to exploitation of marginal areas and competition with other land uses. Generally, the economic impact of land degradation is severe in densely populated regions of South Asia and sub-Saharan Africa. Unfortunately, many of these regions are facing complex economic problems that prevent them from escaping the trap of land degradation caused poverty because of their limited resources. Then, once land degradation sets in it is likely to result in a vicious feedback loop and a land degradation-productivity decline-land degradation nexus.

3. Major Land Degradation Processes

Due to the escalating human population and the requirement of ever-increasing food supplies, soil erosion, water scarcity, and loss of biodiversity have gained recognition as prime environmental problems throughout the world. The main land degradation processes such as erosion, nutrient mining, carbon loss, etc. are caused or amplified by human activities, mainly agriculture. These processes are likely to become more severe as population grows and the demand for more land and food increases.

Soil Erosion

Soil erosion due to water and wind is one of the most serious forms of land degradation but its true extent is difficult to assess. Yet, soils today are being degraded at a much faster rate than they can be formed by natural processes (Martius et al., 2001). Tillage, often excessive, as practiced in conventional agriculture is one of the most important drivers of erosion (Elliott, 1986; Kay, 1990; Reichert and Norton, 1994; Papendick and Parr, 1997; Salonius, 2008). Although soil erosion takes place very slowly in natural ecosystems and its cumulative impact on soil quality over billions of years has been significant (Pimentel et al., 2005); this is of no consequence on a human time scale.

About 50% of the earth's land surface devoted to agriculture is more susceptible to erosion because of removal of vegetation before planting and frequent cultivation of the soils. As a result, soil erosion on agricultural land is estimated to be 75 times greater than erosion in natural forest areas, and about 75 billion tons of fertile soil is lost from world agricultural systems each year (Myers, 1993). Worldwide, erosion on cropland averages about 30 t/ha-yr, with a range of 0.5 to 400 t/ha-yr (Pimentel et al., 1995). Based on a compilation of worldwide data, Lal (1994) showed that the yield of rainfed agriculture may decrease by ca. 29 percent over the next 25 years because of erosion. El-Swaify (1994)

indicated that water erosion accounted for about 55 percent of the almost two billion ha of degraded soils in the world. Soil erosion losses are highest in the agro-ecosystems of Asia, Africa, and South America, averaging 30-40 t/ha-yr of soil loss (Taddese, 2001). Due to erosion during the last 40 years, about 30% of the world's arable land has become unproductive and much of that has been abandoned for agricultural use (Kendall and Pimentel, 1994).

Soil Nutrient Mining

Soil nutrient mining occurs when extraction of useful nutrients from the soil by agriculture exceeds the rate of replenishment in the system. Nutrient depletion in soils adversely affects soil quality and reduces crop yield and consequently poses a potential threat to global food security and agricultural sustainability. Continued nutrient mining of soils would mean a future of ever increased poverty, food insecurity, environmental damage, and social and political instability (Henao and Baanante, 2006). The degradation of soil in general and nutrient mining in particular is typically a 'creeping environmental problem' which hinders the initiation of counterbalancing measures (Glantz, 1998; Martius et al., 2001).

As the world population keeps growing, balanced ecosystems are on the decrease and nutrient ledgers all over the world have become increasingly negative (Smaling et al., 1997). In almost all countries of the world, food production is currently dependent on depleting large quantities of nutrients from soil reserves and this is likely to continue. Globally, soil nutrient deficits were estimated to accrue at an average rate (kg ha"1 yr"1) of 19 N, 5 P, and 39 K in the year 2000, respectively (Tan et al., 2005). A study by Sheldrick et al. (2002) estimated the world average soil nutrient depletion to be 12 kg N ha"1, 4.5 kg P ha"1, and 20 kg K ha"1 for the year 1996.

Nutrient mining and its negative consequences in Africa are the highest in the world (Vlek, 1993; Henao and Baanante, 2006). Based on nutrient balance studies and field observations across Africa, soil-fertility depletion in smallholder farms is the fundamental biophysical root cause of declining per capita food production in the region (Pieri, 1989; Stoorvogel & Smaling, 1990; Van der Pol, 1992; Smaling, 1993; Sanchez et al., 1997). Studies show that an average of 660 kg N ha-1, 75 kg P ha-1, and 450 kg K ha-1 has been lost during the last 30 yr from about 200 million ha of cultivated land in 37 African countries (Stoorvogel & Smaling, 1990; Smaling 1993; Sanchez et al., 1997, Smaling et al., 1997). During the 2002%2004 cropping season, about 85% of African farmland (185 million hectares) had annual nutrient mining rates of more than 30 kg/ha, and 40% had annual rates greater than 60 kg/ha (Henao and Baanante, 2006). About 95 million hectares of soil have reached such a state of degradation that only huge investments could make them productive again (Vlek, 1990; Henao and Baanante, 2006). The main causes of fertility decline were depletion due to crop-harvest removals (residues), leaching and soil erosion, lack of supplemental nutrients and mineral fertilizers, unbalanced fertilization, and cultivation of low-potential areas (Smaling, 1993; Sanders et al., 1996; Shepherd & Soule, 1998). These studies depict the urgency of a sustainable nutrient management plan for Africa and many other places in the world to circumvent the potential impact of nutrient deficit on food security and environmental quality.

Soil Carbon Loss

Soil carbon/organic matter is usually referred to as 'black gold' because of its vital role in physical, chemical and biological processes within the soil system (Reicosky and Saxton, 2007). Soil erosion results in the removal of organic matter and essential plant nutrients from the soil and the reduction of the soil depth. These changes not only inhibit vegetative growth, but reduce the presence of valuable biota and the overall biodiversity in the soil (Pimentel et al., 1995).

Conversion of virgin land for cultivation and grazing, repeated cultivation promoting soil respiration without additional carbon inputs and soil erosion are the main causes of loss of organic matter. The estimated total loss of carbon through soil degradation since the advent of agriculture about 10 000 years ago represents 16-20% of the present-day global soil carbon stocks of 1200-1500 Gt (Rozanov et al., 1990; Haider, 1999). Intensification of agriculture based on conventional techniques has amplified and accelerated the age-old problem of soil degradation causing a C loss of 30 - 50% over the past century during which many soils were brought into cultivation (Schlesinger, 1986; Hillel, 1991).

Since the mechanization of agriculture began a few hundred years ago, scientists estimate that some 78 billion metric tons of carbon once trapped in the soil have been lost to the atmosphere in the form of CO2 (Lal, 2004). Murty et al. (2002) showed that conversion of forest to agricultural land led to an average loss of about 22% of soil C. The mineralization rate of SOC may range from about 20% in 20 years in temperate climate to about 50% in 10 years in the

tropics (Woomer et al., 1994). Several researchers observed an exponential decline in soil organic matter content with cultivation time in soils of West Africa (Brams, 1971; Jenkins and Ayanaba, 1977; Lal, 1979).

4. The Role of Conservation Agriculture in Sustaining Land Productivity

The above evidence suggests that unsustainable exploitation of land resources is leading to widespread degradation of resources serious implications for food security and ecological integrity. The situation is not likely to improve in light of the increasing world population along with its increased demand for higher quantities and quality of food and water, a challenge being imposed on future generations. The world community is well aware of this challenge since the publication of the Millennium Ecosystem Assessment (2005).

Untill the middle of last century, the increase in food production in most countries was achieved by bringing new land into agricultural production. However, reserves of potentially arable prime agricultural land are dwindling (Bockman et al. 1990; Crosson and Anderson 1992) and the remaining land is claimed for numerous purposes, including the provision of essential ecosystem services. There are also indications that the highly effective fertilizer and seed technologies introduced over the past four decades may be reaching a point of diminishing returns (Cassman et al. 1995; Flinn and De Datta 1984). Furthermore, new technologies such as genetically engineered, yield-increasing plants are not expected to be major factors in food production increases in developing countries over the next few decades (Hazell 1995; Peng et al. 1994). Consequently, keeping pace with population growth while dealing with increasing land scarcity and degradation will be more difficult than in the recent past.

The millennium development goals 1 and 7 of reducing poverty while ensuring environmental health would point towards systems that conserve resources and maximize efficiencies of resource use. With soil organic matter a key resource to conserve, the agricultural research community has re-assessed the costs and benefits of conservative soil management systems. Food security, ecological integrity and environmental health may be achieved by reducing tillage, leaving residues on the field augmenting nutrient inputs and reducing pest pressures through crop rotation, in short through conservation agriculture (FAO, 2008).

Conservation agriculture, that involves an application of modern agricultural technologies to improve production, enables maximization of yields but also helps maintain ecosystem health and integrity unlike the traditional systems which mainly intend to maximize yields sometimes at the expensive of the environment (Dumanski et al, 2006). Expansion of conservation agriculture can create a win-win situation through promoting more efficient crop production and reducing soil degradation while maintaining ecosystem integrity. As a result, the impacts of conservation agriculture have been markedly positive both in agricultural, environmental, economic and social terms (Garcia-Torres et al., 2003 and Bishop-Sambrook et al., 2004; FAO, 2002; Dumanski et al., 2006).

Because of its significant contributions, the importance of conservation agriculture is growing worldwide where it currently spans over millions of hectares (Riberio et al., 2007). The FAO (2008) estimates its coverage at about 95-98 million hectares, depending on whether zero-tillage, conservation tillage, direct seeding/planting and/or organic farming are all include in the calculations. This worldwide expansion of the technology is clear evidence of its benefits to farmers. Conservation agriculture has wide range of benefits including improvement in soil fertility, reduction in soil erosion, carbon accumulation, savings in time and energy (fuel), and increase in biodiversity (Knowler, 2003; Reicosky and Saxton, 2007; FAO, 2002, 2008).

Conservation Agriculture and its Role in Reducing Soil Erosion

Some studies have indicated that conservation agriculture is an effective way of controlling erosion (e.g., Packer et al., 1992; Uri et al., 1999). Soil erosion in Brazil fell from 3.4-8.0 t/ha under conventional tillage to 0.4 t/ha under no-till, and water loss fell from approximately 990 to 170 t/ha (Sorrenson et al., 1997, 1998). A watershed study in Brazil showed a 22% reduction in sediment load from 1994 to 1998 because of no-till adoption (Derpsch, 2001b). In Paraguay, 23 t/ha/year of soil are lost on average when using conventional agriculture whereas only 0.53 t/ha/year are lost using the no-till system (Venialgo, 1996).

It is important to note that the damage of lost soil in conventional tillage has on- and off-site aspects. It does not only affect farmers situated upslope, but soil is deposited in creeks and rivers also cause sedimentation of rivers, lakes and dams affecting down-slope inhabitants. This deposition of sediments in unwanted places has negative implications on the rural road system, hydraulic energy generation, drinking water production and recreational areas, resulting in significant expenditures for maintenance.

Conservation Agriculture and its Role in Improving Carbon Stock

While conventional cultivation generally results in loss of soil C and nitrogen (Mann, 1986), conservation agriculture has proven potential of converting many soils from sources to sinks of atmospheric C (Kern & Johnson, 1993; Reicosky, 1997), sequestering carbon in soil as organic matter. In general, soil carbon sequestration during the first decade of adoption of best conservation agricultural practices is 1.8 tons CO2 per hectare per year. On 5 billion hectares of agricultural land, this could represent one-third of the current annual global emission of CO2 from the burning of fossil fuels (FAO, 2008). Lal et al. (1998) estimated that widespread adoption of conservation tillage on some 400 million ha of cropland by the year 2020 may lead to total C sequestration of 1500 to 4900 Mg.

Leaving crop residue on the field is another practice which could have an important impact on the global carbon cycle (Lal, 1997). The annual production of crop residue is estimated to be about 3.4 billion Mg in the world (Lal, 1997). If 15% of C contained in the residue can be converted to passive soil organic carbon (SOC) fraction, this may lead to C sequestration at the rate of 0.2 x l015 g/yr (Lal, 1997). Similarly, restoring presently degraded soils, estimated at about 2 billion ha, and increasing SOC content by 0.01%/yr may lead C sequestration at the rate of 3.0 Pg C/yr. Systems, based on high crop residue addition and no-tillage, tend to turn the soil into a net sink of carbon (Greenland and Adams, 1992; Reicosky et al., 1995; Bot et al., 2001). In the USA, the total loss of carbon, from a plot of ploughed-under wheat residues, was up to five times higher than from plots not ploughed, and the loss of carbon was equal to the quantity of carbon in the wheat residues which had remained in the field from the previous crop (CTIC, 1996). Conservation tillage adoption on three-quarter of the land would half this respired CO2 as compared to 1993, representing an accrual of almost 400 million tons (Bot et al., 2001).

Net soil C stock changes for US agricultural soils between 1982 and 1997 due to sifts towards conservation agriculture are estimated to amount to 21.2 MMT C year-1 (Eve et al., 2002). At an average rate of 0.51 t/ha year, Brazil is sequestering about 12 million t of carbon on 23.6 million ha of no-tillage adoption. In Canada, at a C02 sequestration rate of 0.74 t/ha farmers practiing no-till would be sequestering about 9 million tons of C02 from the atmosphere each year, while at the same time enriching the soil in carbon (Bot et al., 2001). It is estimated that wide dissemination of conservation agriculture (which leaves at least 30% of plant residue cover on the surface of the soil after planting) could offset as much as 16% of worldwide fossil fuel emissions (CTIC, 1996).

Estimated Monetary Values of Conservation Agriculture

Conservation agriculture in the form of no-tillage has now been adopted on more than 95 million ha world wide and farmers are showing increasing interest in the technology. Approximately 47% of the no-tillage technology is practiced in South America, 39% is practiced in the United States and Canada, 9% in Australia and about 3.9% in the rest of the world, including Europe, Africa and Asia.

Brazil increased its grain production by 67.2 million tons over 15 years by adopting the no-tillage system. Assuming conservative average prices of US$ 150/t, this means additional revenue of about 10 billion dollars (Derpsch and Benites, 2003; Derpsch, 2005). Similarly,grain production in Argentina increased from 28 million tons in 1988 to 74 million tons in 2001 with adoption of conservation agriculture (Derpsch, 2005). An additional 46 million tons of production at average prices of US$ 150/t, means additional revenue of almost 7 billion dollars, of which a great portion can be attributed to the adoption of the no-tillage technology (Derpsch, 2005).

In Western Australia, it is believed that adoption of no-tillage practices has increased crop production by at least 3 million tons in the year 2000. Likewise production in 2001 was increased by an extra 5 million tons and in 2002 by another 4 million tons (Derpsch and Benites, 2003; Derpsch, 2005). At an average grain value of US$ 150/t, this is US$ 1.8 billion additional revenue. In two regions of Paraguay, Sorrenson (1997) compared the financial profitability of conservation agriculture on 18 medium and large-sized farms with conventional practice over a 10-year period. He found that by the tenth year net farm income had risen on the conservation agriculture farms from under US$10 000 to over US$30 000, while on conventional farms net farm income fell and even turned negative. In the USA, Uri et al. (1999) estimated that the realized erosion benefits (avoided losses from sheet, rill and wind erosion) from the existing areas under conservation tillage ranged from US$90 million to US$289 million in 1996.

A study that assessed the impact of zero tillage in the rice-wheat system of India (Laxmi and Erenstein, 2006) showed that investment in zero-tillage was highly beneficial with a benefit-cost ration of 39, a net present value of US$ 94 million and an internal rate of return 57%. A similar study in the Punjab region of Pakistan (Sawrwa and Goheer,

2007) shows that zero tillage technology is the most economical and attractive option for wheat cultivation. Crop yield using zero tillage (3410 kg/ha) was significantly higher than conventional method (3123 kg/ha) with significantly lower total cost of production (Sarwar and Goheer, 2007).

All these examples and many others available for different regions of the world have demonstrated the significant impact of adopting conservation agriculture including no-tillage technology. The observed gains in crop production and environmental protection are encouraging signs and a compelling argument that conservation agriculture should be practices in other regions as well. Especially developing countries that require improved agricultural production the most could benefit. Awareness creation, policies and incentives could help promote conservation agriculture and its benefits to these regions.

5. Conclusion

Inappropriate agricultural cultivation systems are one of the main reasons for the poverty and food insecurity faced by smallholders in most parts of the rural regions in developing countries. Unsustainable agricultural practices lead to an exhaustion of forest and soil resources, which results in reduced land productivity, land degradation, and a reduction in biodiversity. Conservation agriculture, which is mainly based on the three principles of minimum soil disturbance, permanent soil cover and crop rotation, has shown to improve, conserve and use natural resources in a more efficient way through integrated management of available soil, water and biological resources. It is now widely recognized as a viable concept for sustainable agriculture due to its comprehensive benefits in economic, environmental and social terms . Its ability to increase grain yields to provide better economic performance and reduce production risks and to improve energy use efficiency has been well-documented. What is required is better understanding of its performance and requirements across wider geographic regions and environmental conditions to enable the diffusion of the technology. For its successful implementation in developing regions where it is needed most, the design and dissemination of cost-effective farming tools, access to herbicides and economic incentives will be required in addition to creating awareness.

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Indigenous Knowledge in Conservation Agriculture

Y.L. Nene

Asian Agri-History Foundation, Secunderabad, 500 009, India

Ever since mankind started practicing agriculture, there was a beginning of awareness of resource conservation. We find evidence of conservation practices in all ancient cultures. Since I am familiar more with Indian classic literature on agriculture that has been published by my Foundation (Asian Agri-History Foundation - AAHF) in the last 12 years, my lecture includes most information from literature published by AAHF.

As most of us know, according to Food and Agricultural Organization (FAO) of the United Nations, "Conservation agriculture is a concept for resource-saving agricultural crop production that strives to a achieve acceptable profits together with high and sustained production levels while concurrently conserving the environment." (FAO, 2007). Aspects of conservation that we normally deal are the management of soil, water, crop diversity, animals, storage of produce (seed, fertilizer, etc.), and maintenance of tools, implements, machinery, etc.

The following paragraphs refer to the relevant contents from some ancient texts of India.

1. Rigveda (c. 8000 BC)

This is the oldest text compiled by mankind (Nene and Sadhale, 1997). We can note reference to conservation agriculture in some of the ruchas (verses). Rigveda insists that natural forces (earth - solid matter; water - liquid matter; air - subtle matter; fire - energy; and akasa - the opposite of matter) must remain in harmony with each other and also the mankind must not disturb the balance between them. Following verses relate to conservation agriculture. The verse numbers are quoted at the end of each verse for ease to locate in Rigveda, which is voluminous.

"O cows! Procreate calves, select fine quality grass, and drink clean, safe water from ponds." (6:28:7).

"O humans! Do not kill a cow who is mother of Rudras, daughter of Vasus, sister of Aditya, milk bearing, innocent without complex" (8:90:15).

"O Pusha! Do not destroy the trees that support birds but destroy those who hate me". (6:48:17).

"Let the soil get soaked with water and give us harvests in the years to come". (4:57:7)

"Let our ploughs open the soil happily, let the ploughman walk happily with the bullocks, and let clouds soak the lands with water. Give us happiness. (4:57:7, 8)

Cow protection, cattle management, discouraging cutting trees, desire for sufficient rain, and contented animals and farmers are the conservation issues covered in these verses.

2. Krishi-Parashara (c. 400 BC)

Parashara stressed soil management, seed health, and overall farm management that included water harvest and conservation, animal management, and maintenance of implements (Sadhale, 1999). No commentary is made since the verses are self-explanatory. Some of the key verses are:

"Farms yield gold if properly managed but lead to poverty if neglected".

"Even a fourfold yield of crops procured at the cost of health of the bullocks perishes soon by the sighs of their exhaustion."

"The bullocks of the farmer who keep the cow shed, strong, clean, and free of cow dung grow well even without special nourishment".

"Crops grown without manure will not give yield."

"Any implement which is not sufficiently strong or is not manufactured as per the (above - said) measurements will, at the time of farming operations, obstruct the work at be no doubt about it."

Pa ras ha ra every step. There should

"Uniform seeds produce excellent results. Hence every effort should be made to procure uniform seeds."

"One should (therefore) put in maximum effort to procure and preserve these seeds. The origin of plentiful yield is the seed."

"What hope of harvest can that foolish farmer have who has not made arrangements for preserving water for the crop during Ashwin (October) and Kartika (November)?

3. Kautilya (321-296 BC)

The Varta (crop production, animal husbandry, and trade) was considered one of the sciences of the time. Kautilya mentions intercropping of medicinal plants with any field crop. An example of wasteland utilization was planting cucurbits on river banks, after the excess water receded. The practice continues even today in all parts of India. Some significant statements made by Kautilya are:

"Whoever hurts or causes another to hurt, or steals, or causes another to steel a cow, should be slain."

"The Superintendent of forest produce shall collect timber and other products of forests by employing those who guard forests."

"Brahmins shall be provided with forests for soma plantation, for religious learning, and for performance of penance, such forests being granted with safety for animate and inanimate objects, and being named after the tribal name (gotra) of the Brahmins resident therein".

4. Kashyapiyakrishisukti (800 AD)

Kautilya

Kashyapa

This treatise is a detailed one and gives advice on management of farm not only to farmers but also to kings. There are details about rice growing practices that are widely followed in India today (Ayachit, 2002)

"Land is intended to receive excellence in every age."

"A good quality land yields good results to everyone. Confers good health on the entire family, and causes growth of money, cattle and grain."

"To the west, north, east, or south of the villages and cities at the most convenient places, he (king) should prepare reservoirs of water according to the condition of the land."

"The reservoir of water to be founded should be deep, equipped with barriers, splendid in the shape of a bow, long in some cases, round in others but essentially unfathomable".

"They should also be equipped with inlets for water. Hence they should be founded near

some hill or a high-level ground joined with a lake".

"The king should plan its construction at such places as not to cause fear of danger from flooding. Such reservoirs should be regularly examined."

"Large forests teeming with various trees, on the forest lands, or on the outskirts, or interiors of existing forests, or on mountain slopes should be propagated."

About canals for irrigation, "Even more than the ponds, lakes, wells, etc. protection of canals should be treated by them (farmers and the king) as their dharma" said the sages who know the truth.

"That water (therefore) should be preserved by all (sorts of) efforts, as agriculture is said to depend on water. Hence, kings and (other) eminent persons should obtain water by exerting everywhere in the seasons and conserve it."

For rice, "The second cultivation in a year is fruitful everywhere and is therefore recommended on various types of farmlands. For taking up this second operation, it is essential to raise the fertility of the soil, which can be achieved by using manure of goat-dung, cow dung, and vegetation (green manure)."

5. Vrikshayurveda (c. 1000 AD)

Vrikshayurveda by Surapala is a 'complete' treatise on arbori-horticulture. It also emphasizes the importance of trees and environment. Some of the verses carry deep meaning (Sadhale, 1996).

Importance of growing trees is versed beautifully below by Surapala.

"Ten wells are equal to one pond.

Ten ponds are equal to one lake.

Ten lakes are equal to one son.

Ten sons are equal to one tree."

". . . . one should undertake planting of trees, since trees yield the means of attaining dharma, artha, karma, and moksha (the four aims of life)".

"By planting all kinds of trees, useful for fruits and flowers, a person gets reward of thousand cows adorned with jewels."

Surapala

"Seeds which are treated and preserved (in prescribed manner) are all good for use. Trees grown from such seeds bear for ever abundant flowers and fruits of an excellent quality."

6. Krishi Gita (c. 1500 AD)

Parshurama

Parshurama recommended deep summer ploughing. This has been in practice in Kerala for several centuries.

Green manuring was recommended for rice.

Although forest clearing was recommended as a means to expand cropped areas, farmers were also encouraged

to plant trees and other woody perennials.

References

Ayachit, SM. (Tr.). 2002. Kashyapiyakrishisukti (A Treatise on Agriculture by Kashyapa). Agri-History Bulletin No. 4. Asian Agri-History Foundation, Secunderabad-500009. India. 158 pp.

Food and Agricultural Organization (FAO). 2007. Agriculture and Consumer protection Department, Rome, Italy. Available from http:/ /www.fao.org/ag/ca/ (accessed November 2007).

Nene, YL and Sadhale. Nalini. 1997. Agriculture and Biology in Rigveda. Asian Agri-History 3: 177-190.

Sadhale, Nalini (Tr.) 1996. Surapala's Vrikshayurveda (The Science of Plant Life by Surapala). Agri-History Bulletin No. 1. Asian Agri-History Foundation, Secunderabad-500009. India. 94 pp.

Sadhale, Nalini (Tr.). 1999. Krishi-Parashara (Agriculture by Parashara). Agri-History Bulletin No.2. Asian Agri-History Foundation, Secunderabad-500009. India. 94 pp.

Shamasastry, R. 1961. Kautilya's Arthasastra. Seventh Edition. Mysore Printing and Publishing House, Mysore, India. 488 pp. (First edition published in 1915).

Will Improving the Productivity of "Green" Water Lead to Food Security?

Colin J. Chartres

Director General, International Water Management Institute, PO Box 2075, Colombo, Sri Lanka

Politically, one of the most pressing questions for many countries over the next 50 years will be that of whether they will be food-secure in the face of potential recurring world food crises. During the 2008 food crisis, although global food stocks reached worrying lows, there was still enough food available to feed everyone. The key problems were those of demand, driving prices above the reach of the poor and food stocks being geographically in the wrong place. Logically, for most countries, food security can be achieved by a combination of domestic production and imports, but as was observed in the 2008 food crisis, logic often flies out of the window in the face of adversity. Some food exporting countries adopted policies that were clearly driven by fear and stopped exports. Other countries froze grain prices which was detrimental to poor farmers, encouraged black marketeering and did little to aid the urban poor. So a critical need for many countries are policy settings that encourage domestic production via increasing productivity, recognize the benefits of importing "virtual water" via trade in food, and enable poor farmers to benefit from price rises so that they in turn can invest in more productive systems.

Currently the world population is 6.7 billion and this large number is forecast to increase to about $9 billion by 2050. Given a number of drivers and uncertainties that impinge on food production, the fact that close to 1 billion people are undernourished and the fact that we have already come perilously close to a famine-based disaster last year, there has to be concern as to whether we can feed 9 billion people in the future.

Availability of enough fresh water for rainfed and irrigated cropping is probably going to be the single most important factor in our quest to feed so many more mouths. The Comprehensive Assessment of Water Management in Agriculture (Comprehensive Assessment of Water in Agriculture, 2007) has already indicated that if we proceed with a "business as usual" approach, water scarcity will cause us to fail in this quest. "Business as usual" means maintaining water productivity levels at their current low rates. The Comprehensive Assessment was, however, more optimistic about the future if we can substantially lift water productivity levels via a combination of biophysical and engineering inputs and policy levers. Whilst some informed commentators indicate that we will only be able to produce enough food through expanding irrigation, the fact is that approximately 75% of production comes from rainfed areas. This is paralleled by the statistic that 80% of water evapotranspirated by crops comes from rainfed farming areas and the remaining 20% from irrigation areas (Comprehensive Assessment of Water in Agriculture, 2007). However, the figures for gross value of production indicate that only 55% comes from rainfed areas indicating the importance of irrigation in terms of its higher productivity per unit area.

This paper examines some of the drivers behind water scarcity and examines ways in which water productivity in rainfed farming systems may be increased to tackle the major challenge of increasing food demand.

Blue and Green Water

Water passing through the hydrological cycle can be viewed as "blue" or "green." Blue water is that found in rivers, lakes and groundwater (aquifers). Green water can be defined as that very significant proportion of water that is stored in the soil. There is a complicated interaction between green and blue water which depends on the factors (climate, topography, soil type, vegetation cover) and processes that control runoff to rivers and deep drainage to groundwater. It is the remaining green water that is available for evapotranspiration back to the atmosphere that is the critical water supply for rainfed cropping and pasture production.

Water Scarcity

The availability of water and access to water will be major issues for economic development and for the livelihoods of the poor, given that they often suffer most when resources are scarce.

Water scarcity can be described as being physical or economic in nature (Fig. 1).

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Figure 1. Global Water Scarcity in 2000

Physical water scarcity results from the allocation of virtually all available water supplies leaving nothing for additional use or for the future, or for the environment. It has become a reality for many regions. Much of south and west Asia, China, the Middle East, northern and southern Africa, southern Australia, and south western USA are in this category. Physical water scarcity will put increasing pressure on water planners and managers to develop ways to better manage their existing water resources, to increase the productivity of water, and to develop "new" sources of water, e.g. "reuse" of wastewater. Many countries have already seen water users turn to groundwater often not cognizant of the high degree of connectivity between groundwater and surface water.

There are however, many areas in the developing world, in particular in Sub-Saharan Africa and parts of Southeast Asia, where there are still available water resources, but development and use of these resources has been constrained by lack of capital investment, or appropriate institutions to support the use of that capital. The resulting "economic" water scarcity has major ramifications for the poor and economic development in general, and its solution has the potential to bring global benefits and reduce stresses on other water scarce areas. The issue of insufficient infrastructure development also relates to limited investment in wastewater treatment facilities and the consequent widespread pollution of clean surface water bodies. Whether in areas of physical or economic water scarcity, a critical factor for the future will be the impact of climate change and ongoing and potentially increasing climatic variability on the availability and use of water resources be it for drinking water, hydropower or irrigation. The impact of climate change will vary depending on geography and scale. In some areas, total rainfall and intensity will increase causing flooding, crop damage and erosion. In other areas, total rainfall may decrease, wet seasons become shorter and variability more extreme with greater frequency of droughts. Learning how to store water better and providing supplementary irrigation to make up for erratic rainfall supplies will be the key to overcome these challenges.

Drivers of Water Scarcity

The recent food crisis was driven by a number of factors including increasing demand due to population growth, increasing biofuels production at the expense of food crops, regional impacts of drought on agricultural water availability and changes in economic and trade policy in some countries.

If we look into the future with respect to water availability, not only continuing population growth ,but also other factors including dietary change to more water thirsty foods, urbanization, increasing biofuel development and hydropower production will all lead to further pressure on water resources and the environment.

Population Growth Impacts

With respect to blue water Falkenmark (2008) defines a use to availability ratio (so-called criticality ratio) and "chronic water shortage" (level of water crowding). She indicates that already 1.4 billion people are living in areas where water is over-appropriated and that 1.1 billion of these people live in areas which are also suffering under severe water shortage. She further forecasts that by 2050, depending on the rate of fertility decline, the population in countries with chronic water shortages (above 1000 people per million cubic meters per year) will be 3 to 5.5 billion. To date, it has been the environment that has suffered as use to availability ratios rise. Whilst many ecologists would argue that a 40% ratio is a threshold above which ecosystem health is impacted, there are a growing number of major rivers that hardly reach the sea any more leading to the concept of "closed basins." Included in this number for, example, are the Murray (Australia), Yellow (China), Krishna (India) and Colorado (USA). Population growth therefore represents the biggest single threat to water supplies and food production.

Dietary Change

On average, 1 calorie of food requires 1 litre of evapotranspirated water to grow it. However, as large numbers of people in developing countries, particularly India and China, have grown more affluent, their taste in food has moved from diets dominated by grain and vegetables to consumption of more protein rich foods including dairy products and meat respectively. A diet without meat requires about 2000 liters of water per day to produce compared with 5000 liters per day for a diet high in grain-fed beef (Renault and Wallender, 2000). If we very conservatively use an average daily calorie intake of 2500, then to feed the 2050 world population of 9 billion, we will need to find an additional approximately 2,100 km3 of fresh water. This figure is undoubtedly conservative as it is based on a relatively low protein diet and minimal food wastage post farm gate.

Biofuel Production

The global financial crisis has seen oil prices tumble from US$150 per barrel to US$37-40 over the last 6 months. Whilst this will undoubtedly have an impact on the attractiveness of ethanol production, growing fossil fuel demand over the forthcoming decades will inevitably see demand for biofuels similarly increasing. So called first generation biofuels production derived from corn, beans and sugar, create competition for not only land, but also water. If ultimately this competition takes over 10-15% of agricultural land, the impacts on food production will be very significant. However there are many uncertainties on the future impact of biofuels on food production given current rates of return, concern that their production is no more greenhouse friendly than fossil fuels and the potential advantages of new technologies that will be able to produce biofuels from crop residues and other wastes.

Urbanization, Globalization and Other Factors

In 2008 the world saw a transition to from one in which more people lived in rural environments to one with more people in the cities and towns. Whilst the turnover point has not yet been reached in the developing world, it is likely to be inevitable in due course. Bigger cities with more industry clearly already compete with agriculture for water resources and this competition will increase. Furthermore, cities generally have political power and the wealth to purchase water from other users. Currently, many agricultural developing countries and developed countries/states such as Australia and California utilize 70% or more of their total available water resources in the agricultural sector. Even if growing urban demand only requires a redistribution of 5% of this water, this will have a significant impact on agricultural production on a global basis.

Globalization will also have a range of impacts on food production. These will include demand for luxury goods such as cut flowers creating competition for land and water in regions close to international airports, product sourcing policies of supermarket chains in developing countries and the recent phenomenon of large food importing countries wanting to buy up large tracts of land in developing countries for food production. Competition for water from the hydropower industry also means that water for agriculture is no longer available at the right place at the right time. All these kind of drivers may significantly impact food production in developing countries and have both beneficial and

adverse impacts on their populations. Lastly, the negative impacts of restrictive world trade policies cannot be overlooked as a factor that may, in countries with abundant water and food production potential, limit the development of their production and marketing capabilities and thus their capacity to contribute to world food production as times get tougher.

Increasing pressure to meet the Millennium Development Goals in terms of water supply and sanitation for the poor also compete for both the water resource and scarce financial resources in the water sector.

Finally, ongoing loss of agricultural land due to urbanization and industrial development and land and water degradation often the result of population pressure will both continue to destroy or reduce the productivity of agricultural land.

Climate Change Impacts

While more detailed regional and local studies are needed to improve understanding of just how climate change will impact food production, there are some ominous signs already appearing that give major cause for concern. Firstly, rainfall and runoff records from countries with Mediterranean climates, such as southern Australia and Spain an Morocco are already indicating that declines in rainfall of up to 30% may be expected with climate change. Studies are also indicating that in some environments for each unit decline in rainfall there is up to a threefold decline in runoff. Data from Central Asia, also suggest that in the long term (30-50 years), runoff from mountain snow melt may also reduce by at least 30%. In the some of the subtropics of Africa, rainy seasons are starting later, have more intense rainfall and are of shorter duration. Even in areas where rainfall is predicted to increase, increases in rainfall intensity may lead to more erosion and flooding. To what extent, such climate change and variability induced impacts on water availability may be compensated for by production being enabled in areas previously too cold for grains is uncertain, but an inescapable fact is that many of the world's poor live in the tropical and subtropical countries likely to be deleteriously impacted by climate change.

Solutions

The analysis of the drivers of water availability demonstrates that it will be foolhardy for any water users to overlook water availability issues in the future. Food crises caused by demand/supply perturbations inevitably impact the poor. Most of the world's poor live in South and East Asia and Africa. Many of the countries in the Asian region, but particularly Pakistan, India and China already have water availability concerns. At the global level, currently, about 7130 km3 of water are evapotranspirated (Figure2) by agriculture annually (Comprehensive Assessment of Water in Agriculture, 2007). Estimates suggest that with current levels of productivity this water requirement will increase by 70-90% by

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Figure 2. Water and land requirements to meet food demand in 2050 under different agricultural scenarios

2050 under current levels of water productivity. The vast volumes of freshwater (1500-6000 km3) dependent upon fertility decline and water productivity improvement) needed to increase food production are highly unlikely to come from simply increasing irrigation area. If we look at Asia, large areas are already under irrigation. In South Asia 106 m ha out of 200 m ha are under irrigation (Fig.3).

Figure 3. The proportion of harvested area that is irrigated

Furthermore, in South Asia and parts of China, there has been very significant expansion of groundwater irrigation over the last 30 years, with many major groundwater systems consequently under unsustainable extraction regimes. Consequently, with the exception of some smaller areas in South East Asia (e.g. Cambodia), increasing irrigation area will not be the major pathway to food production increases in this region of the world. Increasing water productivity in existing irrigation systems, is, however, a different matter and has to be one of the solutions required. Africa, presents a different picture and has more scope to increase irrigation with only 6 m ha out of 163 m ha currently irrigated. However, international financing for irrigation development has reduced dramatically over the last 20 years based on a perception that the green revolution has dealt with food production issues once and for all and more recently, on a perception that large surface irrigation schemes have not been very successful (hence the significant increase in privately financed groundwater irrigation schemes).

Whilst, food scarcity may see the financial pendulum swinging back to investment in surface irrigation, increasing the productivity of rainfed agriculture must be considered as a sound strategy by governments. The key questions are how can this be achieved in the face of a number of limiting factors including low soil fertility, poor water management practices and often limited human capacity manifest in poor farming communities? These issues notwithstanding, a number of options are available. According to the Comprehensive Assessment of Water Management in Agriculture, these include:

• Improving productivity through enhanced management of soil moisture and supplemental irrigation where water

storage is feasible;

• Improving soil fertility management, including the reversal of land degradation; and

• Expanding cropped areas.

If these measures are combined with increasing the productivity of irrigated areas, ensuring that agricultural trade within and between countries is not impeded ,reducing food demand by influencing diets and minimizing post-harvest losses including industrial and household waste, they can have a major impact on improving food production.

The Comprehensive Assessment of Water Management in Agriculture modeled a scenario that assumed zero growth in irrigated areas, which showed that rainfed agriculture could meet the increase in food demands projected for 2050. This optimistic scenario had cereal yield increase by 72% and harvested rainfed area increase by only 7%. This scenario would lead to Sub-Saharan Africa, Latin America and most of Asia being largely self sufficient in producing major food crops, with the exception of maize in east Asia. A more pessimistic scenario that included only modest yield improvements saw rainfed area increasing by 53% to meet future food demands. However, this scenario required countries without available land and/or reliable rainfall to significantly increase food imports. Under this scenario world

trade in food would expand from 14% of production today to 22% in 2050. Potentially, there is the land available to increase production even under the pessimistic scenario, but the extent to which it has better than marginal production capability and the extent to which climatic factors including rainfall uncertainty would limit potential production is uncertain.

The next question to ask is whether the modeled changes could realistically be achieved given current climate and other factors? Both optimistic and pessimistic scenarios call for substantial increases in soil water consumption. For the optimistic scenario with little expansion of rainfed area, improved water management, including small amounts of supplementary irrigation, is a prerequisite for yield increases. This will require more evapotranspiration, part of which can be offset by increasing water productivity by improving the harvest index, by reducing losses from soil evaporation, or by increasing transpiration while reducing evaporation.

The optimistic scenario sees rainfed cereal production improve by 72% with a concomitant increase in water productivity of 32% compared with 20% and 10% respectively in the pessimistic scenario. In total, compared with the year 2000, each scenario would use an additional volume of water of 2150 km3 and 3850 km3 respectively. It is highly probable that increase of water consumption of these magnitudes will have major impacts on river flows and groundwater recharge in most areas, so the optimum pathway would be to follow the optimistic scenario.

Obtaining a 35% increase in water productivity in rainfed agriculture is, however a daunting task. It will require major rethinking of the way in which governments and society view agriculture in general. It will require much better knowledge about soil types and soil water and soil structural management to maximize water availability. It will require major investment in capacity building of farmers and other players in the food production chain. It will require governments to pay very significant attention to developing policy settings that promote agricultural productivity increases that build on knowledge and capacity development as opposed to subsidizing particular aspects of agriculture such as fertilizers. It will also be imperative that investment levels for research and development are stepped back up to levels that they were at the time of the green revolution in order to overcome the very significant challenges facing yield and productivity improvements across the agronomic-water interface. Finally, it will require innovative thinking by all concerned to optimize the best productions systems for given environments that also pay attention to maintaining the provision of ecosystem services.

Conclusions

This paper set out to examine the role of green water and rainfed agricultural production in facilitating the major production increases required to feed the world's growing population. The data presented suggests that rainfed agriculture, because of its widespread predominance, will have to significantly increase its productivity if this is to be achieved. However, the increases are potentially attainable in terms of available land and water resources. However, in some closed river basins any increases in green water use will have serious impacts on other sectors of the economy and the environment. In reality, we have to strive for greater green water productivity as well as developing new irrigation schemes (particularly in Africa) and ensuring policy settings are conducive to the trade of virtual water. The sheer numbers of people wanting to be fed by 2050 mean that the challenge for the agricultural community will be immense and this needs to be recognized by governments across the world in terms of their preparedness to invest in agriculture and natural resource management at hitherto unforeseen levels.

References

Comprehensive Assessment of Water Management in Agriculture 2007. Water for Food, Water for Life: A Comprehensive Assessment of Water Management in Agriculture. London: Earthscan and Colombo: International Water Management Institute.

Falkenmark, M. 2008. Peak Water - Entering an Era of Sharpening Water Shortages. Stockhom Water Front. Dec. Issue, 10-11. Published by SIWI (www.siwi.org).

Renault, D. and Wallender, W.W. 2000. Nutritional Water Productivity and Diets. Agricultural Water Management45, 275-96.

Global Conventions and Partnerships: Their Relevance to

Conservation Agriculture

R.S. Paroda

Chairman, Trust for Advancement of Agricultural Sciences (TAAS), IARI Campus Pusa New Delhi, India, Executive Secretary, Asia Pacific Association for Agricultural Research Institutions (APAARI), FAO Regional Office, Bangkok and Ex-Director General, Indian Council of Agricultural Research (ICAR) & Secretary, Department of Agricultural Research & Education (DARE), Government of India, New Delhi

Since time immemorial, mankind has been relying on farming and natural resources to meet the basic needs of life. Unfortunately, the unprecedented increase in human population during past half century, from 3 billion during 1960 to currently 6 billion, is further expected to grow to 8.5 billion by 2025. Therefore, satisfying the increasing demands for food and other commodities, agriculture sector will have major challenge of improving productivity from same or even less land and other natural resources. Estimates suggest that since 1945, about 23% of the 8.7 billion hectares of global agricultural land, permanent pastures and forests have been degraded. Much of the degradation is mainly taking place on agricultural lands- 74% in Central America, 65% in Africa, 45% in South America and 38% in Asia (Pandya-Lorch, 2000). The study by the UN Food and Agriculture Organization (FAO) led project on Land Degradation Assessment in Drylands (LADA) indicated that an estimated 1.5 billion people depend directly on land that is degrading. Another recent study by FAO, United Nations Environment Programme (UNEP) and World Soil Information, indicates that land degradation is worsening rather than improving, with declining trends revealed across some 24 per cent of global land area. According to this study, the main driver of degradation is poor land management. The study also shows improvements towards sustainable land management, with 19 per cent of crop- and grassland and 10 per cent of forests being managed sustainably or showing improved quality and productivity. The overall picture, however, reveals that land degradation requires renewed attention by individuals, communities and governments through innovation programmes and partnerships. Conservation Agriculture (CA) is also an innovative approach that helps in reducing soil erosion, improves water use efficiency as well as soil health, helps in carbon sequestration, minimizes use of energy and above all improves productivity and income of resource poor farmers (Lal, 1997, 2004). Hence, CA has become a global movement towards sustainable agriculture. This paper summarizes a brief history and future plans of Global Initiatives through Conventions, Congresses and Partnerships for forestalling the degradation of natural resources through adoption of Conservation Agriculture (CA) practices for sustainable development, food security and poverty alleviation.

I. Global Conventions

In view the challenges of resource degradation owing to increasing population pressure, the global community came forward to address this concern through a series of Conventions. The first coordinated effort to revert the process can be traced back to the Stockholm UN Conference on the Human Environment held in 1972, wherein 113 nations adhered to "safeguard and enhance the quality of land and environment". The creation of UNEP in 1973, based in Nairobi, Kenya is one of the major outcomes of the Stockholm Conference. Thereafter, UNEP sponsored a conference on desertification (UNCOD) in 1977 at Nairobi, wherein a world plan of action to combat desertification (PACD) was adopted.

The available information at the time showed that productive land is lost at the rate of 600,000 hectares/year, and that productive land area prone to desertification is about 300 million hectares extending over 100 countries. The cost of productivity lost per year is around US$ 25 billion, whereas the needed resources to avert this loss is US$ 2.4 billion per year for the next 20 years. Unfortunately, there was not much progress on the implementation of the recommendations of the PACD, since it was not a binding document and the financial resources allotted to desertification control activities within the international aid schemes were quite limited. At the same time, the national governments in many concerned countries did not include desertification control activities within their development plans. The UNEP assessment for the period 1984 to 1992 showed that desertification was still spreading and that the world effort to combat it was short of being effective. It was estimated that income forgone due to desertification was around US$ 42.3 billion/year.

In view of the gravity of the problem, the whole issue was discussed in the UN Conference on Environment and Development (UNCED), also known as 'Earth Summit', held in Rio de Janeiro, Brazil in 1992. The Conference produced an action oriented document known as "Agenda 21" - a global blue print for environmental action that revolved around seven themes, one of which is "efficient use of natural resources of land, water, energy, forests and biological resources" and calls on countries to adopt national strategies for sustainable development (NSDS) that should build upon and harmonize the various sectoral (economic, social and environmental) policies and plans that are operating in the country. This is unquestionably the theme for the survival of humanity and for the sustainability of future agriculture. But, it seems that the time is running out and the implementation of this agenda is still a pious hope.

In this endeavor, the National Research Council, National Academy of Sciences, USA in its report on "Our common journey- a transition towards sustainability" concluded that human needs over the next two generations can be met while sustaining the earth's life support systems. But this will require the political will to support the creation of new knowledge through science and technology and a commitment to turn that knowledge into action (National Research Council, 1999). The report sets forth a new research agenda for sustainability science and calls for a linkage of scientific research and private actions to public policies. The report also outlined the greatest threats to sustainability and several priorities for action over the next two generations. Subsequently, the UN General Assembly resolved in the same year to establish an Intergovernmental Negotiating Committee for the Elaboration of an International Convention to Combat Desertification (INCD) and an acceptable convention was reached by consensus in Paris in June 1994 named as United Nations Convention for Combating Desertification (UNCCD). It comprised a framework of general principles and an operative instrument which includes four different Annexes for Africa, Asia, Latin America, and the Northern Mediterranean Countries. The convention placed strong emphasis on a "Bottom-Up" approach and the role of local participation in decision making. For this innovative and complicated process to work, awareness campaigns were organized to inform people at all levels about the new opportunities of the convention, thus resulting in global awareness of "Agenda 21- a comprehensive programme for global action in all areas of sustainable development". In evidence to these commitments, governments signed three legally binding conventions, the United Nations Framework Convention on Climate Change (UNFCCC), UN Convention on Biological Diversity (UNCBD) and Convention to Combat Desertification (UNCCD). The CBD set into motion the actions to place biodiversity at the centre of global, regional and national efforts for sustainable development and poverty eradication.

Subsequently, in 2002 the World Summit for Sustainable Development (WSSD), held in Johannesburg, South Africa urged states not only to take immediate steps to make progress in the formulation and elaboration of national strategies for sustainable development (NSDS) in terms of its five elements i.e. water, energy, health, agriculture and biodiversity (WEHAB) but also to begin their implementation by 2005. In addition, integrating the principles of sustainable development into country policies and programmes is one of the targets contained in the United Nations Millennium Declaration to reach the goal of environmental sustainability. In his regards, the eight Millennium Development Goals (MDGs) were set for sustainable development, wherein agriculture has an important role to play in meeting the three of these eight MDGs- (1): eradicate extreme poverty & hunger, (7): ensure environmental sustainability and (8): develop a global partnership for development. As a result of WSSD, Global community is currently paying renewed attention towards sustainable development for inclusive growth and better livelihood of resource poor people around the globe.

II. Global Congress on Conservation Agriculture

The Food and Agriculture Organization of the United Nations has been supporting the Conservation Agriculture movement globally in partnership with Consultative Group of International Agricultural Research (CGIAR), National Agricultural Research Systems (NARS) of different nations as well as other non-profit organizations. In this endeavor, the First World Congress on Conservation Agriculture (WCCA) was organized at Madrid, Spain during October, 2001 jointly by the FAO and the European Conservation Agriculture Federation (ECAF) wherein 70 countries shared the experiences on CA especially for resource conservation and improving the livelihoods. The following action plan was developed:

• A discussion forum should be quickly set up within the framework of FAO's Conservation Agriculture Workgroup

to facilitate and strengthen international exchanges, while avoiding invasive information,

• Subsequent contributions should be prepared for international conventions and events, such as the Agenda 21 and its conventions {Commission on Sustainable Development (CSD), UNCCD, UNCBD, UNFCCC}, the World Summit on Sustainable Development (WSSD), and

• A special synergy with the Kyoto Protocol should also be examined so that carbon sequestration via Conservation Agriculture could become a substantial incentive for its wider adoption.

Subsequently, the Second WCCA was organized in Brazil during August, 2003 with the theme of "Producing in Harmony with Nature". This Congress endorsed the declaration of the First WCCA and noted the remarkable advances made in the two years and came with the agreement that:

• Integration of CA practices with balanced and efficient application of modern agricultural methods is the principal road to sustainable agriculture leading to food, nutrition, economic and environmental security.

• CA can achieve food security by reversing soil degradation, reducing agrochemical use and contamination, improving food quality, and conserving, preserving and enhancing the quality of natural resources and biodiversity while increasing farmer's net income and competitiveness, and sequestering carbon from the atmosphere.

• CA is applicable to all sizes and types of farms and to all crops.

In this series, the Third WCCA was organized during October, 2005 by African Conservation Tillage network (ACT), Ministry of Agriculture of the Republic of Kenya and Kenya Conservation Tillage Initiative (KCTI) in association with New Partnership for Africa's Development (NEPAD) on the theme "Linking Production, Livelihoods and Conservation". The highlights of the congress were:

• It was felt strongly that CA contributed remarkably to poverty alleviation, food security, mitigating impacts of HIV-AIDS, natural resource management, and farmers' prosperity; and it is environmentally friendly farming system.

• In the development and adoption of CA, farmer participation should be empowered

• The multi-discipline/multi-stakeholder approaches, networking and collaboration (e.g. policies to interest/ facilitate private sector involvement) should be encouraged for innovative developments in CA and their wider scale adoption.

• CA should be linked with other global initiatives on sustainable agriculture and rural development.

• The Congress specially highlighted Africa's state of affairs with regard to issues and concerns including farmers' priorities for enhanced adoption of CA practices.

The current WCCA, which is Fourth in the series is being organized at New Delhi jointly by the Indian Council of Agricultural Research, Ministry of Agriculture, Government of India, National Academy of Agricultural Sciences (NAAS) of India, International Center for Agricultural Research in the Dry Areas (ICARDA) and FAO. It is indeed a timely and very important initiative. The theme this time is "Innovations for improving efficiency, equity and environment" which covers wide range of the Millennium Development Goals that are directly related to agriculture.

III. Global Partnerships

To address the issues of resource degradation, poverty alleviation and more recently climate change, various partnership programmes have been initiated by the global community. The partnership initiative on CA has emerged as one of the important strategy for meeting the challenges of MDGs and is currently being adopted on nearly 100 million hectares globally (FAO, 2008) with many success stories. In this respect, the Brazil has set a successful example of partnership for averting the events of serious soil erosion and land degradation through CA and took concrete initiative in 1962. In Brazil, CA emerged mainly as a result of partnership among farmers, input supply companies, state and federal research and extension organizations, universities, as well as long-term funding commitments from international donors such as the World Bank and German Technical Cooperation (GTZ). With new innovations through partnerships among CA champions, covering nearly 25 million hectares in Brazil, almost 45-60 % of agricultural land could be managed presently in South American countries (Derpsch, 2001). Similarly, in Sub-Saharan Africa, the Africa Conservation Tillage Network (ACT), established in 1998 to promote CA as a sustainable means to alleviate poverty, make effective use of natural and human resources and reduce environmental degradation has been a major champion for the establishment of a Pan African Network with global links and is currently active

in technology development, networking, information exchange and policy advocacy (ACT, 2003). A few successful

examples of partnerships related to conservation agriculture both at the regional and global level are mentioned

• In Asia, the intensively cultivated irrigated rice-wheat systems are fundamental to employment, income and livelihoods of hundreds of millions (Paroda et al, 2004), wherein evidences of exhausting the natural resource base under continuous intensive systems during post-Green Revolution period have also emerged (Gupta and Seth, 2007). Rice-Wheat Consortium (RWC) for the Indo-Gangetic plains of South Asia, an eco-regional initiative of the World Bank and subsequently CGIAR involving NARS of India, Pakistan, Bangladesh and Nepal was established with a goal to maintain food security and improve livelihoods of the farmers mainly dependent on rice-wheat production system focused specifically on deployment of resource conserving technologies (RCTs). For co-ordination of this eco-regional program, CGIAR provided annually around US$ 250000 since 2003. This program had also been supported under the National Agricultural Technology Project (NATP), by the Indian Council of Agricultural Research (ICAR) by allocating around US$ 1.5 million for a mission mode project on CA. With these investments and strong partnership and an innovative farmer participatory approach, the CA programme facilitated by International Maize and Wheat Improvement Centre (CIMMYT) in its version of RCTs, has now been extended nearly to 3 million hectares in South Asia (RWC, 2006, Gupta and Sayre, 2007). This success story of a regional initiative, involving global partnership, is known globally and had also received 'King Boudouin Award' from the CGIAR.

• A Global Partnership Program (GPP) on Direct Sowing, Mulch based and Conservation Agriculture (GP-DMC), an international initiative by Global Forum on Agricultural Research (GFAR) was launched in January 2000 and a Facilitation Unit was established, with support from CIRAD at Montpellier, France with the aim to strengthen the capacity of key stakeholders to develop suitable conservation agriculture systems and to accelerate their wide adoption in more than 40 countries with the support of stakeholders like CIRAD, CIMMYT, Agronomy Institute of Parana, Brazil (IAPAR), FAO, International Fund for Agricultural Development (IFAD), GTZ etc. Somehow due to resource constraint this initiative could not take off. Considering the importance of CA, GFAR facilitated in July, 2008 a working group discussion on research aspects of CA facilitated by CIMMYT, FAO and CIRAD. It reviewed the achievements of CA globally and actions required to accelerate the adoption of CA-based farming systems. A specific recommendation was made for the creation of a global partnership programme (GPP) as a cluster or network of inter-connected Communities of Practices (CoPs) with the aim to put in place and make operational a global initiative to promote CA for its large scale adoption in remaining potention areas. This way, a global focal point for CA would facilitate the operation of an international network aiming mainly at the application of CA for knowledge, advocacy, education and sustainable agricultural development. This GPP on CA, under the umbrella of GFAR, would aim to have a multi-functional website and a multi-disciplinary register of CA expertise. The major focus would be on knowledge sharing, capacity building and partnership building for faster adoption of CA practices for greater impact.

• Central Asian Countries Initiative for Land Management (CACILM), a multi-country and multi-donor partnership, was initiated in 2003 to support integrated and consistent approaches for investing in sustainable land management (SLM) practices in each of the countries of Central Asia over a period of the next 10 years. The ten-year investment program is divided into three phases (2006-08, 2009-13, and 2014-16, respectively) and its initial structure envisages a total investment of about US$75 million partly by the Government and donors (including a co-financing by GEF of about US$14 million) to complement investments made by the Program's target beneficiaries. This programme is expected to increase over time the CA activities in the region, for which great potential exists.

• The Forest Carbon Partnership Facility (FCPF) announced its expansion from 20 to 30 developing countries to support capacity building efforts to reduce greenhouse gas emissions by reducing deforestation and forest degradation (REDD). Developing countries are working with 11 industrialized countries and one non-governmental organization through this innovative partnership and international financing mechanism to combat tropical deforestation and climate change. The FCPF is comprised of two components- a Readiness Fund and a Carbon Fund. The World Bank acts as the secretariat for the FCPF. Its focus is to promote CA practices in protected forest to arrest soil degradation,

The global conventions and partnerships discussed in this paper are mainly focused on the land degradation,

poverty alleviation, climate change and over all sustainable development. The conservation agriculture strategy

aimed to revert the land degradation, improve carbon sequestration and reducing GHG emissions has a direct bearing on the MDGs. Therefore, various conventions and partnerships, aimed mainly to promote conservation agriculture practices, have helped greatly in managing our natural resources for sustainable development. Concerted efforts are, however, needed to promote CA globally in order to reap much greater benefits in the future.

References

ACT. 2003. Newsletter, 21 November, 2003. Harare: University of Zimbabwe and the African Conservation Tillage Network.

Derpsch, R. 2001. Frontiers in conservation tillage and advances in conservation practice. P. 248-254. In: DE Scott, RH Mohtar and GC Steinhardt (eds). 2001. Sustaining the global farm. Selected papers from the 10th International soil conservation organization meeting held may 24 24-29, 1999 at Purdue University and the USDA-ARS National Soil Erosion Research Laboratory.

FAO, 2008. Food and Agriculture Organization of the United Nations, AQUASTAT 2008

Gupta RK, and Seth A. 2007. A review of resource conserving technologies for sustainable management of the rice-wheat cropping systems of the Indo-Gangetic plains. Crop Protection, 26: 436-447.

Gupta, RK and Sayre, K. 2007. Conservation agriculture in South Asia. Journal of Agricultural Science, Cambridge, 145: 207-214.

Lal, R. 1997. Residue management, conservation tillage and soil restoration for mitigating greenhouse effect by CO2-enrichment. Soil and Tillage Research 43, 81-107.

Lal, R. 2004. Soil carbon sequestration impacts on global climate change and food security. Science 304, 1623-1627.

National Research Council. 1999. Our common Journey a transition towards sustainability. Board on Sustainable Development, National Research Council of USA. National Academy Press, Washington, DC, 363 pp.

Pandya-Lorch, R. 2000. Assuring food security and sound management of natural resources for the 21st century: the role of agriculture. (in): Proceedings of First International Agronomy Congress on Agronomy, Environment and Food Security for the 21 st Century, 2000. Panjab Singh, R. Prasad and IPS Ahlawat (eds). Indian Society of Agronomy, IARI, New Delhi, India.

Paroda RS, WoodHead T, and Singh RB. 1994. Sustainability of rice-wheat production systems in Asia. RAPA Publ. 1994/11, Bangkok : FAO.

Rice-Wheat Consortium (RWC). 2006. Research highlights 2005. Rice-Wheat Consortium for the Indo-Gangetic plains, 12th Meeting of the Regional Steering Committee of RWC, Varanasi, Uttar Pradesh, India.

Impact Analysis of Conservation Agriculture

S.S. Johl

Conferences, workshops, seminars, brain storming sessions etc. very often end up in written proceedings only. In most of the cases recommendations made and decisions taken do not get translated into field level actions or only symbolic actions are taken on a limited scale. It seems the Indian agricultural extension system is still suffering from the hangover of colonial past, wherein, " please the boss" remained guiding principle of the field level workers. A few well structured demonstrations, which may not have much impact or spread effect on the neighboring areas, are placed as show cases that create an ambience of action and adoption, wherein "boss-subordinate relations"do achieve some level of optimality.

Impact analysis or assessment is, unfortunately, the last priority that enters into the calculations of our policy makers and research administrators. There is lack of an explicit and effective built in system even in the country's National Agriculture Research System that would provide a reliable feed back on the effectiveness and impact of the research results when adopted on farmers' fields. Sporadic reports by individual investigations and organizations such as universities and research centers, do emerge that more often than not get consigned to the "seen and file" category and are seldom looked at again. These evaluations are not made an integral part of the research system to serve as eyes and ears of the research administrators or programme implementers. Such reports, based on well planned assessment, should serve the crucial purpose of reviewing the impact of research output on a continuous basis and these feed backs should be used to correct the pathways adopted in order to steer the research and extension programmes for optimal results.

Often the amounts spent under given heads out of the allocated funds are treated as achievements. This approach is wide spread in the extension and development activities of the government departments. For instance, the forestation and tree planting programmes end up with number of saplings planted and money spent. It is rare that survivals are checked/counted and financial and economic costs per plant or per hundred surviving plants are worked out after one, two or three years. It is sometimes noted that annual tree planting programmes like Vanmahutsavs get repeated at the same place. Similarly, demonstration plots are arranged on the same farms year after year with little impact on the neighbouring farms. Many often defective technologies are pushed through with the help of subsidies which in true sense do not find favour even with the farmers on whom these are directed.

The appropriate, useful and profitable technologies in fact need very little effort for their promotion. End users grab these opportunities spontaneously. I recall at one time the farmers stole a wheat variety seeds from the fields of the Punjab Agricultural University at gun point. Such research outputs get popularized within short time. Yet such examples are very few. Most of the appropriate technologies catch up within a couple of years and not-so-good technologies remain confined in their spread and fade out very soon.

In research, results do get evaluated at the level of departments and institutions. Even here, research outputs such as varieties, techniques, implements and other innovations are not evaluated or assessed that rigorously for their impact in respect of the extent of adoption, financial and social costs and returns, environmental impact and sustainability concerns. For instance, breeders generally get satisfied with the release of their varieties. Whether these are adopted by the farmers or not and to what extent, such aspects seldom get into their calculations. If research output does not catch up at the adoption level or fades out sooner than expected, the "why" is seldom inquired into. What economic, social and/or environmental impact it leaves, remains of little concern.

Not to speak of research and extension in the field of agriculture, the state level planning also suffers the same debilitations. Governments, both at the center and states, in the plan implementation consider the 'money spent' out of plan allocations as their achievements. It is not that provisions do not exist for making impact analysis or the assessment of physical output and externalities involved. In fact, quite a number of evaluation reports are written. The problem is that these evaluations do not make any dent on the mindset of the policy makers, planners and administrators. The caravan moves on at its own pace and in the same direction. This system, or lack of it, needs to be drastically revamped, reoriented and redirected at achieving optimality in the expected results and properly weighed against financial and economic costs along with positive and negative environmental externalities involved.

In the back ground of this scenario, the conservation agriculture practices and techniques need to be assessed in terms of enhancing/developing conservation and improvement in the use-efficiency of production resources in quantity and quality in order to provide sustainability to the production process on an upwards shifting production curve driven by the positive effects of improved techniques and technologies. The conservation practices have to be viewed in an all inclusive manner involving soils, water, environment, efficient use of resources, economic viability, equity issues and social implications. Our perception of conservation agriculture most of the time begins and ends up in zero tillage, because the practice has been accepted on a visible scale. As a result, other practices such as leveling, bunding, mulching etc, seem to have been put on the back burner and are operative at the level of demonstration plots mainly, that are maintained by the extension agents mostly at public cost as show pieces. No doubt zero-tillage has its own advatages in terms of savings on labour, costs and time, yet the purview of conservation agriculture goes much beyond soil and zero tillage per se. The Conservation Agriculture technologies must be synchronic in nature and more inclusive. Only then such techniques will come up with perceptible impact.

I would like to adduce a few examples of conservation agriculture practices, which deserve serious attention of National Agricultural Research System and Extension agencies. These technologies are amenable to impact assessment on the aspects of conservation and sustainability of resource use as well as their impact on soil health, water conservation, environment as well as economic viability for the farmers. Being size neutral, these are equitable in their impact.

First is aerobic cultivation of rice. Rice crop growing in ponded fields has serious negativities for soil quality, excessive application of scarce water and degradation of environment. On equity ground the system is less favourable for the areas and regions that have lower or limited water availability and also for small and marginal farmers, who either do not have their own means of assured supply of irrigation water or with heavier over head costs per unit of land used, it becomes comparatively more costly for them to grow rice under ponded conditions. There are a few alternative techniques developed by the Agricultural Technocrats in Punjab and by some scientists elsewhere, specially at Bangalore, which I have seen a bit more closely. From dribbling the paddy seeds or transplanting seedlings in flat fields in proper moisture to dribbling/pouring the seed or transplanting seedlings on bed-furrowor ridge-furrowsystems have all proved reasonably successful. These systems result in: (1) Water savings between 30 to 60 percent, because of controlled applications of water. A soil scientist at Punjab Agricultural University has estimated 66 percent saving of water in ridge-furrow system. In rainy season these techniques rather harvest the water and crop does not need to be irrigated for long periods. (2) the soil quality improves because no puddling is required to pond the water constantly. These techniques check the formation of hardpan in the soil. (3) Earthworms develop in the soil. (4) Micro-climate remains comparatively dry which lowers the incidence of insect pests and diseases.(5) Emission of green house gasses, specially CO2 and methane decreases drastically with favourable impact on environment. (6) Being size neutral, the systems are equitable for the small and marginal farmers. (7) There is considerable savings on labour required for transplantation. Since this operation of transplanting rice in standing water involves considerable proportion of female labour, these systems reduce the drudgery of work and is therefore in a sense gender favourable also.

Major problem of these systems of aerobic cultivation has been of weeds. However, pre-emergence and post emergence weedicides have now been developed/identified, which have tackled the problem completely. On yield, the average of twelve trials at the Punjab Agricultural University have indicated 7 percent higher yield compared to the paddy grown in standing water. These techniques are catching up fast with the farmers. Most accepted and updated technique today is that the field is prepared like the one is prepared for sowing of wheat with good moisture. The paddy seeds are broad cast and ridges and furrows are drawn two feet apart. While the field is in good moisture pre-emergence weedicide is applied. The field is left as such for the seeds to germinate. Normally no water is applied up to at least 15 days. As the plants show signs of stress, water is applied in the furrows. The frequency of the water application is at intervals of 7 to 10 days. In case of adequate rain, water is not applied for long periods. Rather the field remains in good shape to harvest the rain water. Post-emergence weedicide is applied only once at a threshold point, normally after thirty days of emergence. Weeds in that case serve the purpose of mulch, which further reduces the need for irrigation. Within a very short span of a few years the technology is expected to catch up with the farmers with perceptible positive impact on soil health, water use efficiency, environmental improvement, and economy of rice cultivation on an equitable basis. However, there is a need to develop reliable system of impact assessment within the National Agricultural Research System that works at the field level in respect of spread of such conservation techniques and positive and/or negative externalities that impact the farm economy, sustainability of production resources and agro-ecological environ of the country side. Some pictures of the system described above are attached as appendices.

The second, I would like to mention about is organic farming and traceability systems. There are many organizations, companies and individuals that are propagating organic farming of various shades. Yet there is no system in place that can reliably assess their results and impact on productivity, production, the farm economy, environment and sustainability of resource use. I have tried to look into the details of one such attempt being made by a company named International Sustainability Systems in collaboration with National Horticulture Mission, Indian Institute of Technology, New Delhi and INDOCERT. They have brought some fifteen thousand hectare of land in Utter Pradesh and three thousand hectare in Punjab under their system of organic farming. They prepare two cultures of micro-organisms isolated from the soils they take under their system. The cultures of micro organisms from soil isolates are prepared in collaboration with IIT New Delhi. The two cultures, inter alia contain the following organisms. Some other area specific organisms are also incorporated in these two cultures. Culture-I is primarily for fertilization and control of diseases like root rot, stem rot, leaf rot and soil borne as well as seed borne pathogens of the crops. Culture- II contains bio-pesticides against insect pests and bacterial diseases.

Culture-I Contains

i) Azotobacter spp

ii) Rhizobium

iii) Azospirillum spp

iv) Bacillus megaterium var. phosphaticum

v) Frateuria aurentia

vi) Paecilomyces lilacinus

vii) Trichoderma harzianum

viii) Trichoderma viride

ix) Pseudomonas fluoresens

Culture - II contains

i) Metarrhizium anisopliae

ii) Nuclear polyhedrosis virus (NPV) of Spodoptera litura

iii) Nuclear polyhedrosis(NPV) of Helicoverpa armigera

iv) Verticillium lecanii

v) Baillus thuringiensis var. kustaki, Steriotype H-3a, 3b,strain z-52

vi) Beaveria spp

For application of First Culture, a one kg packet of the culture is mixed in water with one kg of jaggry (Gur) and one kg gram (chickpea) flour. This mixture is then mixed with one quintal (100 kg) of cow dung and covered for seven to eight days. The culture prepared this way is sufficient for one acre of crop. This culture replaces the chemical fertilizers and controls the soil and seed born diseases as well as nematodes and root, stem rots. With this culture six to eight tons of farm yard manure is required per hectare of land for one year crop rotation. Thus, organic production can be extended to the extent the farm yard manure is available for application in the fields at this rate. The second culture is prepared the same way and put in drums of water. Some leaves of Neem (Azadirecta indica ) trees, Ak ( ) and/or Dhatura ( )plant. (if available) are added to this culture. Water is decanted and then cleaned of suspensions and applied as spray on crops. This culture is claimed to be controlling all the insect pests of crops, except weeds. The culture-1 is claimed to have controlled even Phyto-pathora of citrus plants and revives the plants if applied in early stage of the disease.

Their approach involves small farmers and small areas under the crops. Clusters of some 50 farmers with around 50 hectare of crop land are formed and a cluster- in-charge is made responsible to train, guide and monitor the activity. A printed note-book is provided to the registered farmers, who are required to note down whatever they do to the field and the crop registered. Every farmer is assigned a code number in record with the National Horticulture Mission. Some samples of clusters in Utter Pradesh and Punjab are given in appendices. The area/crop under organic farming is marked as C1 in the first year (Under Conversion year one), C2 in the second year and C3 in the 3rd year. Internal control is excercised by the ITS and external control and verification is done by the INDOCERT. Organic production is certified only after three years. In the first year and second year the farmer can, on his own. make a statement that, "No chemical fertilizers or pesticides are used in this product". This statement is not, however, certified by the ITS/Indo-cert. The economic analysis of some the crops of the farmers in Punjab, who adopted organic farming is produced in the appendices.

It is observed that the system adds to the organic carbon content of the soils that are put under the system year after year. One year analysis is given below:

I.D Number Farmer's Name Village Crops Organic Carbon Organic carbon Difference*

before crop After crop

INPBHO08ORG01 Lakhwinder Singh Bhikhwal Kinnow- Inter crop: Tinda, Maize, Potato 0.65 0.72 0.07

INPBHO08ORG05 Jagir Singh Bhunga Kinnow-Inter Crop: potato maize 0.30 0.75 0.45

INPBHO08ORG52 Mohinder Singh Hariana Potato. Maize, Peas 0.45 0.69 0.24

INPBHO08ORG79 Mandeep Singh Bohn Potato,Chillies, Carrot 0.39 0.66 0.27

INPBHO08ORG141 Gurdeep Singh Kantian Kinnow 0.51 0.69 0.18

INPBHO08ORG300 Santokh Singh Chak Gujjran Potato, Maize,

Peas 0.60 o.75 0.15

Source: Analysis was got done from the Punjab Government Laboratories.

*Difference in organic matter was worked out on the basis of soil analysis done before the start of the Organic farming programme in Nov.-Dec. 2007 and after the crop rotation was over in Nov. 2008

The analysis is indicative of the improvement in organic content of the soils through adoption of organic farming. The strong point of this system is that micro-organism are the isolates from the regional soils and are mostly area/ location specific and multiply quickly in the environ they belong to. Second important aspect is that micro-organism multiply quite speedily in the highly conducive medium created by the mixture of cowdung, jagary and gram flour, which makes it possible to apply the useful micro-organisms culture in the field in substantial quantity.

The ITS and their collaborators have a programme of introducing traceability through preparing and issuing of bar codes that can be pasted on fruits and vegetable packets and even on individual fruit like Kinnow, mango or apple, which can go a long way in fetching higher price in the high end national and international markets.

Yet, this system of organic farming and other ones propagated and promoted by various organizations and NGOs need to be evaluated on a continuous manner through a recognized and accredited system created within the National Agricultural Research System at the central and state levels through the ICAR and the State Agricultural Universities. Unfortunately the Organic Farming approach, which has a potential to revive the soil health, improve agro-ecological environment, save on input costs, realize higher prices of the organic products and improve nutritional security are often out rightly rejected by the scientists of the National Agricultural Research System of the country. There is, therefore, also a dire need for change in the mind set of agricultural scientists of the country in this respect.

Theme 1: Resource Productivity and Efficiency

No-Till System Applied to Northern Africa Rain-Fed Agriculture: Case of Morocco

Oussama EL GHARRAS1, Azeddine EL BRAHLI2 and Mohamed EL MOURID3

1Ag. Eng. Laboratory, INRA-Settat, P.O. Box: 589, Settat, 26000, Morocco (Email: o_eigharras@yahoo.fr ) 2Weed Scientist, Consultant, Rue 11 Janvier, Al Kahir, Settat, 26000, Morocco (Email:

aelbrahli@hotmail.com) 3Regional coordinator North Africa-ICARDA, 1 Rue des Oliviers ElMenzah V, 2037 Tunis

(Email: melmourid@yahoo.fr)

Rain fed agriculture in North Africa is facing the challenge of balancing between natural resources preservation and intensive farming systems. In Morocco, analysis of thirty years of weather data showed a drastic climatic change threatening crop production. The total rainfall amount received is low to support enough grain production in order to cover increasing needs for food and feed growing population and high number of animals. The water scarcity is exacerbated by alarming land degradation from conventional tillage operations and heavy animals grazing of biomass grown or left as crop residues on soil surface.

Research in Morocco investigated over 25 years, conservation tillage systems at experimental research stations. Different tillage combinations were compared to no till with different rates of cereals crop residue, crop rotations and weed management. Results showed that the no-tillage system offers most sustainable way to enhance resources productivity, water productivity and water use efficiency, soil quality and better cost effectiveness.

At farmers' fields complex and well established relationships are integrating crops and livestock as a way to face high variability of climate. This production system makes grain production and crop residue of equal value. Conservation Agriculture principles based on residue and cover crops well demonstrated at research stations, become very difficult to apply especially during drought seasons when animals survival turn to become farmers major priority.

During the last decade, and building on encouraging research results, direct seeding was scaled out to farmers' fields and has led to a better understanding and adaptation of this promising system to Moroccan and North African rain fed agriculture production systems. Applying on-station research results in the farmers' fields resulted in a hybrid no- till system with no threshold of surface residue cover; but with whatever was left and accumulated over years after hand removing and grazing.

This paper reports results over ten years of on-farm research under rain fed conditions in semi-arid Central Morocco (Lat. 34 N.). Results obtained in farmers fields showed in all cases higher yields under drought conditions and higher or equal under normal conditions. These achievements might be attributed to (i) a well adapted cheap and locally developed no- till drill. (ii) Water conservation techniques that allowed more crop production stability. (iii) Simplification of wheat crop establishment with no additional costs of tillage or pre-planting weed control and (iv) Cost effectiveness.

The success of this research is credited to full participation of farmers' communities and to a strong scientific multidisciplinary team along with real involvement of extension agents and local authorities.

Key words: Water conservation, Soil degradation, No-Till, Cereals production, Crop residue, Morocco.

Morocco and North Africa in general have a Mediterranean climate with hot and dry summers, cold and rainy winters and scarce autumn and spring rainfall events. Studies on climatic changes over 30 years period in Morocco showed a trend of drought periods that can occur at any time during the growing season demonstrating the highly erratic annual rainfall distribution (El Mourid et al, 1993 and BenAouda, 2001) (fig. 1). The total amount of rain is decreasing significantly reducing the growing season from 180 days in the sixties to 150 days in the nineties (BenAouda, 2001) (fig. 2). Variability in crop production, mainly cereals, follows the rainfall pattern. Moroccan cereals production varied from 10 millions tonnes in 1996 to 2 millions tonnes in 2006 that was mainly produced in irrigated fields. Average rainfalls recorded in Settat, one of the main cereals production regions, were 450 mm and 150 mm respectively for these years. Frequency of drought that was one over five years becomes one in every two to three years (Yacoubi et al, 1998). In addition to limited water availability increase in temperatures are observed and lead to high evapo-transpiration rate increasing water deficit. Every year drought is affecting at some scale crops and animal production but severely when it occurs successively several years. Any produced biomass; straw, crops residue or hay, reaches maximum market value. Morocco government has the challenge to raise funds to import wheat and forages to feed the growing population and livestock. Number of estimated animals is 15 millions sheep, 5 millions goats and 3 millions cattle that use 49% part of their food requirement from grazing and crop residues (Nefzaoui et al., 1999). Straw has also other important uses such as chicken and cattle bedding.

Session 1.1: Soil and Residue Management

Straw price in dry years can reach as much as 0.15 dollars/kg. In all conditions and all over the Moroccan territory, cereal crop residues left after harvesting and baling are the main source available to overcome the animal needs through summer time. On the other hand, in high rainfall regions, after successive good cropping years, excessive crop residues left over on soil surface may become a problem for tillage operations and are burnt.

Introducing no till in this production system seems to lack one of its fundamentals requirements that are residue cover. In the present paper we will discuss the limits of modern conventional agriculture based on intensive tillage, continuous cropping system and total export of plant biomass. Review key research finding obtained under no till system as the proposed alternative and the efforts made to reach the farmers and the constraints to succeed the establishment of No-Till system in Morocco.

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Figure 1. Rainfall evolution in Settat (BenAouda, 2001)

Growth peiiode length at : KhourBiga 1960-65

Figure 2. Growth period length for cereal production in dry land central plains (32° 51 N, 6° 54 W), BenAouda, (2001)

Conventional Management

Autumn Sown Field Crops

Cultivation starts with summer intensive tillage that has been synonymous to farming performance. The main used tools are stubble plow, disc harrows and chisel. After harvesting, baling straw and grazing the remaining

residues for four to five weeks, fields are subject to tillage operations. It is believed to improve soil moisture conservation by retuning the soil up side down and eliminating soil cracks. In autumn, just before planting, fields are again disked once or twice to reduce clods size, control weeds, mix the fertilizer with the soil and prepare seed bed.

Rainfall events, optimum planting date and tillage operations for seed bed preparation are the most difficult crop management to deal with in order to succeed crop establishment. First significant rainfall has a random occurrence and late rainfall hold farmer from planting in dry condition. Soil needs several disking or particular equipments such as rotavator or compactors not available in Moroccan farms to obtain a good seedbed. Waiting for rain to prepare seed bed can delay planting and expose crop to end season grain filling water and temperature stresses then risk of low yields. In wet years with early season rainfall, tillage operations are conducted in wet conditions resulting in soil compaction, run off, and soil erosion.

In general, the offset disk is the dominant tool for seed bed preparation. Sowing is accomplished either by drill or broadcast seeds by hand and cover with the offset disk. This seed soil mixing and covering results in uneven seed repartition and non uniform seeding depth. Part of moisture is lost by evaporation and run off caused by formation of hard pan that reduces water infiltration. In order to obtain adequate plant stand farmers increase seed up to double or triple the recommended rates.

Spring Sown Field Crops

In high rain fall areas, field reserved to spring crops such as sunflower and chick pea, are subject to deep tillage in summer time and several shallow tillage operations in the rainy season. Farmers use the mouldboard plow in order to control adequately weeds and have fields ready for seedbed disc harrow in spring time. Repeated tillage operations at a time where chance of rain is narrowed result in drying the top soil layer and increase risk of seed emergence failure. Temperature increase leads to high evaporation rates and crops are often subject to water stress that causes incomplete grain filling. Surface area of these crops is significantly decreasing placing the country on complete dependence on the importation.

The energy used in tillage is estimated to quarter of millions tonnes of fuel that its outcome could be null as in years 1981-83, 1995 and 2006 where almost nothing was harvested (Morocco Ministry of agriculture reports, 198183, 1995, 2006).

Common Cropping System and Residue Management

Crops and livestock are integrated in complex production system mainly to manage drought risk and uncertainty of grain production. This integration is stretched with rainfall scarcity and shallow soils. Beyond social and economic consideration, the cropping system is dictated by the average annual rainfall and the nature of soil and its water storage capacity (Table 1).

Table 1. Common crop rotations for different agro climatic conditions

Soil depth Rain fall in mm

less than 300 300 to 400 more than 400

Deep soil Shallow soil wheat /fallow continuous barely - wheat/wheat/fallow or - wheat/wheat/ faba bean or spring chick pea - wheat/forage - wheat/lentils - wheat/wheat/Sunflower - wheat/wheat/winter or spring food legume - wheat/forage crop - continuous wheat

In dry areas (less than 300 mm) with deep soils farmers have adopted clean fallow with intensive tillage through the season to save moisture. However, (Bouzza, 1990) and (Kacemi, 1992) found that water conservation in this system does not exceed 15%. When rainfall exceeds grain production threshold (around 300 mm), continuous cropping is more common. Crop rotation based on cereals is either continuous cereals break down by fallow or in rotation with food legume, forage or spring crops such as chick pea and sunflower.

Harvesting is done to get out both grain and straw yields. In high production years, straw is baled and fields are subject to animal grazing. Despite the amount of residue removed, more than one tone per hectare is burnt or tilled.

In years of low rainfall or in more arid areas, crops have dual purpose, they can be harvested for grain as well as grazed by animals when farmers are dispirit in getting grains. Fields are completely swiped and only wheat plant crown and roots are left. Rent fields for crop residue grazing is common attitude for farmers that do not have livestock or when fields are far a way from the farm's buildings. Food legume crops are rarely combine harvested instead plants are pulled with their roots exporting 100 % of the crop biomass.

Cost effectiveness of this farming system in terms of energy, inputs, risk of drought and decreased yield due to land degradation discourage investment in dry land agriculture.

No Till System as Alternative to Conventional Farming

Research all over the world has shown that conventional tillage causes considerable damage to the soils. Repeated tillage operations can induce greater soil erosion and moisture losses. The soil clods once broken into small particles become susceptible to be easily transported by wind or water, especially when soil surface is not protected by residues cover. To alleviate these problems and also to save on labour and energy inputs, conservation tillage practices based on direct seeding have become an alternative to conventional tillage. After the three years of severe drought in the early eighties, Moroccan research has addressed the issue of water conservation as one of the main rain fed research program. Highlights of related results are outlined in the following.

Water Conservation

The main objective of water conservation is to reduce evaporation and increase soil moisture conservation by eliminating tillage and keeping part of the crop residues on soil surface. Indeed, different tillage equipments and timing periods were compared to no till in continuous wheat and wheat/fallow rotations (Bouzza, 1990 and kacemi, 1992). Table 2 shows that chemical fallow and no till wheat rotation gave higher production than continuous cropping. The most important feature is the stability of wheat production instead of the sawtooth trend in conventional tillage.

Table 2. Effect of cereal rotation and tillage on wheat yield in t. ha-1 in experimental stations; Sidi El A'di and Jemaa Shim. (Bouzza, 1990 and Mrabet, 2000)

Type of tillage Sidi El Aydia Jemaa Shaimb

Wheat-wheat Wheat-fallow Wheat-wheat Wheat-fallow

No-till 1.9 3.5 1.7 3.0

Minimum till 1.6 3.4 1.5 3.0

Conventionnal tillage 1.4 2.4 1.6 2.4

aAverage grain yield 1983-1992 in clay soil Vertisol, average rainfall 370mm. bAverage grain yield 1983-1998 in caly soil, Vertisol, average rainfall 270 mm.

Keeping residue on soil surface is known to reduce soil evaporation. Soil can keep its moisture in seed zone up to 5 weeks above the wilting point where it remains only 15 days in tilled plots compare to no till ones with residue cover (Mrabet, 2001). Table 3 shows that water storage efficiency is 1.5 times higher under chemical fallow than under clean fallow (Bouzza, 1990). An average of 84 mm stored in soil profile, instead of 30 mm in weedy fallow, has been saving the cropping season from a mid season water deficit and ensure production stability with all advantages in budget, food security planning and price constancy..

Table 3. Storage efficiency and amount of stored water for different types of fallow in semiarid of Morocco. (Bouzza, 1990)

Type of fallow Storage efficiency* (%) Amount of stored water in 1.2 m profile in mm

Chemical 28 84

Clean 18 54

Stubble mulch 21 63

Weedy 10 30

* Calculated as the ratio of stored water and the rainfall received during fallow period.

Carbon Sequestration and Soil Aggregate Stability

In experimental field, at Sidi El Ai'di research station, where crop residues were left on soil surface, at 0-25 mm, soil organic carbon (SOC) increased from 5.62 to 7.21 t/ha under NT, after 4 and 11 years. At the same horizon, SOC level did not change under conventional tillage after the same periods (Bessam and Mrabet, 2003). These authors reported that NT soil has sequestered 3.5 and 3.4 t/ha of SOC more than conventional tillage in the 0-200 mm horizon, after 4 and 11 years, respectively. These findings are illustrated in Fig. 3. Over the 11 years, the 0-200 mm horizon gained 13.6 and 3.3% of its original SOC under no-till and conventional tillage, respectively. The NT improvement of SOC is also proportional to residue level. Increase in residue level helped sequester the greatest amount of C in the top 50 mm of soil, a lesser amount in the 50-100 mm depth and no significant amount in the 100-200 mm (Mrabet et al., 1999).

B Nd hit □ Co nvc n tl E no I

Initial After 4 yü n n A'tur II y ears

Figure 3. Soil organic carbon in 0-200 mm horizon as affected by tillage system and time (Bessam and Mrabet, 2003)

The Moroccan soils are vulnerable to erosion by water and wind due to their low organic matter content and poor aggregation. Independently of the season, results showed that the proportion of more stable aggregates in the soil surface (seed-zone) is greater in NT than conventional tillage. It was also found that aggregate stability increases with depth as residue cover increases in NT. The development of a good structure at the surface improves water infiltration, movement and distribution and has positive effects on evaporation and erosion control. The aggregation also reflects that SOC is conserved and protected and allows soil organic matter to function as a reservoir of plant nutrients and energy. (Mrabet et al., 1999)

Weed Management

Weed management remains world wide main no till system challenge. In Moroccan dry land, weed emergence depends on the first significant rain. Elbrahli and Mrabet, (2000) reported that, when optimum seeding date overlaps with the first rain, pre-planting herbicide application may not be required since weeds are not yet emerging. However, early post-emergence before tillering is recommended to control the flush of weeds emerging simultaneously with the crop. In years with early rain pre-planting treatment with non selective herbicides is a prerequisite to crop establishment success. A complete crop loss can be observed in fields that herbicide treatment failed to give a good weed control. Long term experiment shows that in one over five years pre-planting treatment is performed. In wheat-fallow rotation, clean chemical fallow is obtained with two applications using non selective herbicide. First one is at planting time and the second is done in late spring season. Chemical weed control in food legume, faba bean, lentils and chick pea are not available. The same above authors recommend that in no till system, delay planting of these crops and use of non selective pre-planting herbicide reduce the weed infestation to a threshold of insignificant yield losses. In these conditions, hand weeding in mid season to obtain complete clean food legume fields requires far less labour than conventional cropping estimated to about one over five.

It appears that in Moroccan dry land farming, no till system does not rely much on the intensive use of herbicides like elsewhere. Weed infestation decrease in the long term shifting to some perennial weeds such as Arizarum vulgare, cynodon dactylon, Ecbalium elaterium, and Ornithogalum narbonens. Frequent hand removing of these sporadic

species as they appear in the field can keep their population under control without economical crop losses (Elbrahli and Mrabet, 2000).

In low rain fall areas, weeds are considered as forage for animal. Weedy fallow reserved for animal grazing can get up to 25% of land use. Farmers would like to keep a biodiversity of plant species on their fields. In these environment, the use of non selective pre-planting and post-emergence residual herbicides recommended for the intensive cropping, is replaced by a gentle hormone selective herbicides that give poor control of some legume species such as Astragalus boeticus, Vicia sativa and Medicago spp. The planting of forage crops such as oats on emerged weed seedlings is allowed to increase plant biomass and also keep the biodiversity of this frail ecosystem.

Locally Manufactured No-till Drill

Grain drills for no-till have several soil engaging components and have to operate in untilled, compacted and residue covered soils, thus they must be heavily constructed to provide penetration in these conditions. The success of no-till seeding depends largely on the performance of the coulter, the opener and the press-wheel. The Moroccan soil conditions at seeding time are generally dry, compacted due to animals grazing and contains only small pieces of the left straw and roots. Bahri (1992) tested three combinations of furrow openers in different soils and conditions. He concluded that the hoe opener created a deeper and larger furrow creating more soil disturbance compared to single disc and double disc openers. He also, reported that the hoe opener gave better results in newly converted soils to no-till under the hard and dry conditions of soils during planting season. The grain drill developed in Morocco is a three point hitch machine of 2 to 3 m effective working with. The furrows spacing is 20 cm. The coulter is used to cut through residues and prepare the furrow for proper seed placement by the opener in order to avoid the jam of residues in front of the opener and poor germination that may occur if the seed is placed in a trashy zone with too little soil-seed contact. The coulter is a 45 cm diameter notched disc and each coulter is individually spring loaded and mounted on the main frame. The side to side movement of the coulter is adjusted by a swivel lock and allows the coulter to swing and over come the obstacles (rock and stones) with no damage and clear the way to the opener. The hoe opener operates in line with the coulter to aid in opening the furrow in which fertilizer and seeds are placed. The fertilizer lands at the bottom of the furrow in a depth superior to seeds through an independent rectangular tube. The seeds are placed 1 to 2 cm above the fertilizer. The hoe opener requires less vertical force in order to improve penetration and creates the necessary needed soil disturbance for good seed-soil contact. The press wheel is used to cover and compact the soil around seeds. In dry soils with low organic matter and poor aggregation, the use of a rod behind the press wheels improve seed cover and flatten the soil surface.

Figure 4. Scheme of the engaging components of the Moroccan seed drill

Introduction of No-Till Technology to Farmer's Fields

Introduction of no till system to farmer fields started in 1997 in Chaouia area where 15% of Moroccan cereal is produced. This region is characterized as an intermediate to low rainfall zone. Deep clay vertisols as well as shallow calcixeroll and silt clay fertialitique are common soil types where the INRA prototype drill was tested. Cropping system was established in common agreement with the farmers depending on the agro ecological and the prevailing cropping system. In all sites crops and livestock were of equal importance. Baling and removing crop residue were systematically done. Farmers' animals as their neighbours' were grazing along summer season up to the first rain where residue

Figure 5. Photo of the Moroccan seed drill operating at farmer's field in the first year introduction of the no till system. The drill is operating on dry soil with high percent of stones and no residue on the soil surface. (El gharras et al., 2004)

becomes not appropriate for grazing. The resulted amount of residue left never exceeds a tone per hectare. In fact the remaining amount of residues is increasing and decreasing as the wheat production. The drill gave a good stand establishment for all cereal crops as well as lentils, vetch and chick pea except broad bean that its seed size need no till planter for a good seed distribution. Even with the small amount of residue change of soil aggregation by the accumulated organic matter was observed (Fig. 6).

L uinvncicvihillPKr Ntnll jfer J year*

Figure 6. Soil surface at farmer's field after 25 mm rainfall

Performance of no till even with low amount of residue is mainly due to water and nutrient use efficiency during the cropping season. Water stored in fallow was beyond the 30 cm depth (Bouzaa, 1990). Soil types with cracking characteristics left without tillage is suspected to improve water storage by increasing infiltration even with small residue amount. Also, slight decrease in the high pH of calcareous soil coupled with concentration of fertilizer placement one to two centimetres below the seeds, possible with Moroccan no-till drill, enhance nutrient availability (Saber and Mrabet 2002).

Increase in insects, arachnids and other fauna up to become a problem, is a change noticed in long term no till fields, hence contributing to increase cavities in the soils and thus the rate of water infiltration.

In ten years period, pre-planting non selective herbicide was applied only three times. Planting over weeds at seedling stage was fallowed by early post-emergence herbicide at three leaves wheat stage to prevent weed competition. Crop rotation and animal grazing on fallows prevent the establishment of grass species in cereals and made the use of

cheap broadleaves herbicides of non additional cost to the farmers. Grain yields reported in (fig. 7) from no till pioneer farmer field show the increase yield obtained in dry as well as in wet years. In very dry year where less than 200 mm were received farmers were able to produce 1.1 and 1.5 tonnes of wheat in two different locations where the no till fields were the only ones harvested in the entire region. Straw production has been also improved. Farmer was able to produce in years where straw is a precious commodity. That was the case in 1999 and 2000 where farmer manage to harvest 1 and 1.5 tone per hectare respectively (El Brahli and Mrabet, 2000). In wet years, change on farmer perception toward residue left in the field as an investment in his soil rather than wasted biomass, were noticed by setting up the cutter bar of the combine to leave more residue in the field. Nefzaoui et al. (1999) reported that the amount of crop residues is greatly affected by amount of rainfall and nitrogen fertilizer than cereal species or varieties within species. However, barely straw is highly appreciated and consequently, less crop residue is left from barely fields compare to bread or durum wheat ones.

Figure 7. Grain yield at farmer's field under conventional and no-till (EL brahli and Benazouz. 2004)

No till water conservation on wheat and chemical fallow rotation were shown, as in experimental stations, to be able to reach grain production stability and offer some straw and plant residue on years where nothing was available for starving animals.

No Till Program of AAAID and INRA in Morocco

Recently a new no till system development program is initiated between the AAAID (Arab Authority for Agricultural Investment and Development) and INRA - Settat. New drills from Brazil (SEMEATO) were imported to support this

Table 4. Energy and time requirement for different tillage practices (El Gharras et al. 2004)

Power (hp/m) Time (h/ha) Fuel consumption (l/ha) Number of passes

Conventional tillage 100 to 140 6.5 to 8.5 31 to 45 4

• Deep tillage 50 - 70 3.0 - 4.0 10 - 15

• Secondary tillage 20 - 30 2.0 - 2.5 10 - 12

• Seed bed preparation 15 - 25 1.0 - 1.5 6 - 8

• Seeding 15 0.5 5

Reduced tillage 50 to 70 3.5 to 5.0 21 to 25 3

• Stubble plowing 20 - 30 2.0 - 3.0 10 - 12

• Seed bed preparation 15 - 25 1.0 - 1.5 6 - 8

• Seeding 15 0.5 5

Minimum tillage 30 to 40 2.0 to 2.5 11 to 13 2

• Disc harrowing 15 - 25 1.0 - 1.5 5 - 8

• Seeding 15 0.5 5

No-till 25 to 35 0.6 to 1.0 5 to 7 1

program and test their performance under Moroccan soil conditions. Approximately 1200 ha were planted using these machines and the locally manufactured drills during the cropping season 2007-08. About 80 farmers subscribed to this program most of them are at least in their second year. Project provides recommendations and guidance for farmers. Performance of both drills is excellent in clay vertisol and calcixeroll soil types. However, the SEMEATO was not able to offer the necessary penetration in fields presenting high percent of surface stones, discs are rolling over the rocks and seeds remain not covered. We also notice that farmers are manipulating these machines that need more care in term of driving speed and maintenance as they do with conventional drills. Similar remarks could be made in crop management especially concerning weed control that should be timely scheduled and adequately accomplished.

In the first years farmers are much more pleased with the saving of energy and time spend in crop establishments. Indeed, farmers can save as much as 40 litres of fuel per hectare and cut on labour and seeds expenses. Saving in equipments, seeds and labours are all short term motivations for farmers that experience for the first time this cropping system. However, natural resources conservation and improvement are the main objective to achieve.

Conclusions

Farming in rain fed areas of North Africa is a high economic risk activity. Intensive natural resources mining and continuous degradation of soil fertility under conventional agriculture practices will not ensure farm productivity and food security for the coming years. In order to keep cereal production systems sustainable, conservation agriculture based on no till system seems to be the alternative to conciliate agriculture with its environment and overcome the imposed constraints of the climate change and continuous increase of inputs cost. The slight increase in water conservation and water use efficiency obtained by no till system has tremendous effect on yield improvement and production stability in Moroccan agriculture environment. Even though, crop residues have high value and small amount is left after harvesting, a build up over years and change in farmers' behaviour toward residue management as a long term investment on soil quality has been noticed on established farmer's fields. More over, improvement of grain and straw production encourage farmers to leave more residues on their fields and ensure the long term benefit of no till system.

Participatory management approach and on farm demonstrations that succeeds in simple technologies development and their scale out seems to have slow impact on the adoption of no-till farming system. Innovative development approach need to be implemented by activities such as: a) intensive guidance of farmers in order to change the heritage accumulated over years of conventional farming. b) On-job training and development of agriculture enterprises for planting and weed control renting their service to farmers is a practical issue for the adoption of this production system. c) Subsidies allocated to different farm machinery should be withdrawn toward no till technology.

Capital investment is required to boost the cereals production chain toward natural resource conservation. Needed also are the involvement and collaboration of international agencies and institutions such as AAAID development program's in the Arab countries that is willing to invest in conservation agriculture in order to improve farming efficiency and environment quality. Local manufacturing of No-till drills can also be a pillar to enhance private capital investments to play a major role in adoption of no-till system. Recent national developed strategies for Moroccan agriculture encourage the aggregation of small farmers around an aggregator in a production chain where no till system can play a major role in gathering farmers around a common interest.

Acknowledgements

The authors would like to express their recognition to INRA who supports the long years of research, and AAAID that provided, during the last two years, assistance to scale out research results.

References

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Bessam, F. and R. Mrabet. 2003. Long-term changes in soil organic matter under conventional and no-tillage systems in semiarid Morocco. Soil Use & Management 19(2):139-143.

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Saber, N. et Mrabet, R. (2002). Impact of no tillage and crop sequence on selected soil quality attributes of a vertic calcixeroll soil in Morocco. Agronomie, 22 : 451-459.

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Critical Research for Dryland Conservation Agriculture in the Yellow

River Basin, China: Recent Results

Yan Changrong12, He Wenqing12, Mei Xurong12, John Dixon3, Liu Qin12, Liu Shuang12, Liu Enke12

11nstitute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural

Sciences (CAAS) , Postal 100081, Beijing, China 2Key Laboratory of Dryland Farming and Water-Saving Agriculture, MOA, Postal 100081, Beijing , China 3International Maize and Wheat Improvement Centre (CIMMYT), Apdo. Postal 6-641, 06600 Mexico, D.F.,

Mexico

(Corresponding author: meixr@cjac.org.cn)

Yellow River Basin (YRB) is the cradle of Chinese civilization. Agriculture production plays a very important role in regional food security. Currently, soil erosion, poverty and water shortages are three major problems that affect the development of agriculture in YRB. Severe soil erosion is leading to loss of fertile topsoil and decreasing soil productivity. These processes are particularly evident in dry and sloping lands associated with rainfed agriculture. How to face and resolve these problems in agriculture? And what are the key techniques to improve rainwater use efficiency? According to the results in the drylands conservation agriculture research and practice, CA is the most promising approach for sustainable development in agriculture, such as harvesting of rainwater using residue mulches, which can increase crop production, and the reduction of soil tillage and construction of water harvesting and supplementary irrigation system. Not only does it generate immediate benefits in terms of increased farm productivity, it also offers social benefits of great relevance to YRB.

Key words: Yellow River Basin; Rainfed field; Farming systems; Conservation agriculture

Yellow River Basin (YRB) is the birthplace of Chinese civilization and situated in Central China, between latitudes 32°-42°N and longitudes 96°-119°E. It originates in the connection between Qinghai and Sichuan Provinces and flows through Gansu, Ningxia, and Inner Mongolia and along the boundaries of Shanxi and Shaanxi and finally through Henan and Shandong before it empties itself into the Baohai Sea.

The Basin has a fairly rugged topography with the elevation decreasing from west to east (Fig. 1). Approximately 75% of the basin is covered with mountains and hills, while plain areas account for 17% only. Now, soil erosion, poverty and water shortage are major problems that affect the development of agriculture in YRB. These processes are particularly prevalent in sloping drylands which are the principal location of rainfed agriculture. According to the severe poverty and poverty lines (Wong Shiyou and Wang Biqiang, 2008), it is estimated that poverty incidence is over 20% in YRB. Agriculture is generally the main source of income for households in this region, therefore, increasing agricultural system productivity and improving the farmer livelihoods, are needed urgently.

The paper reviews the research and application of conservation agriculture in YRB and discusses the problem associated with conservation agriculture and their promising of adaptation in the future.

2. The Resource Base

2.1 Climate

In general, most of YRB is warm temperate zone monsoon climate. It has a high spatial pattern on temperature. In the upstream, the annual average temperature is 10~12~, and in middle stream, the value is 12.0~15.0~, and in downstream, the value is over 14.0" (Fig. 2. Left). The annual averaged precipitation is 452 mm. and it is spatially distributed 372 mm in the upper reaches, 523 mm in the middle reaches, and 671 mm in the lower reaches (Hong et al., 2002). From northwest to southeast, the rainfall increased gradually (Fig.2, Right) (Shao Xiaomei and Yan Changrong, 2006a).

Totally, annual average temperature is reducing gradually from the south to the north and from the east to the west in YRB. The average monthly temperature ranges from -8~29" with January being the coldest month and July the hottest month. Figure 2 shows that it has a trend for cumulated temperature of >0" and >10" downing from south to north or east to west (Liuqin and Yan Changrong, 2008).

Figure 3. The map of cumulated temperature >0" (Left) and >10" (Right) in YRB

The dryness index and annual water deficit can reflect the states of climate, Using the formula k = et 0 /p , K value was calculated for in the 100 weather stations. The average annual K value is 1.78, and in most of the basin, the value range 1~3.5 (Fig. 4, Left). The annual water deficit has similar spatial distribution, and value range is -110.8~871.5mm (Shi Jianguo and Yan Changrong, 2008) (Fig. 4, Right).

2.2 Soil and Water Resource

Soil is a product of integrated affected by natural factors, such as topography, landform, climate, and human activities, such as tillage. Due to the spatiality of natural factors in YRB, from southeast to northwest, the soil types are

Figure 4. Spatial pattern of annual dryness index and water deficit of 45 years in YRB

drab soil, brown soil, castanozem, gray cinnamon soil, dark loessial soil, cumulic cinnamon soil, loessal soil and desert caliche soil. Drab soil, castanozem, dark loessial soil, cumulic cinnamon soil, and loessal soil are mainly for agricultural production.

According to the data of Ministry of Land and Resource, arable land of 9 provinces in YRB are showed in following table, which indicates that the irrigable land and rainfed land are the main type of arable land, 33.54% and 62.31% respectively, and the other 3 types of field amount to a limited area.

Figure 5. Map of soil type in YRB

YRB is located in arid and semiarid region with shortage of water resource, annual average runoff is 58 billion m3" about 2% of total annual runoff in China. Water resource of per capita and per arable land hectare are 593 and 4860 m3 respectively, which are 25% and 17% of average value of China. It has very different spatial pattern of water resource, for example, in upper reaches, about 30% of the basin area, the runoff is over 58% of total amount. According to the rainfall, it can be divided 3 type of rainfall years, wet year, normal year and dry year, and the runoff of wet year is 3 times of dry year. So, water shortage and uneven is main characteristics.

Talbe 1. The arable land area of provinces in YRB (ha)

Province Counties Counties Irrigated Rainfed Irrigable Rainfed Vegetable

in YRB paddy paddy field field field

Shanxi 119 82 10532 78 868036 3182794 20122

Inner Mongolia 118 30 81108 350 1714240 5257295 47761

Shandong 139 30 129936 813 4340853 2872376 174943

Henan 158 46 645782 50699 3092552 4055085 81186

Shaanxi 107 74 172924 22913 870038 3005516 17786

Gansu 86 54 11261 2435 1003595 3642442 7996

Qinghai 43 33 0 0 176537 357328 8380

Ningxia 23 19 44845 0 353049 698820 3168

Total 793 368 1096388 77288 12418900 23071656 361342

Note: 2005 data from Ministry of Land and Resource, P. R. China. 6 counties in Sichuan are not included in the table, because very little arable land in these counties.

2.4 Farming Systems

In YRB, the main crops are wheat, maize, millet, potato, rape and cotton. The main farming systems are one crop per year, three crops two years and two crops per year, and the cropping systems largely depend on climate. According to features of farming systems, there are 6 first-level crop plantation types and 15 second-level crop plantation systems in YRB (Fig. 5). In the upper region of YRB, where involves transitional ecotone of agriculture and pasture, including the regions between Xining and Lanzhou, Ningxia and Inner Mongolia, the cropping system is one crop per year, such as maize, wheat or oat etc.. In middle region, such as north part of Wei River basin and valley area of Wei-Fen River basin, due to plenty water resource and solar radiation, main crop system is three crops two years, such as spring maize-winter wheat-summer soybean, spring maize-winter wheat-summer potato, winter wheat-summer soybean-winter wheat-summer fallow, winter wheat-winter wheat-summer maize. In the irrigated region of lower region of YRB, such as southeastern plain of Shandong and Henan, the main cropping pattern comprises two crops per year, such as summer maize-winter wheat, summer maize-vegetable (garlic), summer cotton-winter wheat (Fig.5) (Liu Xunhao, 2005). Correspondingly, the cropping index in the south plain of Shandong, Henan and part of Shaanxi, which has fertile soil and abundant water resource, can be as high as 140~170%. Conversely, in the cold dry north of Inner Mongolia, part of Shaanxi and Shanxi Province, the multiple cropping index tends to be below 80%.

Figure 5. The divisions map of farming system in YRB

3. Problems Encountered with Conventional Tillage System

Soil erosion is a severe problem in this basin, and most of the sediment originates in the thick loess deposits of Shaanxi and Shanxi Provinces. However, soil erosion, both by wind and water, in the basin as a whole removes the most fertile topsoil and aggravates the critical Basin-wide water shortages for agricultural, industrial and domestic purposes and air pollution problems. Only a decade ago demand for fresh water exceeded supply to the extent that the river low dropped to catastrophically low levels. These processes are particularly marked in the drier and more sloping lands associated with dryland agriculture. As conventional tillage, the intensification of crop production results in the environmental problem more serious, especially during the fallow period, and it is easy to wind or water erosion for unprotected and plough soil, leads to land salinity and infertility, and construct tillage pan (Tang, 2002; Wang, 2007). Conventional tillage and crop production practices have also led to a decline of soil quality in many parts of the Basin (He Wenqing and Yan Changrong et al 2008).

How to manage and utilize the crop residues is one of the greatest challenges for conventional tillage as well as, in a different way, conservation agriculture (Sayre and Dixon 2006).. The amount of crop residue is over 600 million tons per year, most of which is discarded or burned in the field. During recent year, residue burning has resulted in a lot of environmental problems, such as air pollution, breaking smoothly traveling of high way and normal activities in airport. Every year, in harvesting time of wheat and corn, the government had to invest much effort to prevent residue burning.

It is widely recognized that CA, is the most promising crop production approach from the perspective of sustainability (Sayre K, 2006). Through the principles of minimum soil movement, retention of residues, effective rotations and immediate economic benefits to farmers, CA addresses the problems of the YRB described above; and shows signs of becoming the next global agricultural revolution.

4. CA Technology Development

4.1 Evolution of CA Technology

In YRB, because water shortage and drought occurs frequently, local farmers have developed some methods to alleviate the effects of drought on agricultural production. The traditional methods include mulching, reduced tillage and no tillage, which are known well as55 sandy covering cultivation', 'furrow-seeding or square-pit methods'. The area is well known for intensive tillage dating from the traditional agriculture two thousand years ago in China. As the cradle of Chinese civilization, the basic characteristics of agriculture production are aligned with high input, especially labor intensive, practices. In the dry land area of YRB, the traditional agricultural production system includes plowing, harrowing, smoothing, rolling and hoeing. With the development and progress of agricultural science input use efficiency has been improved gradually, especially after the 1980s. The environmental problems, such as soil and water erosion, soil compaction, ground water table decrease and erosion of river banks are closely related to agricultural activities, leading to the study and improvement of the traditional tillage techniques and the possibilities offered by modern practices such as CA. Because of different climate, soil, landform, farming system, level of economic development, the experience with the development and impact of CA varies widely across the YRB.

As noted above, in the southern part of Loess Plateau in part of Henan, Shaanxi and Shanxi Province, double cropping of winter wheat-summer maize is common. In Gansu, Ningxia, Inner Mongolia and Qinghai, Shanxi and Shaanxi Province, single cropping of winter wheat or summer maize is common.

For water and soil conservation, a new dryland CA practice is being tested, comprising reduced or zero-tillage with retention of stubble and mulching with straw. Over 10cm of wheat stubble is left in the field after harvest and 8-10 t/ha of wheat straw provides soil cover during the fallow period (Fig. 6). Sometimes, the stubble and straw are pushed down with a stone roller. When sowing date is approaching, the wheat straw mulch is raked into heaps in the furrow and 3~4 t organic fertilizer per hectare is applied. In combination with sowing, 300kg/ha ammonium and 300kg/ha urea are applied. After sowing, the wheat straw is spread in the field again. After 3~4 years, sub-soiling or a single deep tilling is conducted for improving soil compaction and breaking the tillage pan (Wang Zhaohua and Li Like, 2001) .

In the upper region of YRB, especially the ecotone of agriculture and pasture such as Inner Mongolia, northwest of Gansu and south part of Ningxia, main cropping system is one crop per year, such as wheat, maize, potato and oat. For large scale, the key CA technology is reduced tillage and strip intercropping system (Fig. 7), which key function of

Figure 6. Reduced tillage with stubble mulched in Shaanxi Figure 7. Belt intercropping system in Inner Mongolia

this planting system is to reduce soil erosion, including wind and water erosion. This strip intercropping system involves: in late fall, after harvesting oat and potato, no-till and retaining oat stubble in the field (3.6~8.4m); next spring, and oats is directly sown in the former potato strip, and potato is planted in the former oat belt and the reverse the following year (Wang Shimin, 2004; Jia Yanmin, 2004).

In Ningxia and Gansu Provinces, an absolutely different CA technique-stone mulching, is used. In general, the field is mulched with stone (about 3~5cm diameter, about 10cm depth) which lasts for 10 years. Farmers plant cash crops such as melon and vegetables in these fields (Fig. 8).

The food bowl of the lower reaches in YRB is the Huanghuaihai plain in Henan and Shandong Provinces, the main cropping system is two crops per year, winter wheat-summer maize, with the development of CA machinery and CA subsidy from government, no-till and direct seed techniques for maize is utilized broadly, which processing is after harvesting wheat with machine, about 15cm standing stubble in the field and 1/3 wheat straw chopped broadcasting in the field at same time, and then direct seeding and fertilizing with no till seeder.

In east part of Shanxi Province and west part of Henan of YRB, for dryland, one crop per year is common, and crops include spring maize, oat, millet and potato. One CA practice is chopping straw and returning to field during maize harvesting, followed in the spring by concurrent seeding and fertilizing. Just now, in Shanxi, one third of maize planted area is adopted straw returning to field (Fig. 9).

Figure 8. Scenarios of melon field with stone Figure 9. Maize harvesting and straw chopping and

mulched in Gansu returning in Shanxi

Although the basic elements of conservation agricultural techniques were developed and practiced many years ago, in fact research on CA in YRB began during at the late 1970s. Some agronomists began to evaluate reduced tillage and no tillage in YRB and designed water and soil conservation till system for Loess Plateau region, including mulching with whole corn straw retained on dry land. The first no till seeder was made during this period (GAO

Huanwen, 2004). Around the end of the 1980s, the techniques of residue mulching and reduced till, leaving of high stubble after harvest and reduced till for wheat planting were assessed and applied (Li Shaokun, 2004y%-X?%-Zhang Fei, 2004). During the 1990ss for drought resistance and reducing soil erosion, an integrated conservation agricultural system with improved machinery was tested and promoted. During these decades much was learnt about CA practices with potential in the YRB but the adoption by farmers was very limited, and CA trails conducted only in 4 agricultural stations belonged to national or provincial agricultural academy.

In the first decade of this new Century, in the east part of YRB, zero tillage with residue incorporated for maize has been adopted significantly on irrigated areas of Henan, Shandong and Shanxi province, and the area utilized reduced till arrived several million Chinese mu. Most research results have shown zero or reduced tillage with residue kept in the field can decrease soil erosion in dryland fields and increase the soil water availability. In the northwest part of YRB, some CA technique, such as strip cropping, intercropping contour planting and strip tillage have also been applied to control soil erosion (Yan Changrong, 2006, Xin Naiquan, 2002).

4.2 Critical Research Results

The CPWF Project for the development of CA in the YRB has been operating research and demonstration trials in five representative locations across the YRB since 2005. The research is focused on critical questions on soil quality, moisture management, agronomy and crop productivity related the problems described above. The following tables compare average soil moisture of conventional tilled research plots and CA plots in five locations across the YRB. And the data indicate CA techniques can increase soil moisture and lessen water stress on crop growth, although the effects of CA on soil moisture depend on many factors, including the tillage, mulching and so on.

The increase in average soil moisture through the growing period is evident, ranging from 1% to 20% (Table 2). As in many other farming systems in the world, CA did not significantly increase crop yields. However, as reported in table 3, the improved soil moisture management contributes to an improvement of soil moisture and increase crop yield (Table 3). However, because of reduced production costs there is a fundamental increase in profitability of CA. For example, as shown in table 4, the results of Shouyang pilot site in Shanxi Province, CA is associated with the reduction of crop production inputs, such as labor, machine. With CA tillage the total inputs may decrease 15~20%. This is consistent with farmer perceptions of the advantages of CA component technologies which are primarily centered on saving labor, and the net income of CA can increase 5.8%~8.3%.

5. Government Support to CA

In recently years, Chinese government adopted a series of policy, economic measures to push CA techniques extension in YRB. MOA has set up 59 CA demonstration counties to extent CA techniques in the basin since 2002 (Table 5). With significant subsidy for CA machinery and effective CA training, it is estimated about 50,000 Chinese mu (approx 3,300 ha) of CA was adopted on arable land per CA demonstration county per year. In general, with development of new CA machinery, more clean understanding advantage of CA, the application of CA will extent quickly, especially for main crops, such as summer maize and winter wheat. With the government support, the capacity of CA application

Table 2. Soil moisture CA/Conventional, five sites

Pilot Soil depth (cm) Soil moisture increased (%) Note

Shandong 00~20 2.0~9.3 From 2008 annual report of Shandong site (the data is measured in March to

20~40 1.2~2.0 May, crop is winter wheat, Wang Fahong, 2008)

Henan 0-200 3.0~8.0 From 2008 annual report of Henan site (the data is measured during the growth period of winter wheat, Zheng Fei, 2008)

Shanxi 0-40 5.2~15.0 From 2007 annual report of Shanxi site (the data is measured during the growth

40-200 1.0~5.0 period of summer maize, Yan Changrong, 2008)

Inner Mongolia 3.0~15.0 From 2008 annual report of Inner Mongolia site (the data is measured during the growth period of summer maize, Liu Jinghui, 2008)

Ningxia 0~20 Over 20 From 2008 annual report of Ningxia site (the data is measured during the growth period of winter wheat, Yuan Hanming, 2008)

Table 3. Crop yield of maize and winter wheat for CA vs. Conventional tillage in five sites (kg/ha)

Pilot Annual Winter wheat Maize Note

Rainfall CA CK CA CK

Shandong 611 3995 3339 6060 6075 From 2008 annual report of Shandong site (Wang

Fahong, 2008)

Henan 650 2600 2476 5838 5652 From 2008 annual report of Henan site

(Zheng Fei, 2008)

Shanxi 47G - - 7030 6900 From 2007 annual report of Shanxi site,

(Yan Changrong, 2008)

Inner Mongolia 41G - - 4838 3890 From 2008 annual report of Inner Mongolia site

(Liu Jinghui, 2008)

Ningxia 4GG - - 5823 4723 From 2008 annual report of Ningxia site (Yuan Hanming,

2008.) (CA +mulching with plastic film)

Note: in Shandong and Henan pilots, cropping system is two crops per year, and in another 3 pilots cropping system is one crop per year.

Table 4. The input and outcome of different tillage for maize in Shouyang County (2008) (Yuan/ha)

Treatment _Input__Income__(%)

Fertilizer Machine Seed Pesticide Labor Total Gross Net

CK 1500 1125 412.5 150 1650 4838 11730 6892

CA ASRT 1500 1125 412.5 150 1500 4688 12149 7461 8.3

NTSM 1500 300 412.5 150 1500 3863 11305 7442 8.0

RRT 1500 525 412.5 150 1500 4088 11380 7492 5.8

Average 1500 650 412.5 150 1500 4213 11611 7398 7.3

Note: CK-All stalk is moved away, and plowing in autumn, and harrowing and seeding in spring; ASRT-Whole stalk ploughed into 0~20cm soil layer in autumn, seeding and fertilizing in spring at one time; NTSM-whole stalk were covered on field surface, and no till and directly seeding in next spring;

RRT-About 1/3 straw is chapping and rotary ploughed into 0~15cm layer in autumn, and in next spring, harrowing and seeding.

Table б. CA pilot counties in YRB during 2002-2007

Province County Name Pilot Total

counties counties

Shanxi Zuoyun, Pianguan, Shouyang, Changzi, Xiaoyi, Tunliu, Xiyang, Xiangfen 8 82

Inner Mongolia Liangcheng, Wuchuan, Yijinhuoluoqi, Dongsheng, Guyang, Chayouzhongqi, Qingshuhe 7 29

Shaanxi Shenmu, Dingbian, Tongchuan, Pucheng, Heyang, Binxian, Fuping, Henshan, Longxian, 15 74

Jingbian, Huangling, Hancheng, QIanxian, Qianyang, Chengcheng

Gansu Xifeng, Gangu, Yuzhong, Jingchuan, Ningxian, Lingtai 6 51

Ningxia Pingluo, Lingwu, Yanchi, Zhongwei Pengyang* 5 19

Qinghai Huangzhong, Xinghai, Huzhu, Datong, Pingan, Huangyuan 6 32

Henan Yanshi, Puyang, Huaxian, Boai, Junxian, Wushe, Luolong, Xiuwu 8 47

Shandong Huiming, Zhangqiu, Gaoqing, Yanggu 4 30

Total 59 3б4

has improved greatly, which include farmer's understanding of CA and agricultural implements. The percentage of agricultural production activities with machine increased sharply. For example, in Shanxi, Shandong and Henan, over 80% area of planting maize mainly depend on no till seeder. In Inner Mongolia and Ningxia, small CA seeders suitable for mountain or hilly region, are developed and applied broadly in recent year.

6. Conclusion

More suitable and better CA techniques for dry land in YRB are being developing by introducing new soil and water management techniques, new machinery and improving the traditional drought resistance practices (Reicosky, 2007; Xu Jiguang, 2005). The CA techniques have showed very good results in the research and demonstration sites.

Compared to conventional tillage system, CA tillage system can improve rainwater harvesting and water efficiency, increase water storage, reduce soil erosion, save energy and labor input (Table 4). The crop yields utilizing CA techniques are not much different compared to conventional tillage. In wet years, CA techniques maybe induce low soil temperature and seed emergence in part of YRB and decrease crop yield, and in normal and dry year, crop yield may be increased lightly. But farmer's net income from crop planting can increase obviously with utilization of CA techniques. In a word, CA is the most promising sustainable agriculture option for us. Not only does it generate benefits in terms of improved water use efficiency, increased farm productivity, but also offers social benefits of relevance to YRB.

Acknowledgement

This study was funded by a grant from the CGIAR Challenge Program on Water and Food (CPWF) "PN12: Conservation Agriculture in Yellow River Basin dry lands", and the 11th five-year plan of National Key Technologies R&D Program: "Water Balance and Crop Potential Productivity in Field Scale (No. 2006BAD29B01)", the 11th five-year plan of National High-tech R&D Program: "The Pilot Base Construction of Modern Water Saving Technology of Agriculture in Shanxi Province (No.2006AA100220)".

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Innovations through Conservation Agriculture: Progress and Prospects of Participatory Approach in the Indo-Gangetic Plains

M.L. Jat1, Ravi G. Singh2, Y.S. Saharawat3' 4, M.K. Gathala4, V. Kumar4, H.S. Sidhu5, and Raj Gupta2

1 Directorate of Maize Research, Indian Council of Agricultural Research, Pusa Campus, New Delhi, 110 012,

2International Maize and Wheat Improvement Centre (CIMMYT), India Office, NASC Complex, Pusa, New Delhi, 110 012, India 3International Centre for Soil Fertility and Agricultural Development (IFDC), Muscle Shoals, Alabama, USA 4International Rice Research Institute (IRRI) India Office, Pusa New Delhi, 110 012, India 5Punjab Agricultural University, Ludhiana, Punjab, India

The scientific and technological innovations have been the basis for promoting agricultural development. The historical focus of research on improved agricultural technologies has undeniably been successful. But, these strategies have had limited impacts on the intended beneficiaries, as the complexity of their livelihood and farming systems has not been taken in to consideration. The conservation agriculture (CA) in its initial version of zero-tillage in South Asia during 1970's and 80's is a good example of it wherein during technology development, little or no attention was paid to the farmers' knowledge for their local settings and innovations. However, linking dynamic knowledge systems of the farmers with scientific basis of technology through "Participatory Innovation Development" on CA in its version of Resource Conserving Technologies (RCTs) played a great role in promoting the adoption of RCTs (3.0 million hectares) for resource conservation, poverty alleviation and sustainable development in irrigated intensive production systems of the Indo-Gangetic Plains of South Asia.

The Indo-Gangetic Plains (IGP) of South Asia encompassing most of northern and eastern India, the most populous parts of Pakistan, terai of Nepal and virtually all of Bangladesh is a fertile and most productive region that supports 1/7th (900 million) population of the world. In the IGP, rice and wheat are the major crops grown in rotation on 13.5 m ha area. In addition, the other major crops grown in system are maize, sugarcane, and cotton. The rice-wheat (RW) production system has played a vital role in food security and remained the cornerstone for food security, rural development and natural resource conservation in the region (Paroda et al, 1994; Timsina and Connor, 2001; Gupta et al, 2003; Ladha et al, 2003). But, now evidences of second generation problems such as declining factor productivity, plateauing crop productivity, declining soil organic matter (SOM) receding ground water table, diminishing farm profitability, environmental pollution etc. started appearing mainly attributed to monoculture of intensive conventional production systems (Sharma and De Datta, 1985; Hobbs and Gupta, 2000; Sharma et al, 2003; Gupta and Sayre, 2007). At present, the challenge is to produce more quality food from the same land and water resources, besides sustaining soil and environmental quality. Thus, the major challenge for the researchers is to develop an alternative system that produce more at less cost and improve farm profitability and sustainability (Gupta and Seth, 2007). This suggests that agriculture systems needs a mixture of new technologies that are able to knock new sources of productivity growth and are more sustainable. This necessitates more attention on issues of sustainability and conservation agriculture (CA) in intensive production systems. The CA in its initial version of zero tillage before 1990's could not make much impact at farm level despite of the proven advantages of higher crop productivity, resource conservation and improving farm profitability because of higher investment costs of the imported ZT drills and design problems associated to suit the location-specific adjustments of the local ZT drills. The research efforts made since mid 1990's on developing, refining and accelerating the adoption of CA technologies in the IGP has brought a "Tillage Revolution" in which the 'Farmers Participatory Research Approach' played significant role. In this paper, progress and prospects of technologies involving one or more of the key elements of CA in the predominant cropping systems (rice-wheat, maize-wheat, rice-maize and sugarcane based systems) developed, evaluated and accelerated in various agro-ecologies of the IGP using innovative modifications in the planters and/or other production techniques through farmer's participatory research approach are being discussed.

Development, Evaluation and Acceleration of Innovative CA Techniques

Research on CA in irrigated production systems of South Asia in its version of zero tillage can be traced back in 1970's wherein efforts were made to develop the zero tillage technology at Punjab Agricultural University, Ludhiana, India. However, the technology did not reach at farm level due to the obvious reasons of lack of innovations for

location/situation-specific suitability. In early 1980s, the CIMMYT made efforts on zero-till technology in the region with the import of Aitcheson zero till drills from New Zealand to Pakistan. After Pakistan, four drills were shipped from New Zealand to India by CIMMYT during 1988, however, due to expensiveness of the imported ZT drills and poor crop establishments due to design problems in the locally manufactured ZT drills, the technology could not made impact at farm level. Thereafter, the innovations started with use of "Inverted T" openers of Aitcheson ZT drills in locally manufactured ZT drills in 1992. Thereafter, with the farmers' innovative suggestions for ZT technology, a series of improvements were made to make the technology user-friendly and acceptable at farm level. Later the commissioning of Rice-Wheat Consortium, an eco-regional initiative of CGIAR involving NARS of India, Pakistan, Bangladesh and Nepal in 1994, took initiatives in close collaboration of NARS of participating countries, manufacturers and local artisans for development and refinement of RCTs using "Participatory Innovation Development (PID)" approach. This PID approach made significant impact on resource conservation and sustainable farming through development, refinement and adoption of CA in its version of RCTs (3.2 million hectares) in the irrigated intensive production systems of IGP of South Asia (Table 1). Table 1. Adoption of RCTs in Indo-Gangetic plains of south Asia

Country/Region _Acreage under RCTs (000' hectares)_

2001-02 2002-03 2003-04 2004-05 2005-06

India 133.6 375.8 870.2 1870.5 2388.7

Pakistan 79.9 192.1 338.9 438.0 421.2

Bangladesh 10.4 10.4 10.6 388.8 419.9

Nepal 0.4 0.6 2.7 12.4 14.3

IGP 224.2 579.0 1222.0 2709.0 3244.0

Source: Gupta and Sayre (2007)

Farmer Participatory Field Trials

Results of large number of farmer's participatory on-farm and on-station trials across the IGP showed that no-till wheat in the RW system has shown similar system productivity as of conventional till wheat in rotation with puddled transplanted rice but with less water use and more farm profitability (US $ 50 to 100 ha-1) in western through eastern IGP (RWC, 2006). However, there was no much advantage on soil quality due to intensive tillage during rice season and no retention of residues. Further, the innovations of second generation planters (Happy seeder, turbo seeder, rotary disc drill etc) enabled to retain rational amount of residues in no-till systems that led to 6 to 20 % increase in system productivity, 50-100 mm saving of irrigation water, higher farm profitability (US $ 95 to 190 ha-1), enabled regulating terminal temperature up to 2 oC in wheat (Figure 1), reduced global warming potential (GWP) and improved soil quality. The benefits in respect to water saving, profitability and soil health in the RW system further improved with development of double no-till technology wherein rice was directly sown using innovative precise (cupping type, inclined plate) seed metering systems. Double no-till practice (no-till direct-seeded rice-No-till wheat) having rational soil cover with residues led to higher (US $ 200 to 240 ha-1) profitability of RW system compared to puddle transplanted rice-no-till wheat across the IGP (Table 2). In maize-wheat (MW) rotation, permanent beds (PB) and double no-till using disc openers and inclined plate multi-crop precision seed metering systems resulted in higher systems' grain and water productivity than the conventional practice. The profitability of MW system (average of 3 yrs) under PB and no-till (US$ 863-865 ha-1) was similar but higher than conventional till (US$ 543 ha-1) and had positive effect on soil health (Jat et al 2008a). In rice-maize (RM) rotation in the eastern IGP, double no-till resulted in 17% increase in RM system productivity compared to conventional tillage. The PB system improved the RM system productivity by 5% when residues were not retained and to 18% when residues were retained over conventional till practice (Figure 2). Similar to cereal production systems, innovative new generation planters also increased the sugarcane productivity by 21-58% (Table 3) and farm income by US$ 250 to 300 ha-1 compared to conventional planting techniques in sugarcane based system through advancing cane planting in furrows and wheat or other winter crops on top of the raised beds. In this production system, the disc planters enabled planting of winter crops as intercrops with cane ratoon having thick cane trash that could increase the farm profitability by 15-20%. Also the development of innovative bullock drawn and modular power tiller operated ZT planters have made significant impact on small and marginal farmers, and Hill agriculture where mechanization is very difficult.

The laser assisted precision land leveling, a precursor technology for RCTs was introduced for the first time in India at farm level in western Uttar Pradesh during 2001 that has been demonstrated and accelerated in larger domain in the region. Farmer participatory field trials were carried out on direct seeded (DSR) and puddle transplanted

< -7.5 Figure 1

No-till with and without surface retained residues effects on canopy temperature in wheat (ML Jat et al, 2008, Unpublished)

Table 2. Double no-till effects on yield, water productivity and profitability of RW system

Tillage Systems RW System Yield (t/ha) RW System Input Water Use (cm) RW System Net Returns (US$/ha)

TRR-ZTW 11.9 a 316.7 887 d

ZTDSR-ZTW+Residues 11.5 a 306.8 1128 a

ZTDSR-ZTW 11.1 b 304.9 1073 b

RTDSR-ZTW+Residues 11.9 a 308.6 1086 ab

RTDSR-ZTW 11.4 a 306.3 1013 c

Average 11.6 a 308.7 1037 bc

TPR- Puddled transplanted rice, ZTDSR-Zero till direct seeded rice, RTDSR- Reduced till direct seeded rice, ZTW- Zero till wheat Source: ML Jat et al (2008), Unpublished

J J J J

/Ill/mill HftLjfa.-.'i- IWW i.ïiHjfciu]51c-

ZTR-Zero till rice, ZTM-Zero till maize, PBR-Rice on permanent beds, PBM-Maize on permanent beds Figure 2. Conventional v/s conservation tillage in rice-maize, an emerging cropping system (Singh Ravi Gopal et al, 2008, Unpublished)

rice (TPR) during 2005 and 2006 revealed that the yields of both DSR and TPR increased with laser land leveling compared to traditional land leveling during both the years. The average yield of rice with laser land leveling was 6 and 12% higher compared to traditional land leveling practices during yr 1 and yr 2, respectively (Table 4). The average water saving in rice under laser leveling compared to traditional leveling was recorded at 9.5 and 6.6 % respectively during 2005 and 2006. Further, it was recorded that the water saving due to laser leveling compared to

Table 3. Yield of wheat and cane under innovative (FIRB) and conventional planting systems, western IGP, India

Crop establishment techniques _Western Uttar Pradesh_ _Haryana¥_

_Year-1a Year-2b

Wheat Cane Wheat Cane Wheat Cane

yield yield yield yield yield yield

(t ha-1) (t ha-1) (t ha-1) (t ha-1) (t ha-1) (t ha-1)

FIRB planted wheat- summer planted sugarcane - - - - 6.00 60.0

(Sole cropping) (± 0.22) (± 7.10)

FIRB planted wheat-sugarcane intercropped in 3.44 81.8 4.21 78.9 5.84 94.5

furrows (simultaneous cropping) (± 0.34) (± 6.9) (± 0.22) (± 7.2) (± 0.25) (± 8.11)

Conventional flat planted wheat-summer planted 3.50 59.5 4.35 64.6 5.57 60.0

cane (sole cropping) (± 0.21) (± 7.2) (± 0.31) (± 8.1) (± 0.31) (± 7.78)

a11 farmer participatory field trials, b9 farmer participatory field trials, ¥7participatory field trials Source: Jat et al (2005)

traditional leveling was more in TPR being 1338 and 1271 m3 ha-1 respectively during yr1 and yr 2 compared to DSR with 1271 and 333 m3 ha-1. A marked improvement in water productivity of rice was recorded due to laser land leveling compared to traditional leveling irrespective of crop establishment techniques, however, in yr 1, the improvement was much more under DSR compared to TPR but in yr 2 it was similar under both the establishment techniques (Table 4).

Efforts are being made to accelerate the adoption of this technology as an entry point for the CA based RCTs for realizing the potential benefits of RCTs at farm level. Being an initial cost intensive technology, initial progress was very slow, but large scale demonstrations and promoting custom services has resulted in very fast progress during last three years and currently nearly 925 farmers are rendering custom services on laser technology in the Indo-Gangetic Plains of India (Jat et al 2008c) mainly concentrated in the western IGP (Figure 3). The adoption of laser leveling technology is accelerating at multiple rates and currently nearly 0.2 M ha area has been brought under this technology in the IGP and saved significant energy, irrigation water, fuel, and electricity in addition to the yield advantages in several crops and cropping system (Jat et al 2008c).

Table 4. Land leveling and crop establishment effects on rice grain yield, irrigation water use and productivity under farmer participatory field trials, Western Uttar Pradesh, India

Land leveling Crop Grain yield Irrigation water use Water productivity

establishment (t ha-1) (m3 ha-1) (kg grain m-3 water)

2005$ 2006# 2005$ 2006# 2005$ 2006#

Laser DSR 5.25 ab 4.90 a 11200 d 9067 d 0.50 a 0.54 a

TPR 5.41 a 4.94 a 13718 c 10150 ab 0.39 b 0.49 b

Traditional DSR 5.10 b 4.18 bc 12471 b 9400 c 0.41 b 0.45 b

TPR 4.98 bc 4.49 b 15056 a 11171 a 0.33 c 0.40 c

Mean 5.19 4.63 13111 9947 0.41 0.47

TPR- Puddled transplanted rice, DSR- Direct seeded rice, $17 participatory trials, #15 participatory trials Source: Jat et al (2008c)

Figure 3. Growth of laser leveler custom service providers in the Indo-Gangetic plains of India

Conclusions and Future Prospects

Development and fine tuning of CA techniques for different production systems in the region in a farmer participatory innovation development mode has made significant impact at farm level and accelerated the adoption of these CA based RCTs. Participatory research findings indicated that CA techniques has resulted in equal or higher productivity, savings in irrigation water use, improved farm profitability, reduced GWP, able to adapt with climate change effects, and improved soil health for long-term sustainable farming under intensive agro-ecosystems compared to conventional intensive tillage practices. However, for realizing potential benefits, the full CA involving all the key elements in systems' perspective are to be developed and adopted at farm level. Tailoring efficient genotypes for CA and tillage x genotype interaction studies in cropping systems perspective needs special attention in future. Long-term effects of CA on crop, soil, biodiversity and climate in various production systems and agro-ecologies should be the future agenda of research under natural resource management program. Animal component is the basis for farming and in CA, retention of crop residues is must, therefore, studies on conservation agriculture based farming systems should be initiated for long-term sustainability of the technology.

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Strategies to Overcome the Competition for Crop Residues in Southern Africa: Some Light at the End of the Tunnel

Patrick C. Wall

CIMMYT, P.O. Box MP163, Mount Pleasant, Harare, Zimbabwe (Email: p.wall@cgiar.org)

Most small-holder farmers in southern Africa rely on maize as their staple food and manage mixed crop/livestock systems where maize is the major crop and maize residues provide a vital source of livestock feed during the dry season when grazing areas are limited. Conservation agriculture on the other hand relies on ground cover with crop residues to achieve its potential to increase crop yields under rainfed conditions and increase soil health and system sustainability. The competition between the soil and animals for the scarce crop residues thus has become a major point for discussion and often disagreement. However, most analyses of total farm productivity during a transition to conservation agriculture from tillage-based agriculture assume that all of the farm will be converted to the new system in a relatively short period of time. This strategy, while conceptually simple, also results in the maximum competition for residues, and as a result tends to force a decision against CA before its promise of increased yields and system sustainability can be achieved. If the farm is converted gradually to CA, then competition is less, the farmer can learn to manage the new system properly under his/her conditions, and soil degradation on the farm can gradually be reverted while crop productivity increases. The reduced risk of crop failure with CA also allows diversification of crops on the farm, and may include the production of forage crops with markedly better nutritional quality than cereal crop residues. Using examples from farmer managed plots in southern Africa the paper will explore the effects on total productivity. However, there are other difficulties with surface residue retention, principally communal grazing rights after harvest and the prevalence of wild fires or bush fires. Both of these need to be taken into account and while the farmer can control aspects of the solution, overcoming the problems will involve important policy decisions at the community and district levels.

Key words: Crop Residues, Conservation Agriculture, Southern Africa

Conservation agriculture (CA) is a sustainable production system that is based on three principles: minimal soil movement, retention of crop residues on the soil surface and crop rotation. Other principles of productive crop systems also need to be followed such as the use of adapted varieties, replenishment of soil nutrients, good control of weeds, pests and diseases, and generally good crop husbandry and management. However, the three principles set CA apart from much of the world's agriculture which relies on intensive soil tillage, removal and/or burning of crop residues and often monoculture.

Relatively little of the 95 million hectares (Derpsch, 2008) of no-tillage agriculture worldwide, much of which would classify as CA, is managed by smallholder farmers. However, there are important areas of CA on small farms in Brazil, Paraguay, China, Ghana, Zambia and increasingly in Zimbabwe. While there is as much as 2 million ha of wheat sown without tillage in the rice-wheat system of the Indo-Gangetic Plains (www.rwc.cgiar.org), most farmers still intensively till the land for the rice crop.

The principles of CA are equally applicable to large and small farmers, but the techniques and technologies to put the principles into practice depend on farmer circumstances as well as the biophysical conditions. For instance, the equipment utilised in CA by large and small farmers is very different in scale and draught source. This system and circumstance specificity poses a considerable problem for traditional research and extension systems based on a linear flow of knowledge from research to extension to the farmer, as it is impossible for research to develop systems that are adapted to all circumstances. This has resulted in considerable agreement on the need for the development of innovation systems that incorporate multiple agents, including farmers themselves, in a network that focuses on developing systems that function on the fields of innovative farmers (Wall et al., 2002).

Functional CA systems provide multiple benefits to the farmer and the environment. The relative importance of these benefits depends on the most limiting components of the agricultural system, but includes both short-term benefits and others which accrue over time. Short term benefits include increased water infiltration, reduced evaporation, reduced surface crusting, reduced water run-off and soil erosion, and reduced labour demand and fuel use: together these may lead to increased productivity in the first seasons of application of the new system as well as important offfarm environmental benefits. Longer term benefits include: increased soil organic matter levels resulting in improved

nutrient use efficiency; improved soil biological activity which results in improved soil structure, aeration and drainage; increased crop productivity; and increased biological pest control. The incorporation of adequate crop rotations can also result in higher yields, reduced peaks of labour use, and reduced level and frequency of crop diseases.

Most of the benefits of CA result entirely or partially from surface residue cover: not only do the residues protect the surface soil from raindrops and radiation thereby reducing surface sealing, soil crusting and moisture evaporation, and increasing infiltration, but they provide a food source for the soil fauna and flora leading to the increase in soil biological activity that is one of the main drivers of increased system productivity, resilience and sustainability. Obviously, therefore, trying to manage no-tillage systems without surface residue cover will not result in the benefits that accrue to CA systems, and the yield of crops direct-seeded into bare soil is often considerably lower than that of crops sown with conventional tillage practices (Wall, 1999; Sayre et al., 2001).

Because of the importance of soil cover, successful establishment of the system is increasingly difficult in low productivity systems where enough crop residues cannot be produced to achieve adequate levels of ground cover for the following crop. Therefore no-input or low-input strategies are not compatible with CA: sufficient inputs need to be applied not only to achieve increased economic yield but also to produce sufficient residues for "adequate" ground cover for the future. The necessary amount of crop residues or the level of ground cover needed will no doubt be different under different circumstances, and is still a relevant question in many systems, including those semi-arid areas where the principal benefit from CA is generally improved crop water balance. For conditions where soil erosion by water is the major limitation, 30% of ground cover by residues is generally accepted as a target level given that in many studies it reduces soil erosion by at least 75% (Allmaras and Dowdy, 1985; Erenstein, 1997). This level of ground cover can be achieved with as little as 1 t ha-1 of maize residues, whereas 3 t ha-1 of maize stover gives approximately 50% ground cover and a 90% reduction in soil erosion (Erenstein, 1997).

However, smallholder farmers in developing countries generally manage intensive, mixed crop-livestock systems where animals are extremely important components of the system: they contribute to the food security of the household, provide for system diversification, generate cash, spread risk, recycle nutrients, provide draft power and transportation, and are important assets for investment and/or savings (de Haan et al., 1997). Crop residues are an important source of feed, albeit often of low nutritional quality, or of extra income: in South Asia a kilogram of straw is worth from 13 to 32% of a kilogram of grain (O. Erenstein, personal communication). Therefore the need to leave crop residues on the soil surface in CA systems implies direct competition for a scarce and/or valuable resource. As pressure on the land increases, more arable land is dedicated to crops, intensifying the interactions and conflicts between crops and animals (Mueller et al., 2001).

In more marginal environments, crop productivity is lower and therefore crop residues are scarcer and competition for them greater. In areas with prolonged dry seasons, the demand for residues for feed is the greatest (McDowell, 1988; Sandford, 1989; Quiroz et al., 1997). Thus in the irrigated areas of the Indo-Gangetic plains where production levels are high and two or more crops per year are feasible, competition for residues between the needs of soil conservation and livestock feed is less of a problem (Teufel et al., 2008) than in the drier environments of northern and southern Africa, west Asia and parts of the Andes. The adoption of CA in these marginal environments will only advance when it can be demonstrated to farmers that leaving at least part of the residues on the soil surface gives a greater benefit to system productivity than feeding these to animals. That these increases in total system productivity are possible is evident in the results of Sayre et al. (2001): after several years of CA practices in central Mexico, productivity had increased sufficiently that more residues could be removed from the system for animal feed than in the conventional system, while still leaving sufficient for soil cover. However, managing feed supplies over the transition period from conventional agriculture to an established CA system is a problem that several authors quote as a major limitation to the feasibility of CA for smallholder farmers.

The use of residues for animal feed also has a social component. In many regions, especially in rainfed areas, communal grazing rights apply after crop harvest. Thus an individual farmer does not have exclusive rights to the residues on his land, and attempts to conserve them can lead to violent confrontation. For example, in central Mexico, Tripp et al. (1993) report several cases where farmers fenced their fields to keep residues, only to have the residues deliberately burned by irate neighbors. This complex issue can only be resolved by community understanding and involvement in the issue of land degradation, which itself involves considerable investment in information sharing and knowledge development in rural communities.

Strategies

Gradual Conversion to CA

Most evaluations of the problem of feed in the transition from conventional to conservation agriculture assume that the farmer will, or needs to, convert the whole farm to CA at the same moment. This is not necessary, and in fact is not advisable as it is important that the farmer learns to manage the new system properly under his/her circumstances and conditions before converting the farm to CA: in South America it is recommended that the farmer start with only about 10% of the farm, learn to manage the system properly and then gradually incorporate the rest of the farm to CA (Derpsch, 2001).

In Table 1 field data from large-scale farmer-managed demonstration plots at two sites in southern Africa has been used to calculate the impact of converting 10% of the farm to CA on grain production on the farm and stover available for feed. An average farm size for the region of 3 ha (Mekuria and Siziba, 2008) has been assumed. The two sites represent the extremes of productivity levels in the 43 communities in which we are working in southern Africa: Zimuto has extremely sandy soils (93% sand) and relatively low rainfall (mean of 631mm yr-1) while Zidyana soils are generally sandy loams and annual rainfall is approximately 1200mm. Two strategies of use of the crop residues are considered: a) all residues are left on the land in CA and removed in the conventionally tilled part of the farm; and b) residue production above 3 t ha-1 is used for feed from the CA plots (this situation does not occur in Zimuto, Zimbabwe). In all cases there is a slight reduction in the feed available on the farm, but this is offset to some degree by extra grain production. In the harsh environment of Zimuto, grain yields under CA have increased over time relative to the conventionally tilled check, and so in the first season of CA the "break-even" value of the stover (the value of the stover relative to the grain that would economically offset the loss of feed) was only 6% of the value of the grain, whereas by the third year of CA on the field, the break-even value was over 50% of the value of the grain. There is little marketed stover in the communities in which we work in southern Africa, but assuming an average value of that in India, quoted earlier, of 20% of the farm gate price of grain, it would take until the third year of establishment of CA on part of the land before the increase in grain production offsets the reduction in the value of the stover available for feed. At the same time the costs of production of CA are slightly lower than the conventionally tilled fields, and the variable costs of the CA treatment analysed were US$10 ha-1 lower than the costs in the conventionally tilled treatment, largely due to the opportunity cost of the animals involved in the tillage operations. This saving in costs results in equal benefits even in the first year of conversion of 10% of the farm to CA, and increasing benefits in subsequent years.

In the more productive environment of Zidyana, Malawi, the break-even value of the stover to offset the extra grain production was very high in the first two seasons of CA, but was lower in the third season when yield levels were generally higher and total feed production was higher than in the other years. Thus in this year, feed availability would

Table 1. Differences in grain and stover (feed) production calculated for three years on a 3 ha. farm in two sites in southern Africa after conversion of 10% of the farm to conservation agriculture. Data calculated from farmer managed demonstration plots at the two sites 2004-2008

Zimuto, Zimbabwe Zidyana, Malawi

Strategy 1 a Strategy 2 b

Grain kg Feed kg Stover breakeven value Grain kg Feed kg Stover breakeven value Feed kg Stover breakeven value

Year 1 Conventional 3217 3450 9454 10136 10136

10% CA 3239 3105 9767 9123 9572

Difference 22 -345 0.06 313 -1014 0.31 -564 0.56

Year 2 Conventional 3621 3882 8413 9020 9020

10% CA 3677 3494 8679 8118 8406

Difference 56 -388 0.14 266 -902 0.30 -615 0.43

Year 3 Conventional 4432 4752 10957 11749 11749

10% CA 4711 4277 11038 10574 10935

Difference 279 -475 0.59 81 -1175 0.07 -813 0.10

a Strategy 1. All residues left on the field in CA.

bStrategy 2. Partial residue removal from CA plots. Remove residues above 3 t/ha

not be a limiting factor. An economic analysis of results at the Zidyana site shows that the Marginal Rate of Return of the extra investment (mostly due to the costs involved in the application of glyphosate herbicide) in the CA plots was an impressive 426%, largely because of a saving of 21.5 hours of labour per hectare. For this reason, and the fact that in reality farmers in the community own very few large ruminants, CA is spreading rapidly in Zidyana.

Diversification and Fodder Crop Production

Maize is the staple food in southern Africa and smallholder farmers tend to ensure their family food security before venturing into the production of cash crops. Because of the variability of annual rainfall and the frequency of mid-season droughts, farmers tend to define the area they will seed to maize based on the area they will need to provide for their family food needs in a drought year. The limited nutrients available (both in organic and inorganic fertilizers) also tend to be spread over this area. Although this strategy may be the best under conventional tillage in dry years, in a good season with adequate rainfall, farm families do not have the labour necessary to weed the area, crop nutrition is sub-optimal, and yield levels are often just as low as they are in poor rainfall seasons, adding to the riskiness of agriculture.

Although we do not yet have the data to model the best farm strategies, maize yields in all the communities in which we are working with national partners are higher under CA, even in dry seasons. Therefore the risk of economic losses and/or crop failure is reduced. This reduction in risk affects optimum economic fertilization levels: effectively the risk of moisture stress is reduced by CA and so the optimum economic level of fertilization is higher. This is important for the functionality of CA systems. Under conventional agriculture the optimum strategy for the use of scarce nutrient resources is to spread the available nutrients over the whole area that can be weeded (Tabo et al., 2006) because, due to the law of diminishing returns, the productivity of a low rate of fertilizer is higher than the productivity of the same amount of fertilizer applied to a smaller area. This fertilization strategy, often called microdosing, assumes that the effects of applied fertilizer are for the current season only. However, because of the importance of the residues for soil cover in CA, the fertilizer strategy needs to take into account residue production and therefore effects in future seasons. The optimum fertilization strategy under CA is to concentrate nutrients on a smaller area, taking advantage also of the reduced risk of crop loss or failure due to moisture stress under CA. This strategy has the added advantage of reducing the area that needs to be weeded, reducing the cost of labour required to keep the crop weed free: an extremely important aspect for southern African farmers where more than 60% of the labour required to produce a crop is invested in hand weeding (Ellis Jones et al., 1998).

The reduction in risk and labour use under CA, together with the concentration of the maize crop on a smaller area, permit diversification of the farming enterprise. This has been a feature of the adoption of CA on small farms in Paraguay (Sorrensen et al., 1998) and is likely in southern Africa as well. Diversification may involve using the labour freed up by CA for other enterprises, including education and off-farm employment, and/or using the land freed up by the greater productivity of the staple crop for other crops, including the production of fodder crops with far higher nutritive value than the cereal crop residues. This fodder production then replaces the crop residues that are left on the soil surface, and at the same time results in better animal nutrition. Quantification of some of the possibilities under this strategy is currently underway: there is evidence from legume green manure cover crop (gmcc) production that far more biomass and protein can be produced on a relatively small area than is produced though the residues of the maize crop.

Local Policies and Communal Grazing

Communal grazing rights after harvest is one of the major problems experienced by smallholder farmers in many parts of the world who want to maintain their residues on the soil surface. In some countries and regions, this leads to tensions between crop producers and livestock producers, where the latter feel that they have the right to the otherwise "useless" and therefore "free" crop residues. Under these circumstances, where society places no monetary value on the crop residues, it is exceptionally difficult for individual farmers to retain their crop residues on their own fields. Obviously to change these norms, or local policies, involves a change in mind-set or paradigm, which makes the lifting of the communal grazing rights a difficult and time-consuming process. In the Zimuto Communal Area described earlier, some farmers have decided to remove the residues from the field, store them to avoid grazing by roving animals, and then return them to the field at seeding time once animals in the community have to be confined or sent to more distant grazing areas. However, we believe that this strategy is unlikely to succeed because of the labour involved and because it reduces the efficiency of capture of the early rains. We believe that it will be more important to

change the way communities understand and view resource degradation, involving an understanding that crop residues are not an un-needed and free resource, but that they are vital to agricultural sustainability.

Although the change in attitudes about residues, land degradation and communal grazing will undoubtedly be slow and difficult, there are some emerging examples of success. Near the town of Karatu in northern Tanzania, one early adopter of CA convinced his neighbours of the benefits of the system and the importance of the crop residues as soil cover. This group of neighbouring farmers then decided to stable their animals and restrict free grazing of their lands, leading to a community where residues are retained on the soil surface year round (W. Mariki, personal communication). In another village near Karatu, free grazing of animals has been disallowed by the local council (B.Sims, personal communication) because they have seen the benefits of residue retention. Another example comes from the Shamva District of Zimbabwe where a local policy maker observed the benefits of residue retention on our CA Project demonstration plots and re-enacted forgotten regulations which permit farmers to deny access to their fields to grazing animals. This latter example is important in that it shows the need to include local policy makers in the CA innovation system.

Other possibilities for restricting communal grazing involve fencing, either with wooden, wire or live fences. In theory the idea of live fences that also provide nutritive fodder should combine well with CA. However, to date we have not found farmers very receptive to the idea of live fences because of the space they occupy, but we need to invest more time with partners in exploring this option. The cost of wire fencing is generally prohibitive to smallholder farmers, but where wooden or wire fences do exist we advise farmers to initiate CA in these areas so that grazing can be controlled.

Fire and Residues

Fire has been a part of the natural ecosystems in southern Africa throughout history largely die to lightning initiated fires. However, anthropogenic fire is also widely used in the region to regenerate natural pasture and to hunt wild animals, from small antelope to mice. Fire poses a threat to farmers who want to keep their crop residues, and as in the example of Mexico quoted earlier, needs community awareness and commitment, and the intervention of local policy to help change attitudes towards the importance of crop residues for the sustainability of agriculture and land degradation in general.

Conclusion

The success of Conservation Agriculture under many conditions depends on soil cover with crop residues, a resource often used by smallholder farmers for other ends, especially for animal feed. Overcoming the competition for crop residues will not be easy, especially in low-productivity rainfed environments such as southern Africa where competition tends to be most intense. Animals are generally very important components of smallholder farms where they provide sources of income and draught power, as well as serving as a savings repository. Livestock often may be more important than crops in the farming system, and so reductions in feed availability provoke serious system incompatibilities. However, there are several strategies proposed that can allow for residues to be retained on the land while limiting the impact on total farm productivity. These include:

• A gradual transition to CA on the farm so that the impact on total farm feed production is small, and strategies for increasing fodder production over time (below) can be utilised. CA should be initiated only on a small part of the farm (10%) and gradually incorporated into the farming system.

• Taking advantage of increasing crop productivity, and therefore both economic yield and residue production, a portion of the residues can be used for feed and the remainder left on the soil

• Using some of the land freed up for producing other crops by the increased productivity and reduced risk of production of the staple crop, some area can be dedicated to the production of more productive and nutritive fodder crops.

• Control of free grazing of residues by animals through changes in attitude towards degradation and natural resources, combined with local policies

• Agroforestry and live fences that provide sources of high quality feed.

Obviously overcoming competition for residues in systems that are very resource-constrained will not be easy. However, the alternative of continuing with crop residue removal, tillage, and land degradation is not sustainable, and I believe it is unethical to continue to propose short-term solutions to smallholder farmers that will eventually lead to

their, or their descendants, demise. The time for "silver bullets" has gone - we need to look at the principles on which

agriculture is based and realise that returning undigested organic matter to the soil is a key to sustainability.

References

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The Importance of Crop Residue Management in Maintaining Soil Quality in Zero Tillage Systems; A Comparison between Long-term Trials in Rainfed and Irrigated Wheat Systems

Nele Verhulst12, Bram Govaerts1*, Els Verachtert2, Fabian Kienle3, Agustin Limon-Ortega4,

Jozef Deckers2, Dirk Raes2, Ken D. Sayre1

11nternational Maize and Wheat Improvement Centre (CIMMYT), Mexico, D.F., Mexico 2Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200 E, 3001 Leuven, Belgium 3Colegio de Postgraduados, Km 36.5 Carr. México -Texcoco, CP 56230, Montecillo, Mexico 4INIFAP-CEVAMEX, AP10, Km 17.5 Carr. México-Lechería, CP 56230, Chapingo, Mexico (Corresponding author (Email: b.govaerts@cgiar.org)

CIMMYT is committed to improving livelihoods in developing countries by improving the productivity and profitability of farming systems while sustaining natural resources. This paper focuses on the influence of crop residue management on soil quality in zero till systems and includes results from two long-term trials established in the early 1990's in different agro-ecological systems in Mexico: (1) a low-input, semi-arid, rainfed system in the rainfed central highlands (2240 masl) with zero tillage on the flat and (2) a high-input, arid, irrigated system in the northwestern part of the country with zero tilled permanent raised beds. In both zero till systems, the (partial) retention of the crop residues was necessary to maintain soil quality. In the rainfed semi-arid zero tillage system, mean weight diameter obtained by dry sieving, aggregate stability, infiltration, soil moisture content, soil microbial biomass and nutrient status were lower with residue removal than with residue retention. In the irrigated permanent raised bed system, burning of all crop residues resulted in a degradation of soil structure, lower direct infiltration, irrigation efficiency, soil moisture content, soil microbial biomass, lower total N and greater soil sodicity as compared to retaining crop residue at the surface. Practices with partial retention of crop residue showed soil quality similar to practices with retention of all residues. The retention of at least part of the crop residue is essential for the sustainability of zero till systems, although it may be possible to remove part of the residue for other uses, especially in irrigated conditions where biomass production is high.

Key words: zero tillage, permanent raised bed planting, residue management, soil quality

Human efforts to produce ever-greater amounts of food leave their mark on our environment. Persistent use of conventional farming practices based on extensive tillage, and especially when combined with in situ burning of crop residues, have magnified soil erosion losses and the soil resource base has been steadily degraded (Montgomery, 2007). Nowadays, people have come to understand that agriculture should not only be high yielding, but also sustainable (Reynolds and Borlaug, 2006). Farmers concerned about the environmental sustainability of their crop production systems combined with ever-increasing production costs have begun to adopt and adapt improved management practices which lead towards the ultimate vision of sustainable conservation agriculture. Conservation agriculture addresses a concept of the complete agricultural system, combining three basic principles (1) reduction in tillage, (2) retention of adequate levels of crop residues and surface cover of the soil surface and (3) use of economically viable crop rotations. These conservation agriculture principles are applicable to a wide range of crop production systems. Obviously, specific and compatible management components will need to be identified through adaptive research with active farmer involvement for contrasting agro-climatic/production systems.

This paper includes results from two long-term trials operated by the International Maize and Wheat Improvement Centre (CIMMYT) in different agro-ecological systems in Mexico. The first experiment is located near El Batán, approximately 30 km northeast of Mexico City, in the subtropical highlands of Mexico. Rainfed cropping predominates in the area, with rainfall (350-800 mm) occurring during a four to six months summer period, followed by dry, frosty winters. The climate of El Batán makes it representative of many highland areas in the West Asia and North Africa region, the Southern Cone and Andean Highlands of South America, the central highlands of Ethiopia, the Mediterranean coastal plains of Turkey and the highlands of central Mexico. Each area has its specific conditions and problems, but some overall trends are recognisable. The tropical and subtropical highlands (central Mexico, Ethiopia, ...) have been densely populated and intensively cropped for centuries resulting in agricultural sustainability problems related to soil erosion and fertility decline (Scherr and Yadav, 1996). The agricultural system is under stress due to shrinking cultivated area per household, reduced fodder availability and land degradation (Aune et al., 2001). Rainfall is inadequate and

unpredictable, hence crop production is threatened by chronic soil moisture stress. Precipitation is usually intensive and short, leading to high runoff and temporal water logging. Cereal grain yields are low (<2 t ha-1). Moreover, fields are often weedy and crops are N deficient, soil structure is poor, and sheet and gully erosion are widespread (Nyssen et al., 2000, 2005).

The second experiment is located in the Yaqui Valley in the arid, northwestern part of Mexico. In the Yaqui Valley over the past 25 years, more than 95% of the region's farmers have switched from using flood irrigation on the flat to planting on raised beds (Aquino, 1998). One to four rows are planted on top of the bed, depending on the bed width and crop, with irrigation applied in the furrow. Farmers growing wheat on beds obtain 8% higher yields and save nearly 25% in production costs, compared with the flood irrigation systems (Aquino, 1998). Grain yields in the area exceed 6 t ha-1 and input levels are high, e.g. the average N rate for wheat is 275 kg N ha-1. Widespread burning of crop residues often accompanies tillage, although some residues are baled-off for fodder and incorporated during tillage (Sayre, 2004). Bed planting provides a natural opportunity to reduce compaction by confining traffic to the furrow bottoms. The next logical step to increase the sustainability of beds is to make them permanent, avoiding tillage (only reshaping the beds as needed) and retaining and distributing crop residues on the surface.

A simple operational definition of soil quality is given by Gregorich et al. (1994) as 'The degree of fitness of a soil for a specific use'. Within the framework of agricultural production, high soil quality equates to the ability of the soil to maintain high productivity without significant soil or environmental degradation. Evaluation of soil quality is based on physical, chemical and biological characteristics of the soil. Management factors that can modify soil quality include e.g. tillage and residue management systems, and sowing crop rotations (Karlen et al., 1997). This paper focuses on the influence of residue management on soil quality parameters in zero till systems. A comparison is made between conservation agriculture systems in two contrasting agro-ecological areas: (1) a low-input, semi-arid, rainfed system with zero tillage on the flat and (2) a high-input, arid, irrigated system with zero till permanent raised beds.

Materials and Methods

The Rainfed Long-term Trial in Central Mexico

The rainfed experiment is located in El Batán in the semiarid, subtropical highlands of Central Mexico (2240 m a.s.l.; 19.3°N, 98.5°W). The soil has good chemical and physical conditions for farming. The major limitations are periodical drought, periodical water excess and wind and water erosion. The mean annual temperature is 14°C (19902001) and the average annual rainfall is 600 mm y-1, with approximately 520 mm falling between May and October. Short, intense rain showers followed by dry spells typify the summer rainy season and the total yearly potential evapotranspiration of 1900 mm exceeds rainfall throughout the year. The El Batán experiment station has an average growing period of 152 days. The soil is a fine, mixed, thermic Cumulic Haplustoll (Soil Survey Staff, 2003) (Cumulic Phaeozem (IUSS Working Group WRB, 2006)). The experiment was started in 1991 as described in Fischer et al. (2002). Individual plots are 7.5 m by 22 m. Standard practices include the use of recommended crop cultivars, with maize planted at 60,000 plants ha-1 in 75 cm rows and wheat planted in 20 cm rows at 100 kg seed ha-1. Both crops are fertilized using urea at 120 kg N ha-1, with all N applied to wheat at the 1st node growth stage (broadcast) and to maize at the 5-6 leaf stage (surface-banded). Weed control is done using appropriate, available herbicides as needed and no disease or insect pest controls are utilized, except for seed treatments applied by commercial seed sources. Planting of both maize and wheat depends on the onset of summer rains but is usually done between June 5 and 15.

The experimental design consists of a randomized complete block with two replications. There are 32 treatments in all. The core set of 16 management practices was based on variation of (1) crop rotation (monocropping vs. a maize/ wheat rotation); (2) tillage (conventional vs. zero tillage); (3) residue management (retention vs. removal). A second set of treatments was established in 1996 and includes treatments with partial residue retention and planting on permanent raised beds. In this paper only treatments with zero tillage on the flat and crop rotation will be considered.

The Irrigated Long-term Trial in Northwestern Mexico

The experiment was initiated in 1992 near Ciudad Obregón, state of Sonora, Mexico (Lat. 27.33° N, Lon. 109.09° W, 38 masl). The mean annual temperature is 24.7 °C and average annual precipitation 384 mm, with 253.1 mm in a rainy season from June until August (1971-2000) (http://www.inegi.gob.mx). The soil is a coarse sandy clay, mixed montmorillonitic Chromic Haplotorrert (Vertisol Calcaric Chromic), low in organic matter (< 1%) and slightly alkaline (pH 7.7). A detailed description of plot management has been reported in Limon-Ortega et al. (2000). Wheat and maize

are irrigated and managed in an annual rotation: wheat as a winter crop planted in late November to early December and harvested in May, followed by maize as summer crop planted in June on the same whole plots and harvested in October. Both crops are planted on 0.75 m raised beds with wheat in two rows seeded 20 cm apart and maize in one row. Irrigation is applied in furrows. The experiment includes three replicates of each treatment in a randomized complete block design with a split plot treatment arrangement. Main plots consist of tillage-straw factors as follows: (1) CTB-straw incorporated: Conventionally tilled raised beds (conventional tillage with beds formed after each crop); wheat and maize residues are plowed under; (2) PB-strawburned: Permanent raised beds (zero tillage with continual reuse of existing beds, which are reformed as needed); residues of both wheat and maize are burned; (3) PB-straw removed: Permanent raised beds; residues of wheat and maize are removed by baling; (4) PB-straw partly removed: Permanent raised beds; maize residues are removed by baling and wheat straw is retained on the soil surface; (5) PB-straw retained: Permanent raised beds; maize and wheat residues are kept on the soil surface. Only the permanent raised bed treatments will be included in this paper.

Split plots during the winter comprise seven N fertilizer levels, but for this paper we chose a set of three N treatments (0, 150, and 300 kg N ha-1). Maize receives a uniform application of 150 kg N ha-1. The N fertilizer is applied as urea in the bottom of the furrow and incorporated through irrigation. Each year wheat and maize receive 45 kg P2O2 ha-1 banded in the furrow and incorporated through cultivation when reshaping beds.

Soil Quality Parameters

Aggregate size distribution and stability were determined during the 2006 growing season in El Batán as described in Govaerts et al. (2006) and in Ciudad Obregón as described in Limon-Ortega et al. (2006). Time-to-pond, the time it takes before water runs-out of a specific area in the field, was measured during the 2006 growing season in El Batán and during the 2007-2008 season in Ciudad Obregón as described in detail in Govaerts et al. (2006). Small ring infiltration was determined in El Batán as reported in Govaerts et al. (2007a). Infiltration during irrigation was measured for the third auxiliary irrigation in the 2007-2008 season in Obregón. Inflow was measured with a calibrated bucket at the beginning of one furrow per main plot at regular time intervals. Outflow was monitored per main plot with a V-notch weir of 30°. Soil moisture content was determined volumetrically once a week during the 2007 season in El Batán and the 2007-2008 season to a depth of 60 cm. Soil microbial biomass C and N were measured as reported in Govaerts et al. (2007b) and Limon-Ortega et al. (2006).

Results and Discussion

Soil Aggregation

As well in the rainfed trial as in the irrigated trial, the mean weight diameter (MWD) of both dry and wet sieving was the highest when all residues were retained on the surface of the zero till fields. The removal of crop residue in rainfed conditions and the burning of residue in irrigated conditions degraded soil structure as compared to the (partial) retention of the residue (Figure 1). Chan et al. (2002) also found that stubble burning significantly lowered the water stability of aggregates in the fractions >2 mm and < 50 pm. Govaerts et al. (2007c) obtained similar results in a rainfed permanent raised bed planting system in the subtropical highlands of Mexico, where the MWD of dry and wet sieving decreased with decreasing amounts of residues retained, although partial residue removal by baling kept aggregation within acceptable limits. This indicates that total removal of residues has to be avoided, but it is not always necessary to retain all crop residues in the field to achieve the benefits of permanent raised beds or zero tillage on the flat systems. The management of previous crop residues is key to soil structural development and stability since organic matter is an important factor in soil aggregation. Fresh residue forms the nucleation centre for the formation of new aggregates by creating hot spots of microbial activity where new soil aggregates are developed (De Gryze et al., 2005). In addition, the retention of crop residue on the soil surface decreases the breakdown of aggregates by protecting them against raindrop impact (Le Bissonnais, 1996).

Water Infiltration

Time-to-pond

Time-to-pond is a measure for the direct infiltration in the soil. In the rainfed trial, time-to-pond was lower for zero tillage with removal of residue than with (partial) residue retention, but the difference was only significant in the maize

Rennowal Ful rgiention

Res due management DIY üVJ'rt aiewnD

Figure 1. The effect of residue management on mean weight diameter obtained by dry and wet sieving (mm) in the zero till treatments of (a) the rainfed trial in El Batán and (b) the irrigated trial in Ciudad Obregón (Adapted from Limon-Ortega et al. 2006). Values with different letters differ significantly at 5% based on least square difference grouping. Bars indicate standard

error.

phase of the rotation (Figure 2). In plots with wheat time-to-pond was higher than in plots with maize and differences between treatments were smaller. The standing crop induces a 'vertical' mulching effect that is smaller in maize plots since plant density is lower. In irrigated conditions, time-to-pond increased with increasing retention of residue at the soil surface. Burning of residue resulted in the lowest direct infiltration (Figure 2). The retention of crop residue at the surface prevents surface crust formation by increasing aggregate stability compared to zero tillage with residue removal or burning (Figure 1; Li et al. 2007; Chan et al. 2002) and protecting aggregates from direct raindrop impact (Le Bissonnais 1996). In addition, the residues left on the top soil with zero tillage and crop retention act as a succession of barriers, reducing the runoff velocity and giving the water more time to infiltrate. The residue intercepts rainfall and releases it more slowly afterwards (Scopel and Fideling 2001).

Rpit^aji >Vi«Ti-mi(.H H-MlWu-Lil.ji Fhfc rrKtrfi

itipnf]

U-'linri

RtudLi mmapeniirr

(a) (b)

Figure 2. The effect of residue management on time-to-pond (s) in the zero till treatments of (a) the rainfed trial in El Batán during the maize and wheat phase of the rotation and (b) the irrigated trial in Ciudad Obregón during the wheat phase of the rotation. Values with different letters differ significantly at 5% based on least square difference grouping. Bars indicate standard error.

Small Ring Infiltration in Rainfed Conditions

The small ring infiltration measurements in the rainfed trial showed similar results than the time-to-pond. When residue was removed, the time to infiltrate a volume of 250 ml was higher than when residue was retained, before sowing as well as after harvest (Figure 3). The retention of residue stimulates biological activity by earthworms, increasing the connectivity of macropores, an important factor in infiltration (McGarry et al., 2000).

Figure 3. The effect of residue management on the time (s) needed to infiltrate 250 ml of water in the zero till treatments of the rainfed trial in El Batán during the wheat and maize phase of the rotation (Adapted from Govaerts et al. 2007a)

with BS before sowing and AH after harvest.

Infiltration during Irrigation

In irrigated conditions, the permanent raised beds where residue was burned had an irrigation water outflow that became equal or higher than the irrigation water inflow approximately 6 hours after initiating the irrigation. In contrast, for permanent raised beds where residue was retained at the soil surface the outflow remained lower than the inflow during the whole irrigation (Figure 4). Outflow started sooner where residue was burned than where it was retained, reflecting the faster advance of water in the burned treatment. An increased advance of the water in the furrows will reduce the time for infiltration. Similarly, outflow stopped sooner when the irrigation was stopped where residue was burned than where it was retained (Figure 4). This resulted for permanent raised beds with residue burned in a very low average irrigation efficiency of 24% compared to 52% for permanent raised beds where residue was retained. The low infiltration with residue burning is related to the low aggregate stability in this practice compared to residue retention (Figure 1). The reduction infiltration might be enhanced by the reduced cracking with burning compared to retention (data not shown), since the cracks may be important pathways for infiltration in these heavy clay soils.

Time 3hcf s^n .mm

Figure 4. The effect of residue management on infiltration and outflow of irrigation water in the zero till treatments of the irrigated trial in Ciudad Obregôn with In Inflow (l/s), Out Outflow (l/s), Burn Residue burning, Retain Full residue

retention and 1 and 2 field repetitions.

Soil Moisture Content

The increased infiltration with residue retention in zero tillage systems was reflected in the soil moisture content throughout the growing season. In the rainfed trial, soil moisture content in the top 60 cm of the zero till plots was lower when residue was removed compared to when residue was retained. Similarly, in the irrigated trial, soil moisture

(a) (b)

Figure 5. The effect of residue management on moisture content in the profile (0-60 cm) throughout the growing season in the wheat phase of the rotation in the zero till treatments of (a) the rainfed trial in El Batán and (b) the irrigated trial in Ciudad Obregón (irrigations 28 days before and 43, 71 and 95 days after planting).

content was lower when residue was burned than with a surface mulch cover. The difference between practices was smaller in irrigated conditions, probably due to the mitigating effect of irrigation. Also Gicheru et al. (1994) showed that crop residue mulching resulted in more moisture down the profile (0-120 cm) throughout two seasons (a short rains period and a long rains period) within 2 years than conventional tillage and tied ridges in a semi-arid area of Kenya. More soil water enables crops to grow during short-term dry periods and reduces sensitivity to drought stress of the system, which is especially important in rainfed systems.

Microbial Biomass

Soil microbial biomass C and N decreased with decreasing amount of residue retained on the soil surface in the zero till treatments of both the rainfed and the irrigated long-term trial (Table 1). The soil microbial biomass reflects the soil's ability to store and cycle nutrients (C, N, P and S) and organic matter (Dick, 1992; Carter et al., 1999) and plays an important role in physical stabilization of aggregates (Franzluebbers et al., 1999). General suppression is also related to total soil microbial biomass, which competes with pathogens for resources or causes inhibition through more direct forms of antagonism (Weller et al., 2002). Consequently, soil microbial biomass is considered an important indicator of soil quality. The rate of organic C input from plant biomass is generally considered the dominant factor controlling the amount of microbial biomass in soil (Campbell et al., 1997). Franzluebbers et al. (1999) showed that as the total organic C pool expands or contracts due to changes in C inputs to the soil, the microbial pool also expands or contracts. The continuous, uniform supply of C from crop residue retention serves as an energy source for microorganisms.

Table 1. The effect of residue management on soil microbial biomass C and N (SMB C and SMB N) in the wheat phase of the rotation in the zero till treatments of the rainfed trial in El Batán (0-15 cm; Adapted from Govaerts et al. 2007b) and the irrigated trial in Ciudad Obregón (0-7.5 cm; Adapted from Limon-Ortega et al. 2006).

Trial Residue management SMB C (mg C kg-1 soil) SMB N (mg N kg-1 soil)

Rainfed, El Batán Removal 288 B 22 A

Full retention 453 A 20 A

Irrigated, Cd. Obregón Burning 540 b 22 c

Removal 617 ab 25 b

Partial retention 681 a 25 b

Full retention 687 a 31 a

Values with different letters differ significantly at 5% based on least square difference grouping.

Chemical Soil Quality

Removing crop residues is associated with a decrease in soil organic matter compared to zero tillage with residue retention (Blanco-Canqui and Lal, 2007), as observed in the rainfed trial. Despite continuous C input in the treatments with residue retention, soil organic matter did not differ from the treatment with residue removal in the irrigated trial. If soil microbial biomass is used as an early indicator of soil organic matter, however, the same trend can be expected in irrigated conditions. In the rainfed trial, removal of residues resulted in a lower nutrient status based on the concentration

of C, N, K and Zn, compared to retention of residues. Only the continuous wheat treatment with residue removal approached the zero tillage treatments with residue retention. In the irrigated permanent raised bed system, total N content was 1.14 times lower in when straw was burned than when straw was retained. The N-mineralization rate was similar for the treatments with straw retained and burned, but greater for the PB-straw partly removed treatment where only wheat straw was retained. This result is presumably related to the C-N ratio of the maize left on the field in PB-straw retained. It has often been reported that during the decomposition of organic matter, inorganic N can be immobilized (Zagal and Persson, 1994), especially when organic material with a large C-N ratio is added to soil. The soil sodicity and P concentration were generally greater when residues were burned compared to the other treatments. Similarly, Govaerts et al. (2007c) observed higher K, N, C and lower Na concentrations with residue retention compared to residue removal in a rainfed permanent raised bed planting system in the subtropical highlands of Mexico.

Implications for Crop Production

In the rainfed, semi-arid zero tillage system, yields were significantly and at least 50% higher with crop residue retention than with residue removal. Zero tillage treatments with partial residue removal gave yields equivalent to treatments with full residue retention (Govaerts et al., 2005). Crop performance was related to soil moisture and the related attributes infiltration, soil structure and organic matter, showing that soil moisture is the main limiting factor of the system (Verhulst et al., 2008). It is therefore essential for the sustainability of any management practice developed for rainfed, semi-arid systems that soil water capture and storage are optimal. Zero tillage with removal of all crop residues resulted in low aggregation and aggregate stability, infiltration and soil moisture content and is not a sustainable management option for the semi-arid highlands. Zero tillage with residue retention will result in higher soil quality and more stable and higher yields in these systems. However, competitive demands for crop residues at farm level (e.g. for use as animal fodder, fuel, or construction material) are high in semi-arid rainfed systems and can constitute serious bottlenecks to the implementation of zero tillage with residue retention (Erenstein, 2002). More research is needed to establish minimum residue retention levels (thresholds).

In the irrigated permanent raised bed system, yield differences between management practices only became clear after 5 years (10 crop cycles), with a dramatic overall reduction in the yield for permanent raised beds where all residues had been routinely burned (Sayre et al., 2005). In contrast to rainfed low rain fall areas, in irrigated agricultural systems (at least in tropical, semi-tropical and the warmer, temperate areas), the application of irrigation water appears to 'hide or postpone' the expression of the degradation of many soil properties associated with continuous residue burning until they reach a level that no longer can sustain high yields, even with irrigation. The difference in soil moisture content between residue management practices was smaller in irrigated than in rainfed conditions due to the correcting effect of irrigation, allowing other factors such as nutrient availability to become more important than in rainfed conditions. Since biomass production is higher in irrigated conditions than in rainfed, semi-arid conditions, there is more scope for the removal of part of the crop residue for other uses. In the permanent raised bed systems where only 25 cm of standing stubble remained in the field (the removal treatment), aggregation, direct infiltration soil microbial biomass and yields remained within acceptable limits (Figure 1, 2 and Table 1; Sayre et al., 2005). Burning all residues resulted in a degradation of soil quality comparable to the removal of all residues in the rainfed semi-arid system, where almost no standing stubble was left in the field in order to simulate the conditions caused by the livestock grazing pressure that is common in these systems.

Conclusions

In both zero till systems, the retention of (part of) the crop residues was necessary to maintain soil quality. In the rainfed semi-arid zero tillage system, mean weight diameter obtained by dry and wet sieving, infiltration, soil moisture content, soil microbial biomass and nutrient status were lower with residue removal than with residue retention. In the irrigated permanent raised bed system, burning of all crop residues resulted in a degradation of soil structure, lower direct infiltration, irrigation efficiency, soil moisture content, soil microbial biomass, total N and greater soil sodicity as compared to retaining crop residue at the surface. Practices with partial retention of crop residue showed soil quality similar to practices with retention of all residues. Especially under rainfed semi-arid production conditions, the best use of crop residues is to retain them in the field as part of the implementation of sound conservation agriculture technologies, although it may be possible to remove part of the residue for other uses. In irrigated conditions where biomass production is higher, there is more scope for the removal of part of the residue. More research is needed to establish minimum residue retention levels (thresholds) with positive impacts on soil quality and crop production.

Acknowledgements

N.V. received a PhD fellowship of the Research Foundation - Flanders. We thank M. Ruiz Cano, J. Gutierrez

Angulo, J. Sanchez Lopez, A. Zermeño, C. Rascon, B. Martínez Ortiz, A. Martinez, M. Martinez, H. González Juárez,

J. Garcia Ramirez and M. Perez for technical assistance. The research was funded by the International Maize and

Wheat Improvement Center (CIMMYT, Int.) and its strategic partners and donors.

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Conservation Agriculture - Constraints, Issues and Opportunities

in Rainfed Areas

B. Venkateswarlu, K.L. Sharma and J.V.N.S. Prasad

Central Research Institute for Dryland Agriculture, Hyderabad, 500 059, Andhra Pradesh, India (Email: director@crida.ernet.in/vbandi_ 1953@yahoo.com)

In India, out of 142.2 m ha net cultivated area, about 87 m ha is unirrigated. While the irrigated area produces about 56% of total food requirement, remaining 44% of the total food production is supported by rainfed agriculture. Most of the essential commodities such as coarse cereals (90%), pulses (87%), and oil seeds (74%) are produced from the rainfed agriculture. In view of the stagnating productivity levels of irrigated agriculture, the contribution from the rainfed agriculture should increase to meet the requirements of the growing population. In India, the total degraded area accounts to 120.7 m ha, of which 73.3 m ha was affected by water erosion, 12.4 m ha by wind erosion, 6.64 m ha by salinity and alkalinity and 5.7 m ha by soil acidity (Anonymous 2008). Land degradation is a major threat to our food and environmental security and the extent of degradation is more pronounced in rainfed regions.

Due to growing resource degradation problems world wide, conservation agriculture has emerged as an alternative strategy to sustain agricultural production. Conservation agriculture (CA) is a concept for resource-saving agricultural crop production that strives to achieve acceptable profits together with high and sustained production levels while concurrently conserving the environment (FAO 2007). CA is based on enhancing natural biological processes above and below the ground. Interventions such as mechanical soil tillage are reduced to an absolute minimum, and use of external inputs such as agrochemicals and nutrients of mineral or organic origin are applied at an optimum level and in a way and quantity that does not interfere with, or disrupt, the biological processes. CA is characterized by four principles that are linked to each other. They are (i) minimum mechanical soil disturbance for erosion control, (ii) maintenance of permanent organic soil cover, (iii) diversified crop rotations for pest and disease control, conserving bio-diversity and (iv) controlling in field traffic for reducing the compaction. However, in practice, zero tillage and residue retention have emerged as the two cardinal principles of CA.

Conservation agriculture is practiced on over 96 m ha area world wide, most of it is in USA, Brazil, Argentina, Canada and Australia. CA became an acceptable practice for the farmers in these countries due to decades of research and extension and concerns of the farmers, scientists and the public on soil erosion. Due to the efforts of the Rice-Wheat Consortium and several institutions of the national agricultural research system, zero till technology has been introduced into India and neighboring countries and it is currently adopted by farmers in over 2 million ha largely in the Indo-Gangetic plains. World-wide, CA or no-till farming has spread mostly in the rainfed agriculture. However, in India its success is more in irrigated belt of the Indo-Gangetic plains. Considering the severe problems of land degradation due to runoff induced soil erosion, rainfed areas particularly in arid and semi-arid regions require the practice of CA more than the irrigated areas in order to ensure a sustainable production. This chapter reviews the constraints and scope of CA in areas other than the Indo-Gangetic plains of the country, focusing on arid and semi arid zones.

Rainfed Production Systems

Unlike the homogenous growing environment of the IGP, the production systems in arid and semi-arid regions are quite heterogeneous and diverse in terms of land and water management and cropping systems. These include the core rainfed areas which cover upto 60-70% of the net sown area and the irrigated production systems in the remaining 30-40% area. The rainfed cropping systems are mostly single cropped in the red soil areas while in the black soil regions, a second crop is taken on the residual moisture. In rabi black soils, farmers keep lands fallow during kharif and grow rabi crop on conserved moisture. The rainfall ranges from >500 mm in arid to 1000 mm in dry sub-humid. Alfisols, Vertisols, Inceptisols and Entisols are the major soil orders. Soils are sloppy and highly degraded due to continued erosion by water and wind. Sealing, crusting, sub-surface hard pans and cracking are the key constraints which cause high erosion and impede infiltration of rainfall. The choice and type of tillage largely depend on the soil type and rainfall. Leaving crop residue on the surface is another important component of CA, but in rainfed areas due to its competing uses as fodder, little or no residues are available for surface application.

The key principles of rainfed agriculture rely on soil and water conservation, both essential components of the CA. Tillage in rainfed areas is mostly carried out for seed bed preparation and interculture operations for weed control and does not use heavy equipment. Though conserving both soil and water are equally important; in low to medium rainfall regions, more priority is given for conservation of rainfall by facilitating better infiltration and reduced runoff. That is why, deep tillage once in three years is suggested to promote greater infiltration of rainwater and control weeds. This also breaks the sub surface hard pan. However, practices like chiseling can meet the objective of breaking the hard pan without soil inversion associated with deep tillage.

Experience from several experiments in the country showed that minimum or reduced tillage does not offer any advantage over conventional tillage in terms of grain yield without incorporation of surface residue. Leaving surface residue is key to control runoff, soil erosion and hard setting in rainfed areas which are the key problems. In view of the shortage of residues in rainfed areas in arid and semi-arid regions, several alternative strategies have emerged for generation of residues either through in situ cultivation and incorporation as a cover crop or harvesting from perennial plants grown on bunds and adding the green leaves as manure cum mulching. Agroforestry and alley cropping systems are other options where biomass generation can be integrated along with crop production. This indicates that the concept of CA has to be understood in a broader perspective in arid and semi-arid areas which includes an array of practices like reduced tillage, land treatments for water conservation, on-farm and off-farm biomass generation and agroforestry. Here, conservation tillage with residue retention on surface are more appropriate than zero tillage which is emphasized in irrigated agriculture. Experiences on zero or reduced tillage, residue incorporation, stubble mulching, green leaf manuring and land treatments for water conservation from rainfed cropping systems within the arid and semi arid regions are presented below.

Conservation Tillage in Rainfed Cropping Systems

As mentioned earlier, conservation tillage is a more appropriate strategy for rainfed production systems to promote CA. Conservation tillage is a generic term encompassing many different soil management practices. It is generally defined as 'any tillage system that reduces loss of soil or water relative to conventional tillage; mostly a form of non-inversion tillage, allows protective amount of residue mulch on the surface. According to Lal (1989), conservation tillage i) allows crop residues as surface mulch, ii) is effective in conserving soil and water, iii) maintains good soil structure and organic matter contents, iv) maintains desirably high and economic level of productivity, v) cut short the need for chemical amendments and pesticides, vi) preserves ecological stability and vii) minimizes the pollution of natural waters and environments. In other words, the basic principles of conservation tillage and dryland agriculture are essentially same.

Several experiments were conducted to assess the impact of tillage, land treatments and mulching on different rainfed crops across the country. Under semi-arid conditions at Hyderabad, summer tillage helped in higher soil moisture retention by 20%, reduced weed infestation by 40% and contributed to higher yields (Table 1).

Table 1. Effect of off-season tillage on grain yields of sorghum and castor in Alfisols at Hyderabad

Practice Sorghum grain yield* (t/ha) Castorbean** (t/ha)

Without off-season tillage 1.87 0.32

With off-season tillage 2.60 0.31

* Mean of three seasons; ** Mean of two seasons

Table 2. Effect of land shaping on the yields of wheat and chickpea in sub- montane soils at Ballowal-Saunkhri and pearlimillet in alluvial soils of Agra

Land shaping Wheat and chickpea mixture, 3 seasons (t/ha) Pearlmillet (t/ha)

Rainfall 320 mm Rainfall 660 mm

Normal planting 1.05 1.34 2.22

With land leveling 1.65 1.63 2.31

In sub-montane region of Hoshiarpur in Punjab and in the Inceptisols at Agra, land shaping resulted in higher crop yields. The benefits were seen mostly in low rainfall years owing to even distribution of soil moisture due to leveling (Table 2).

Practices like contour cultivation, and cultivation on graded bunds help in effective conservation of moisture. These practices reduce runoff up to 40% and contribute to yield increments up to 25-35% depending on the rainfall situation. The most important conservation practice acceptable to farmers is the ridge and furrow system of planting. Several trials across different soil types and rainfall zones conclusively proved the advantages of ridge and furrow systems over flat planting. Ridges and furrows reduce runoff and help in insitu moisture conservation. Response to ridges and furrows in a number of coarse cereal and legume crops was more in moderate rainfall regions than either severely drought prone or high rainfall regions (Table 3).

Table 3. Response of coarse cereal and legumes crops to land treatments under different intensities of drought

Crops (seasons) Grain (t/ha) Response (%)

Flat planting Ridges - Furrows

Severe Drought

Coarse cereals (19) 1.73 2.02 17

Legumes (24) 0.71 Moderate Drought 0.78 10

Coarse cereals (12) 1.51 1.92 28

Legumes (1) 0.30 Less Prone to Drought 0.42 40

Coarse cereals (1) 0.79 0.91 15

Straw and soil mulching are other simple practices that conserve moisture. The effect of mulching is seen more in rabi crops than kharif crops. Advantages of mulching was noted both under adequate and sub-optimum soil moisture. Shallow and fibrous rooted crops benefit more than deep rooted crops from mulching. In deep Vertisols, cracks are common due to swelling and shrinking properties of these soils. Once the cracks are sealed due to rainfall, the soil does not allow any further infiltration. Under such conditions, vertical mulching is recommended which helps in maintaining the gaps between the cracked surfaces and protects the soil from sealing. Trials showed that crop like rabi sorghum was benefited significantly from vertical mulching.

However, experiments on reduced or zero tillage in arid and semi arid climatic regions did not give encouraging results so far. Farmers generally adopt a system of plough planting which can be considered as minimum tillage. However, this practice is not suitable for deep black soils due to heavy weed infestation and reduction in infiltration of water. In arid regions, zero tillage was found to be significantly inferior to conventional tillage with pearl millet. Pearl millet yields were higher under conventional tillage over no tillage for four years continuously (Table 4). In the fourth year, the crop completely failed in the no-till plot. The root growth was poor and considerable reduction in biomass production was noted due to reduction in initial plant population. The benefits of residue on the surface have not been tried as the authors suggest that pearl millet residues are highly prized as fodder in arid regions which face acute scarcity of fodder. Alternatively, the use of residues of mustard and sesame are suggested which are not used as fodder.

In a long term experiment (8 years) carried out under semi-arid conditions at Hyderabad, conventional tillage and minimum tillage (plough planting) were compared for their effect on yields and sustainable yield index of sorghum and castor in a rotation. Minimum tillage was inferior to conventional tillage due to heavy weed infestation and reduction in infiltration of water due to compaction of the surface soil (Table 5).

Table 4. Yields of Pearl millet under conventional and no-tillage conditions Under arid conditions at Jodhpur

Year Pearl millet yield (q/ha)

Conventional Tillage No-tillage

1995 6.48 5.84

1996 9.09 2.26

1997 7.14 2.26

1998 3.83 -

Source: Aggarwal et al 1998

Table 5. Long-term effects of land management on crop yields and sustainable yield index (8 years)

Residues Sorghum (kg/ha) Castor (kg/ha) SYI

Conventional Plow Conventional Plow Conventional Plow

tillage planting tillage planting tillage planting

Sorghum 1127 810 820 477 0.49 0.35

Gliricidia loppings 1201 895 925 507 0.50 0.37

No residue 1103 840 840 448 0.48 0.31

Mean 1144 848 862 477 0.49 0.34

Tillage ** ** *

Residue ** ** *

T x R NS NS NS

SYI - Sustainability Yield Index, NS - Non-significant at P > 0.05 *Significant difference at P = 0.05, "Significant difference at P = 0.01 Source: Sharma et al, 2005

In another experiment involving sorghum and mung bean rotation, conventional and reduced tillage were compared in a 8-year study (1998-2005). The pooled analysis indicated that reduced tillage across all integrated nutrient management treatments remained consistently lower in terms of sorghum grain yield but at the end of 8 years, the yields came close to the conventional tillage indicating that it takes long period under semi-arid conditions before reduced tillage comes on par with the conventional tillage (Fig.1).

HÉ 3MD HD1 ¿M2 J-IÜ J JMS SIDE. J»T

Figure 1. Sorghum grain yield over years (1998-2007) as influenced by conventional and reduced tillage under semi arid conditions at Hyderabad. (Sharma et al 2009)

In a network project on tillage conducted since 1999 at various centers of the All India Coordinated Research Project for Dryland Agriculture, it was found that rainfall and soil type had a strong influence on the performance of reduced tillage (Ramakrishna et al 2005). In arid regions (<500 mm rainfall), low tillage was found on par with conventional tillage and weed problem was controllable in arid inceptisols and aridisols. In semi arid (500-1000 mm) region, conventional tillage was superior. However, low tillage + interculture was superior in semi-arid Vertisols and low tillage + herbicide was superior in Aridisols. In sub-humid (>1000 mm) regions, weed problem was severe depending on the rainfall distribution. In this zone, there is a possibility of reducing tillage intensity by using herbicide. Thus, there is a possibility of greater success of minimum tillage in high rainfall sub-humid regions.

Utera cropping is an important practice followed by farmers in eastern India which has all elements of the conservation farming. Crops like lathyrus and linseed are grown as a relay crops after rainfed low land paddy which minimizes the cost of tillage and takes advantage of the residual moisture. However, the productivity is low due to poor crop stand of utera crop. Improvements can be made both through better crop choices and agronomic management of the utera crop and manipulation of the stubble height of the paddy crop at harvest.

Critical Gaps and Researchable Issues

• The success of conservation agriculture in rainfed areas depends on two critical elements, viz., residue retention on surface and weed control. Since residues are generally used as fodder in drylands, there is a need to determine the minimum residue that can be retained without affecting the crop-livestock system. Initially, emphasis may be given for crops whose residues are not used as fodder.

• More research on weed management under minimum tillage in a cropping system perspective.

• Identification of alternative sources of fodder for livestock to spare crop residue for conservation farming.

• Identification of critical thresholds of tillage for various rainfall, soil and cropping systems, such that the main objectives of rainwater conservation are not compromised. This will balance the need for conserving soil and capture rainwater in the profile.

• Farm implements needed for seed and fertilizer placement simultaneously for ensuring optimum plant stand, early seedling vigour in rainfed crops under minimum tillage.

• Control of termites in order to enhance the value of residue left on surface during long interval period between two crops.

Summary

Conservation agriculture in arid and semi-arid regions has to be understood in a broader perspective. It should involve both soil and water conservation methods mutually reinforcing each other. Conservation tillage appears more appropriate under rainfed agriculture than zero tillage. Tillage alone without residue retention may not be of much utility. Therefore, the real challenge lies in ways and means of sparing the crop residue for conservation farming and find out alternative strategies of meeting fodder requirements of livestock. CA practice has to be adopted holistically so that it minimizes soil loss, conserves water and controls weeds which are essential for success of crop production under rainfed conditions.

References

Aggarwal RK, Praveen Kumar singh YV, Lodha S 1998. Enhancing fertilizer use efficiency in conjunction with residue management in dryland crops and cropping systems in low rainfall conditions. Indo-US Project, Consolidated work report, 1990-98.

Anonymous 2008. Harmonisation of wastelands/degraded lands datasets of India. Published by National Rainfed Area Authority (NRAA), Ministry of Agriculture, Government of Inida, NASC Complex, DP Sastri Marg, New delhi-110012, 5 p.

Food and Agriculture Organization (FAO). 2007. Agriculture and Consumer Protection Department. Rome, Italy Available from http:// www.fao.org/ag/ca/

Lal R 1989. Conservation tillage for sustainable agriculture: tropics versus temperate environments. Advances in Agronomy 42: 86-197.

Ramakrishna YS, Vittal KPR, Sharma KL 2005. Conservation agricylture in rainfed semi arid tropics- Some past experiences. Lessons learnt and future scopes. In: Conservation agriculture-Status and Prospects. Eds. IP Abrol, RK Gupta and RK Mallik. Centre for Advancement of Sustainable Agriculture, New Delhi, pp 242.

Sharma K L, Kusuma Grace J, Srinivas K, Ramakrishna Y S, Korwar G R, Maruthi Sankar G, Uttam Kumar Mandal, Ramesh V, Hima Bindu V, Madhavi M, and Pravin Gajbhiye 2009. Influence of Tillage and Nutrient Sources on Yield Sustainability and Soil Quality under Sorghum-Mung Bean System in Rainfed Semi-Arid Tropics. Communications in Soil Science and Plant Analysis (In Press).

Sharma KL, Mandal UK, Srinivas K, Vittal KPR, Biswapati Mandal, Kusuma Grace, Ramesh V 2005. Long term soil management effects on crop yields and soil quality in dryland alfisol. Soil and Tillage Research 83:246-259.

Session 1.2: Input Management (Water, Nutrients, Seed and Agro-chemicals)

Perspectives on Nutrient Management in Conservation Agriculture*

Amir Kassam1 and Theodor Friedrich2

Plant Production and Protection Division, Food and Agriculture Organization of the United Nations, Viale

delle Terme di Caracalla, 00153 Rome, Italy (1 kassamamir@aol.com; 2Theodor.Friedrich@fao.org)

Conservation Agriculture (CA) systems aim at enhancing soil health and function as a precursor to sustainable production intensification. Nutrient management in CA must be formulated within this framework of soil health. Thus, nutrient management strategies in CA systems would need to attend to the following four general aspects, namely that: (i) the biological processes of the soil are enhanced and protected so that all the soil biota are microorganisms are privileged and that soil organic matter and soil porosity are built up and maintained; (ii) there is adequate biomass production and biological nitrogen fixation for keeping soil energy and nutrient stocks sufficient to support higher levels of biological activity, and for covering the soil;(iii) there is an adequate access to all nutrients by plant roots in the soil, from natural and synthetic sources, to meet crop needs; and (iv) the soil acidity is kept within acceptable range for all key soil chemical and biological processes to function effectively.The paper discusses in general terms the above four aspects of nutrient management in CA systems.

Key words: Conservation Agriculture, Soil Health, Nutrient Management

Fundamentally, CA is underpinned by biologically-framed management practices, the so called 'second-paradigm approaches' as enunciated by Sanchez (1994). As such, soil organic matter and soil biota are essential components in the complex system of interactions related to soil health and crop productivity. They provide a basis for optimizing the use of inorganic soil amendments and plant nutrients so that there is a positive-sum effect on agricultural productivity and the environment. Since the second-paradigm approaches are relatively new, little systematic research has been done on how to harness the potentials of biologically-framed agricultural production systems. However, an exciting glimpse of the scientific foundations of this emerging biological paradigm for agricultural production systems and its empirical accomplishments can be obtained from the work of a number of scientists presented in a single volume by Uphoff et al. (2006).

Conservation Agriculture (CA) systems are defined by three key elements, namely: no or minimal mechanical soil disturbance, permanent organic soil cover specially by crop residues and cover crops, and diversified crop rotations in the case of annual crops or crop associations in case of perennial crops, including legumes. These elements in various combinations aim at establishing and sustaining healthy soil systems that can offer the best crop and livestock productivities and environmental services within the prevailing ecological and socio-economic conditions while optimizing the use of agrochemicals with biological interventions. CA system principles cannot be applied in a standardized prescriptive manner, and therefore in many ways they do represent a radical departure from the prevailing tillage-based mono-cropped production systems that depend dominantly on external inputs of mineral fertilizer and pesticides to maintain crop productivity and output.

Soil health is the capacity of the soil to function as a living system in which soil biological processes or the endogenous inputs are utilised alongside any exogenous inputs required to achieve the desired level of agricultural production that is economically and environmentally sustainable. Thus, with CA systems, the establishment and maintenance of healthy soil condition is inextricably linked to the achievement of effective nutrient management.

This paper elaborates on the notion of soil health in CA system as a precondition for effective nutrient management, and discusses in general terms four broad elements that need to be considered in nutrient management strategies for CA systems.

Soil Health and Conservation Agriculture

For a soil to be productive for agricultural use, it must inter alia have the space for plant roots to grow, to hold and make water and nutrients available to plant roots, and provide a conducive biotic and chemical environment for soil microorganisms to function to maintain soil porosity, fix atmospheric nitrogen, hold and mineralize nutrients. All these dimensions must operate together and form the basis of soil health as defined below (Derived by combining

*The views expressed in this paper are the personal opinions of the authors and do not necessarily quote the official policy of FAO

Doran and Zeiss; Wolfe; and Trutmann, quoted together on http://ppathw3.cals.cornell.edu/mba_project/moist/ TropSCORE.html.)

"Soil health is the capacity of soil to function as a living system, with ecosystem and land use boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health. It emphasises a unique property of biological systems, since inert components cannot be sick or healthy.

Healthy soils maintain a diverse community of soil organisms that help to control plant disease, insect and weed pests, form beneficial symbiotic associations with plant roots (e.g., nitrogen-fixing bacteria and mycorrhizal fungi); recycle essential plant nutrients; improve soil structure (e.g., aggregate stability) with positive repercussions for soil water and nutrient holding capacity, and ultimately improve crop production.

Examples of management practices for maximizing soil health would include maintaining vegetative cover on the land year-round to increase organic matter input and minimize soil erosion, more reliance on biological as opposed to chemical approaches to maintain crop productivity (e.g., rotations with legume and disease-suppressive cover crops), and avoiding physical (mechanical) interventions which might compact, alter or destroy the biologically-created porous structural arrangements of soil components."

In many parts of the world soils are acknowledged to be sick, in poor health, and falling in potential for self-sustaining productivity. While there is much talk of 'soil quality' as if it were a static and sufficient characteristic, there is less-frequent mention of 'soil health', referring particularly to the biological dynamics of soil quality. (A relevant definition of Soil Health has been given above).

If plants we see above-ground don't thrive because soil is in poor condition, then probably the life below ground doesn't thrive either (= is 'sick'), for the same reasons, jeopardizing the effectiveness of the mutual interdependence of the above-and below-ground parts of the soil/plant system. It is easy to see the symptoms above-ground, but more difficult (as yet) to discern and characterize them below the surface.

Soil in 'good condition' (static) or 'good health' (dynamic) benefits from the following key components of CA (Shaxson et al. 2008):

Minimum disturbance of optimum porous soil architecture, which provides/maintains: (a) Optimum proportions of respiration gases in the rooting-zone, (b) Moderates organic-matter oxidation; (c) Porosity to water movement, retention and release at all scales, and (d) Limits re-exposure of weed seeds and their germination.

A permanent covering of sufficient organic matter (esp. crop residues) over the soil surface, which provides: (a) Buffering against severe impact of solar radiation and rainfall; (b) A substrate for soil organisms' activity; (c) Raised cation-exchange capacity for nutrient capture, retention and slow-release; and (d) Smothering of weeds

Cropping sequences and rotations which include legumes, providing: (a) Minimal rates of build-up of populations of pest species, through life-cycle disruption; (b) Biological N-fixation in appropriate conditions, limiting external costs; (c) Prolonged slow-release of such N from complex organic molecules derived from soil organisms; (d) Range of species, for direct harvest and/or fodder; and (e) Soil improvement by organic-matter addition at all depths reached.

In light of the above elaboration of soil health and CA, it is clear that scope of the topic of nutrient management in CA systems is extremely wide and complex. Nor do we believe that enough scientific research has been done on nutrient management aspects to explain most of the productivity-related ecological process at work. Instead, the following sections offer some general perspectives on four elements of nutrient management in CA.

Elements of a Nutrient Management Strategy in CA

Being a biologically-based practice with an agro-ecological perspective, CA does not focus on a single commodity or species. Instead, it addresses the complex interactions of several crops to particular local conditions capitalizing on the complex systems of interactions involved when managing soil systems productively and sustainably. An illustration of soil system dynamics under CA developed from the work of Lucien Séguy and CIRAD researchers in several countries is given in Uphoff et al. (2006).

Therefore nutrient management practices in CA systems cannot be reduced to simple physical input-output model. While there is much new work that needs to be done to formulate nutrient management strategies in CA

systems, it would seem to us that all such strategies would need to ensure that soil health as elaborated above becomes the means of meeting crop nutrient needs in an optimum and cost-effective way within the prevailing ecological and socio-economic conditions.

Nutrient management strategies in CA systems would need to attend to the following four general aspects, namely that: (i) the biological processes of the soil are enhanced and protected so that all the soil biota are microorganisms are privileged and that soil organic matter and soil porosity are built up and maintained; (ii) there is adequate biomass production and biological nitrogen fixation for keeping soil energy and nutrient stocks sufficient to support higher levels of biological activity, and for covering the soil; (iii) there is an adequate access to all nutrients by plant roots in the soil, from natural and synthetic sources, to meet crop needs; and (iv) the soil acidity is kept within acceptable range for all key soil chemical and biological processes to function effectively.

The above four elements are elaborated below but without engaging in a comprehensive discussion regarding how they are affected by the level of production, climate and seasonality, water supply, soil type, clay content and type etc, or by farm size and resources, or type of farm power and mechanization, etc. Based on our assessment of the situation, it would be true to say that not enough is known about these four elements to formulate a comprehensive framework for nutrient management in CA systems.

Managing Soil Biological Processes - Soil as a Living System

From many physical landscapes, we expect the three-dimensional catchments which are clothed in soil to yield sufficient crops and other vegetation of various types and, simultaneously, volumes of clean water from streams and boreholes regularly on a repeated annual basis.

Plants, rivers and groundwater depend on water penetrating into soil which is porous from the surface downwards. Insufficiency of water for plants hinders the interacting functioning of the other components of soil productivity: biological, physical, and chemical. The rate of entry of water into and through and its movement within the soil is governed by soil's porosity, both micro and macro, which in turn is governed by the volume and inter-connectedness of pores able to transmit water. The volume and availability of water which plants can use is determined by the proportion of soil pores which can retain water against the force of gravity and yet can release that water in response to 'suction' exerted through roots as dictated by the plants' physiology and atmospheric demand. Water management in soil is intrinsically linked to nutrient management.

Insufficiency of water and/or of various nutrients required by plants for growth processes diminish the derived productivity of the soil in which they are growing, inhibiting full interactions in the plant-soil system. Inadequacy of plant nutrients hinders plant growth and development; severe water-stress stops the whole system.

Soil porosity is damaged or destroyed by compaction, pulverization, and/or collapse due to degradation and loss of organic matter. Net loss of organic matter is caused by tillage of the soil, which results in accelerated oxidation of the carbon in the materials to carbon dioxide gas and its loss to the atmosphere. Following such damages, appropriate soil porosity is regained and maintained chiefly through biotic transformation of the non-living fraction of organic matter by its living fraction - soil-inhabiting fauna and flora - from micro-organisms such as bacteria to macro-organisms such as worms, termites and plants themselves. Their metabolic activity contributes glue-like substances, fungal hyphae etc. to the formation of irregular aggregates of soil particles, within and between which are the all-important pore-spaces in which water, oxygen and carbon dioxide flow and roots grow. These substances also contribute markedly to the soil's capacity to capture and retain nutrient ions on organic complexes, and provide a slow-release mechanism for their liberation back into the moisture in the soil. For this activity and its effects to be maintained, a sufficient supply of new organic matter needs always to be available as a source of energy and nutrients to the soil organisms - not just to the plants alone.

If the conditions are kept favourable for biotic activity in the soil, this dynamic process of formation and reformation of the porous soil architecture will continue from year to year, maintaining the capacities of landscapes thus treated to continue yielding vegetation and water on a recurrent basis, contributing to sustainability of such production processes. Here lies the significance of maintaining 'soil health'. For the purposes of deciding how best to manage the land and nutrients to maintain its productivity, it is more appropriate to think of the soil primarily as a living porous biological entity interpenetrating the non-living components, and forming from the top downwards, rather than as a geological entity forming from the bottom upwards with living things in it at the top (Shaxson et al. 2008).

Managing Biomass Production and Biological Nitrogen Fixation

CA systems require higher levels of biomass production within the rotation to develop and maintain an adequate mulch cover, to raise soil organic matter level, to enhance soil biodiversity and their functions, to raise moisture and nutrient holding capacities, to enhance nutrient supplies, to enrich the soil with nitrogen in the case of legumes, and to protect the soil surface.

Practices that enhance soil organic matter are built into CA principles and include one or more of the following, including: minimal or no-till; diversifying cropping systems; planting trees; mulching; using cover crops and green manures, using crop rotations; and using nitrogen fixing crops.

Nitrogen is fixed from the atmosphere by all kinds of free living organisms in undisturbed soils, and also by rhizobia in root nodules in legume crops as well as in herbaceous and woody legumes. Soil organisms including protozoa and nematodes in the root rhizosphere also fix atmospheric nitrogen, and so the nitrogen cycle has multiple pathways to restore nitrogen to the soil and supply to crops. For crop growth and for soil microorganisms to function, and for soil organic matter to build up, adequate nitrogen supply is needed. No-till and planted fallows and pastures in the rotation can preserve soil integrity and soil organic matter, and various herbaceous and tree legumes can make a contribution to maintaining a positive nitrogen balance for the cropping system (Boddey et al. 2006). Equally, failure to compensate for any net nutrient outputs can lead to losses in soil organic matter and soil nutrient reserves in the short run, and to soil erosion and soil system degradation in the long term.

Farmer and research experience have demonstrated the long-term benefits of a CA system. Research in Canada has shown, that after 20 years of continuous no-till with full stubble retention, higher yields can be obtained compared with a short-term (2-year) no-till system. Major increase in soil organic matter content is assumed to be responsible for these benefits (Derpsch 2007a). The evolution of a long-term CA system is described by Sa (2004) and is quoted by Derspsch 2007a as follows:

"In the initial phase (0-5 years) the soil starts rebuilding aggregates and measurable changes in the carbon content of the soil are not expected. Crop residues are low and nitrogen needs to be added to the system. In the transition phase (5-10 years) an increase in soil density is observed. The amounts of crop residues as well as carbon and phosphorus contents start to increase. In the consolidation phase (10-20 years) higher amounts of crop residues as well as higher carbon contents are achieved, a higher cation exchange capacity and water holding capacity is measured. Greater amount of nutrient cycling is observed. It is only in the maintenance phase (>20 years) that the ideal situation with the maximum benefits for the soil is achieved and less fertilizer is needed."

A constraint that can be critical for many of these biologically-driven innovations is the availability of biomass. We are reminded in Uphoff et al. (2006), that little thought and little investment have been devoted to reducing biomass production and biological nitrogen as a constraint.

Managing Access to a Balanced Nutrient Supply

The more common notion regarding crop nutrition is based on maintaining overall quantities or concentrations of nutrients in the soil. At the practical level, this is reduced to a simple output-input nutrient balance equation so that what is taken out by the crop is or must be replaced by application of nutrients from inorganic fertilizer or other sources. Invariably, this approach is combined with intensive soil tillage that reduces, over time, soil organic matter and porosity, and therefore also its water and nutrient holding capacity as well as all the beneficial soil biological processes.

Neal's Kinsey's book "Hands-on Agronomy" (Kinsey and Walters 2006) clearly shows from direct field experience across many years and many countries, that what is important is that not only is each element necessary individually, but a balance of all soil elements is necessary collectively. If there is too much of a given nutrient, it is going to tie up something else that is needed, e.g. too much potassium ties up boron, too much phosphorus ties up zinc, too much nitrogen ties up copper, too much calcium could tie up all the other nutrients, depending on their availability. Also, imbalances in nutrients can lead to unbalanced plant metabolism making plants vulnerable to all kinds of pathogens as elaborated by Chaboussou (2004).

In a CA system there is no compact subsoil plough layer. Instead there is another type layer, a surface layer of mulch enriched with organic plant residues and nutrients, and altering the dynamics of the organic matter of the soil and the cycling and flows of nutrients (Seguy et al. 2006). In a sense, in CA systems, forest floor conditions are

emulated and nutrient cycling through cover crops act as 'nutrient pumps' to enhance and conserve pools of nutrients from which plant roots feed. Nutrients are returned to the system via mulch mineralization, regulated by C:N ratio and lignin content of the aboveground and root parts of the crops. Much of the system's nutrients are held in the biomass in a semi-closed manner rather than in the soil.

The continuous increase in surface and soil biomass and in soil biological processes in CA facilitate the formation and existence of a nutrient balance as proposed by Kinsey and which leads to crop plants that are healthier. At least 18 mineral nutrients are necessary for plant growth, and maintaining access to a balanced supply of nutrients to crops in CA system is clearly helped by the biologically-oriented processes in the system that has a higher level of biomass and soil organic matter. Organic soil amendments have the advantage of providing more or less a full range of nutrients in contrast to mineral fertilizers. Where there are likely to be serious deficiencies of mineral nutrients, these have to be corrected from the start to avoid disrupting the development of the soil biological processes.

In a fully established CA system the aim of fertilizer nutrient management is to maintain soil nutrient levels, replacing the losses resulting from the nutrients exported by the crops. Because CA systems have diverse crop mix including legumes, and nutrients are stored in the soil organic matter, nutrients and their cycles must be managed more at the system or crop mix level. Thus, fertilization would not anymore be strictly crop specific, with the exception of nitrogen top dressing (if required at all), but will be given to the soil system at the most convenient time during the crop rotation. With the management of legume crops, either as previous crop in the rotation or as component in a cover crop before the next cash crop "top" dressing with nitrogen can be replaced by the N captured by the legumes and released during the following cropping cycle at the required time (more legume content - earlier release, more grass content in cover crop, later release). Additionally, undisturbed soils are habitats for free living nitrogen fixing bacteria and there is rhizospheric fixation of nitrogen (Sprent and Sprent 1990).

Conventional soil analysis data are not necessarily valid as a basis of fertilizer recommendations for CA, since the available soil volume and the mobility of nutrients through soil biological activities tend to be higher than in tillage-based systems against which the existing recommendations have been calibrated. In established CA systems, most nutrients are concentrated and maintained in the top 0-10 cm. For example, phosphorus often identified as a key constraint to crop production, is actually abundant in most soils, with much less that 10% of the total supply "available" at any one time (Uphoff et al. 2006). In CA systems, soils show a higher concentration of available phosphorus in the upper soil layer, and roots will grow right to the soil surface under the mulch. There is much potential for phosphorus solubilization and mobilization through biological processes as influenced by soil moisture changes. Also, the role of mycorrhizas, which are obligate symbioants, in foraging, absorption and translocation to the roots of associated plants of a range of nutrients, and imparting resistances and tolerances against soil pathogens, drought and salinity, aluminum and heavy metals is extensively documented and so is their ability to induce changes in root morphology. Mycorrhiza associations therefore allow larger volume of soil to be exploited for nutrients, particularly those which do not move readily through mass flow or are in relatively immobile form particularly phosphorus, ammonium nitrogen, copper and zinc (Habte 2006). However, micorrhiza diversity and activity is severely curtained by soil tillage and intensive use of agrochemicals, and soil tillage destroys the hyphal networks of micorrhiza fungi thus affecting nutrient mobilization and uptake. Similar to the way rhizobia are linked with leguminous plants, so are symbiotic micorrhizas related to plant nutrition and development in general (Rivera and Fernadez 2006), and these relationships need to be incorporated into nutrient management strategies in CA systems as elaborated in Turner et al. (2006).

Managing Soil Acidity

Soil pH is critical for several reasons. It has a major influence on the availability of elements, including primary nutrients like nitrogen, phosphorus and potassium, as well as secondary nutrients, micronutrients and potentially toxic elements like aluminum. Most soil microorganisms are sensitive to soil acidity, which has an influence on nutrient availability (especially nitrogen), soil organic matter and general soil health. The most beneficial soil fungi, for instance, do not like a high pH, and soil bacteria have problems at lower pH. One of the main reasons for managing soil pH by application of lime is to reduce such toxic effects. However, soil acidity becomes self-adjusting at 6.2 or 6.3 when all four cations — calcium, magnesium, potassium and sodium — are in proper equilibrium (Kinsey and Walters 2006). Any one of them in excess can push pH up, and any one of them in lower amounts can take pH down.

CA systems are based on building and breaking down organic matter to maintain soil health and productivity. As microorganisms decompose soil organic matter, organic acids are continuously being formed. If these acids are not neutralized by free bases, then soil acidity will increase. There are other reasons why soil can be acidic, due to leaching of basic cations by rainfall, or to soil being formed from acid parent materials, or to biological nitrogen fixation. Where soils are acidic particularly in humid and sub-humid soils and may have toxic levels of aluminum, the effectiveness of broadcast lime application without incorporation has been long proven in CA systems, as lime moves into deeper soil layers, especially when applied in small quantities each year in combination with green manure cover crops (Derpsch 2007b). Experience Brazil shows that aluminum toxicity tends to disappear over time under CA systems.

Towards CA-Based Nutrient Management Practices

Integrated Soil Fertility Management (ISFM) and Integrated Natural resources Management (INRM) approaches of various types and nomenclature have been in vogue in recent years in certain sections of the scientific community. Generally, such approaches are focused more on meeting crop nutrient needs rather than managing soil health and land productivity as is the case with CA systems. Also, most of the work that is couched under the rubric of ISFM or INRM over the past 15 years or so has been geared towards tillage-based systems which have many unsustainable elements, regardless of farm size or the level of agricultural development. Unless the concepts of soil health and function are explicitly incorporated into ISFM or INRM approaches, sustainability goals and means will remain only accidentally connected, and sustainable crop intensification will be difficult to achieve particularly by resource poor farmers.

We believe that CA systems have within them their own particular sets of ISFM or INRM processes and concepts that combine and optimize the use of organic with inorganic inputs integrating temporal and spatial dimensions with soil, nutrient, water, soil biota, biomass dimension, all geared to enhancing crop and system outputs and productivities but in environmentally responsible manner. There is empirical evidence to show that CA-based ISFM or INRM processes can work because of the underpinnings of soil health and function.

Focusing on soil fertility but without defining the tillage and cropping system, as often proposed by ISFM or INRM approaches, is only a partial answer to enhancing and maintaining soil health and productivity in support of sustainable production intensification, livelihood and the environment. Over the past two decades or so, empirical evidence from the field has clearly shown that healthy agricultural soils constitute biologically active soil systems within landscapes in which both the soil resources and the landscape must operate with plants in an integrated manner to support the various desired goods and services (e.g., food, feed, feedstock, biological raw material for industry, livelihood, environmental services, etc) provided by agricultural land use.

Consequently, successful nutrient management strategies as part of any ISFM or INRM approach must pay close attention to issues of soil health management which means managing the microscopic integrity of the soil-plant system particularly as mediated by soil living biota, soil organic matter, soil physico-chemical properties, available soil nutrients, adapted germplasm as well as to managing the macroscopic dimensions of landscapes, socioeconomics and policy. Given that CA principles and practices offer substantial benefits to all types of farmers in most agro-ecological and socio-economic situations, CA-based IFSM and INRM approaches to nutrient management and production intensification would be more effective for farmer-based innovation systems and learning processes such as those promoted through Farmer Field School networks.

Adopting a CA-Based Nutrient Management Framework

CA has now emerged as a major "breakthrough" systems approach to crop and agriculture production with its change in paradigm that challenges the status quo. However, as a multi-principled concept, CA translates into knowledge-intensive practices whose exact form and adoption requires that farmers become intellectually engaged in the testing, learning and fine tuning possible practices to meet their specific ecological and socio-economic conditions (Friedrich and Kassam 2009).

In essence, CA approach represents a highly biologically and biogeophysically-integrated system of soil health and nutrient management for production that generates a high level of "internal" ecosystem services which reduces the levels of "external" subsidies and inputs needed. CA provides the means to work with natural ecological processes

to harness greater biological productivities by combining the potentials of the endogenous biological processes with those of exogenous inputs. The evidence for the universal applicability of CA principles is now available across a range of ecologies and socio-economic situations covering large and small farm sizes worldwide, including resource poor farmers (Goddard et al. 2007, FAO 2008).

There are many different ecological and socio-economic starting situations in which CA has been and is being introduced. They all impose their particular constraints as to how fast the transformation towards CA systems can occur. In the seasonally dry tropical and sub-tropical ecologies, particularly with resource poor small farmer in drought prone zones, CA systems will take longer to establish, and step-wise approaches to the introduction of CA practices seem to show promise (Mazvimavi and Twomlow 2006). These involve two components: the application of planting 'Zai-type' basins which concentrate limited nutrients and water resources to the plant, and the precision application of small or micro doses of nitrogen-based fertilizer. In the case of degraded land in wet or dry ecologies, special soil amendments and nutrient management practices are required to establish the initial conditions for soil health improvement and efficient nutrient management for agricultural production (Landers 2007). What seems to be important is that whichever pathway is followed to introduce CA practices, there is a need for a clear understanding of how the production systems concerned should operate as CA systems to sustain soil health and productivity, and how nutrient management interventions that may be proposed can contribute to the system effectiveness as a whole both in the short- and long-term.

Concluding Remarks

Many of the CA related soil processes, e.g. increased soil organic matter content and soil porosity, or increased biological nitrogen fixation by legumes in rotation, or exploitation of the deeper soil layers through crops with deep and dense root systems, have a significant bearing on nutrient management. Evidence shows that in CA systems, nutrient requirements are lower, nutrient efficiencies are higher and risks of polluting water systems with mineral nutrients lower.

However, systematic research into CA systems and their nutrient management requirements are of relatively recent origin as can be seen from the research work reported in Uphoff et al. (2006) or in the Goddard et al. (2007) compendium. Both these volumes imply that nutrients as a production input are a necessary condition but not a sufficient condition for sustainable production intensification. In CA systems, the focus is on managing soil health and productivity simultaneously and which depends on many complex cropping system relationships in space and time and on biodiversity and organic matter within soil systems when they are enlisted on behalf of agricultural production.

Ultimately, the management of nutrient input-output relationships in CA systems must balance the nutrient accounts which means that the levels of outputs of biological products that are aimed at will dictate the levels of inputs, and ongoing nutrient balances must remain positive. The major difference with CA systems is that the management of the multiple sources of nutrients and the processes by which they are acquired, stored and made available to crops are more biologically mediated. Much more research needs to be done on the different aspects of soil health and nutrient management in CA-system as is now beginning to occur as more countries begin to adopt and integrate CA concepts and practices into commercial production activities at both small and large scale as a basis for future sustainable production intensification strategies.

As an appropriate ending to this paper we would like to quote Derpsch 2007b:

"Experience has shown that most things learned at university about fertilization and liming should be revised, and new concepts of fertility management for no-till systems need to be developed and applied. The main principle to keep in mind is that farmers should fertilize their soils rather than their crops."

References

Boddey, R.M., Bruno, J. R. A. and Segundp, U. 2006. Leguminous biological nitrogen fixation in sustainable tropical agroecosystems. In: Biological Approaches to Sustainable Soil Systems (Uphoff, N. et al., Eds.), pp 401-408. CRC Press, Taylor & Francis Group.

Chaboussou, F. (2004). Healthy Crops: A New Agricultural Revolution. Jon Carpenter Publishing. 244 pp.

Derpsch, R. 2007a. No-tillage and Conservation Agriculture: A Progress Report. In: No-Till Farming Systems (Goddard, T. et al., Eds.), pp. 7-39. WASWC Special Publication No. 3, Bangkok.

Derpsch. R. 2007b. Critical Steps in No-till Adoption. In: No-Till Farming Systems (Goddard, T. etal., Eds.), pp. 479-495. WASWC Special Publication No. 3, Bangkok.

FAO, 2008. Investing in Sustainable Agricultural Intensification: The Role of Conservation Agriculture - A Framework for Action' FAO Rome, August 2008 (available at www.fao.org/ag/ca/).

Friedrich, T. and Kassam, A.H. 2009. Adoption of Conservation Agriculture Technologies: Constraints and Opportunities. Invited paper, IV World Congress on Conservation Agriculture, 4-7 February 2009, New Delhi, India.

Goddard, T., Zoebisch, M., Gan, Y., Ellis, W., Watson, A. And Sombatpanit, S. (2007) (Eds.). No-Till Farming Systems. WASWC Special Publication No. 3, Bangkok, 544 pp.

Habte, M. 2006. The Roles of Abuscular Mycorrihizas in Plant and Soil Health. In: Biological Approaches to Sustainable Soil Systems. (Uphoff, N. et al. Eds.), pp. 131-147. CRC Press, Taylor & Francis Group.

Kinsey, N. and Walters, C. 2006. Neal Kinsey's Hands-On Agronomy: Undersatnding Soil Fertility & Fertilzer Use. Acres USA. 391 pp.

Landers, J. 2007. Tropical Crop-Livestock Systems in Conservation Agriculture: The Brazilian Experience. Integrated Crop Management Vol. 5. FAO, Rome.

Mazvimavi, K. and Twomlow, S. 2006. Conservation Farming for Agricultural Relief and Development in Zimbabwe. In: No-Till Farming Systems (Goddard, T. et al., Eds.), pp. 169-175. WASWC Special Publication No. 3, Bangkok.

Rivera, R. and Fernadez, F. 2006. Innoculation and Management of Mycorrhizal Fungi within Tropical Agroecosystems. In: Biological Approaches to Sustainable Soil Systems (Uphoff, N. et al., Eds.), pp 479-489. CRC Press, Taylor & Francis Group.

Sanchez, P.A. 1994. Tropical soil fertility research: towards the second paradigm. In: Transactions of the 15th World Congress of Soil Science, Acapulco, Mexico, pp. 65-88. Mexican Soil Science Society, Chapingo, Mexico.

Seguy, L., Bouzinac, S. and Husson, O. 2006. Direct-seeded Tropical Soil Systems with Permanent Soil Cover: Learning from Brazilian Experience. In: Biological Approaches to Sustainable Soil Systems (Uphoff, N. et al., Eds.), pp 323-342. CRC Press, Taylor & Francis Group.

Shaxson, F., Kassam, A.H., Friedrich, T., Boddey, B. and Adekunle, A. 2008. Underpinning Conservation Agriculture's Benefits: The Roots of Soil Health and Function. Main background document for the Workshop on Investing in Sustainable Crop Intensification: The Case for Improving Soil Health, 22-24 July, FAO, Rome.

Sprent, J. I. and Sprent, P. 1990. Nitrogen Fixing Organisms: Pure and Applied Aspects. Chapman and Hall Ltd. 272 pp.

Turner, Benjumin L., Frossard, Emmanual and Oberson, Astrid (2006) Enhancing Phosphorus Availability in Low-fertilty Soils. In: Biological Approaches to Sustainable Soil Systems (Uphoff, N. et al., Eds.), pp 191-205. CRC Press, Taylor & Francis Group.

Uphoff, N., Ball, A.s., Fernandes, E., Herren, H., Husson, O., Laing, M., Palm, C., Pretty, J., Sanchez, P., Sanginga, N., and Thies, J. (2006) (Eds.). Biological Approaches to Sustainable Soil Systems. CRC Press, Taylor & Francis Group. 764 pp.

Opportunities and Challenges for Water and Nutrient Management in Conservation Agriculture Farming Systems of Asia and Africa

Christian H Roth1, Merv Probert2, Jack McHugh3 and Greg Hamilton4

1 Australian Centre for International Agricultural Research ACIAR, Canberra, Australia, roth@aciar.gov.au; 2

CSIRO Sustainable Ecosystems, Brisbane, Australia, merv.probert@csiro.au; 3 University of Southern Queensland, Toowoomba, Australia, mchugha@usq.edu.au; 4 Department of Agriculture and Food Western

Australia, Perth, Australia, ghamilton@agric.wa.gov.au

Building on the positive experiences in Brazil, Australia and the USA, over the past decades conservation agriculture (CA) has seen increasing acceptance by farmers in Asia, and to a lesser extent in Africa. Research in these evolving systems has generated a considerable amount of data and knowledge about the contribution of CA to increased water and nutrient use efficiency. In order to more systematically evaluate how effective the different CA systems in Asia and Africa are in reducing input requirements we propose a framework to broadly categorise the main types of CA systems, before we take a water and nutrient balance approach to discuss the performance of these systems with respect to key water and nutrient (mainly N) fluxes. The outcome of this analysis is that while there are major opportunities for a range of CA systems to increase water and nutrient input efficiencies, there are also some long term environmental risks. In addition, we argue that there is a discrepancy between a large proportion of the body of work and the theoretical benefits in water and nutrient savings on the one hand, and the reality on the ground on the other hand.

We attempt to illustrate this in greater depth by presenting the results of two case studies. One study looks at the role of residue retention in the long-term evolution of organic matter in no-tillage systems for a range of semi-arid rainfed soil and climate conditions. Using a cropping systems modeling approach, we demonstrate that there are significant interactions between water and nutrients that determine whether CA in these conditions will or will not contribute positively to soil health and crop productivity as well as water and nutrient use efficiency. Importantly, failure to recognize that most semi-arid systems are in fact low-input, mixed crop-livestock systems with low levels of residue retention, can lead to an overestimation of organic matter build-up and water and nutrient efficiencies to be gained from CA in these farming systems.

In the second case study we investigate irrigated, permanent raised bed maize-wheat systems in Pakistan and China. We demonstrate that measured and modeled savings in irrigation water can potentially lead to salt accumulation in the beds. Managing the salt build-up is relatively straight forward, but requires maintaining higher leaching fractions, at the expense of the water savings and with the risk of higher N leaching rates. This in turn diminishes the perceived benefits of CA in these conditions.

Polymicrobial Formulations for Enhanced Productivity of a Broad

Spectrum of Crops

C.A. Reddy* and J.Lalithakumari

Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824-4340, USA (*Email: reddy@msu.edu)

Our principal aim in this research is to develop stable, efficacious, and eco-friendly microbial formulations containing naturally occurring diverse phylogenetic groups of microbes with complementary functions designed to enhance productivity of a broad spectrum of crops. The formulation is designed to provide the observed beneficial effects through enhancement of nitrogen fixation, direct or indirect inhibition of plant pathogens, solubilization and mobilization of minerals such as P, and production of plant growth stimulants. We constructed two such formulations (F1 and F2) using humate (12%, ph 7.0) as a carrier. F2 formulation was found to be more effective than F1 in enhancing the productivity of a broad spectrum of crops and was the focus of this study. Substantial increase in productivity was observed with the following crops: Zea mays (corn), Sorghum bicolor (sorghum), Glycine max (soybean), Phaseolus vulgaris (Garden bean), Pisum sativum (pea), Phaseolus sp. (wonder bush bean), Arachis hypogea (peanut), Oryza sativa (rice), Lycopersicon esculentum (tomato), Solanum melongena (eggplant), Hibiscus esculentus (okra), and Cucurbita maxima (squash). For example, when compared to controls, corn height increased by 65%, eggplant 41%; wonder bush beans 40%, tomato 91%, soybeans 96%, pea purple hull 50%, and okra 16%. Significant increase in yield was also observed. For example, mean yield of tomato increased by 88%, okra yield increased by 50%, and rice yield by 40%. In general, the F2-treated plants appeared healthier and showed early flowering and fruiting with good root nodulation in legumes. Yields obtained in field trials were consistent with those from the greenhouse experiments. The results indicate that polymicrobial formulations such as F2 reduce input for nitrogen fertilizers and pesticides, enhance productivity of a broad spectrum of crops, non-polluting, and contribute to the conservation of soil health.

Key words: Microbial formulation, enhanced crop production, polymicrobial, nitrogen fixation, phosphate mobilization, biological control

Facing a steep rise in the price of energy, a growing concern over global warming, and a quickly growing world human population (estimated at 6.9 billions in 2010), the need has never been greater for an increase to crop productivity on a long-term, sustainable basis in an energy efficient and eco-friendly manner (Triplett et al. 2007). Therefore, the working hypothesis is that it is possible to develop stable, efficacious, and ecofriendly microbial formulations containing diverse groups of microbes with complementary functions designed to enhance productivity of a broad spectrum of plants including legumes, non-legumes, vegetables, cereals, ornamentals, and fodder crops with little or no input of nitrogen fertilizers and chemical pesticides. The formulations are expected to provide the observed beneficial effects by multiple mechanisms including but not limited to the following: enhancement of nitrogen fixation; control of plant pathogens either directly or indirectly by inducing systemic resistance in plants against the pathogens; solubilization and mobilization of minerals such as P and others; and production of growth stimulants. While the idea of microbial inoculants for stimulating crop production is not new, careful and deliberate design of a formulation to contain multiple naturally occurring phylogenetic groups of organisms with complementary functionalities and putting them together in a manner that they retain viability over a long period of time at ambient temperature and with little or no need for added chemical fertilizers and pesticides is innovative.

Symbiotic N2-fixing bacteria such as Rhizobiales (associated with leguminous crops) and free-living N2-fixing bacteria such as the Azospirillum group (associated with the roots of cereal crops such as rice, wheat and corn, and certain forage grasses) account for a major portion of biological nitrogen fixation on earth (Bashan et al.2004;; O'Hara et al., 2003; Rai, 2006; Xavier et al. 2004). These beneficial bacteria decrease the need for added nitrogen fertilizers for crop production, contribute to conservation of fossil fuel energy resources that are currently used for manufacturing N-fertilizers, and help reduce pollution and public health problems associated with the high use of chemical fertilizers. Other free-living microbes that contribute to N2-fixation in soils include: Acetobacter and Herbaspirillum strains associated with sugarcane, sorghum and maize (Balachandar et al., 2007; Boddey et al., 2000) and Alcaligenes, Bacillus, Enterobacter, Klebsiella and Pseudomonas strains associated with a range of crops such as rice and maize (Somasegaran and Hoben, 1994). Moreover, rhizosphere bacteria such as Paenibacillus, Burkholderia, and (a-, a-, a-) proteobacteria were reported to give 'positive plant growth response attributed to their ability to fix N2 and/or their ability to produce secondary metabolites and phytohormones (Polianskaia et al., 2003; Petersen et al., 1996; Rai, 2006; Rudresh et al., 2005.). Phosphate-solubilizing bacteria (PSB) such as Pseudomonas,

Bacillus, Azospirillum, Rhizobium, Alkaligenes, Paenibacillus, and Penicillium digitatum contribute to plant growth by producing organic acids and make insoluble P compounds soluble for uptake by the plant (Sundara et al. 2002; Rodriguez and Fraga, 1999).

An array of pesticides belonging to different chemical classes is used for controlling a variety of plant diseases. A number of pesticides are recalcitrant to degradation, persist in the environment, and enter the human/animal food chain constituting a threat to public health and a potential hazard to the environment. Some are toxic to humans even at parts per billion levels. Therefore, there is increasing public concern regarding the continued use of chemical pesticides at high levels and there is a growing need for developing environmentally friendly approaches to control common plant diseases and contribute to the goal of sustainability in agricultural production. In this regard, there is much ongoing research on bio-control agents (bio-pesticides) for inhibiting pathogenic fungi, bacteria, and even nematodes and small insects that cause crop losses. Soil-borne, non-pathogenic bacteria and fungi that are able to control different plant pathogens are attractive alternatives to the use of chemical pesticides. A number of bacteria and fungi that serve as biological control agents (BCAs) as well as plant growth-promoting rhizobacteria (PGPR) are catabolically versatile, have excellent root-colonizing abilities, and have the capacity to produce a wide range of metabolites that act against plant pathogens. Soil-borne fluorescent pseudomonads have received particular attention. Some of these have been shown to elicit induced systemic resistance in plants. Strains of Bacillus subtilis are known to suppress soil-borne fungal diseases and nematodes, produce metabolites that stimulate plant and root growth, and colonize the root zone resulting in exclusion of some of the pathogens by 'competitive exclusion' (Walsh et al., 2001) .

Trichoderma are free living and fast growing fungi in soil and root ecosystems of many plants. Trichoderma have been demonstrated to inhibit a broad spectrum of root and foliar pathogens by one or more of the following mechanisms (Harman et al. 2004; Mathivanan et al. 2000; Carver et al. 1996): antibiosis, antagonism, and competitive exclusion. Furthermore, Pseudomonas and Trichoderma species that function as bio-control agents do not inhibit nitrogen fixers, arbuscular mycorrhizal fungi, and other beneficial microbes that positively impact plant growth (Walsh et al. 2001; Rudresh et al. 2005)Mathivanan et al. 2000). Trichoderma species have also been reported to serve as plant growth promoters by producing phytohormones and solubilize/mobilize phosphates (Yedidia et al.2001).

There is much published information on the benefit of individual microbes to plants (Xavier et al. 2004; Somasegaran and Hoben, 1994; Kannaiyan, 2000), but there is hardly any commercial product that is capable of conferring all the beneficial effects on crop productivity mentioned above. Our overall objective in this study was to construct a microbial formulation containing multiple groups of functionally complementary microbes (bacteria and fungi) that hold promise in enhancing productivity of a broad spectrum of plants including legumes, cereals, vegetables, and forage crops. Many of the commercial microbial inoculants have not lived up to their claims in that Brockwell and Bottomley (1995) reported that 90% of all inoculants have no practical value whatsoever on the productivity of legumes. A desirable microbial growth promotant should have good efficacy, ease of application, eco-friendly, stable, and safe for use. Furthermore, rhizobial species in the inoculant must be able to nodulate diverse legumes under various soil and environmental conditions.

Results

Construction of Polymicrobial Formulations

The research presented here highlights a rational approach to the use of diverse groups of organisms with complementary functionalities to confer multiple beneficial effects on growth and yield of a broad spectrum of crops. As a first step, numerically predominant bacteria from the root nodules of various leguminous plants as well as from soil and rhizosphere samples collected from diverse environmental sources were isolated and characterized. Dominant rhizobial as well as the non-rhizobial species were isolated from the root nodules of pea, cow pea (Vigna sinensis), green gram (V radiata), black gram (V mungo), red gram (Cajanus cajan), soybean, and agati (Sesbania grandiflora) collected from temperate and tropical regions using established procedures (Hung et al. 2005; Kannaiyan, 2000; O'Hara et al. 2003; Pandey et al., 2004). The microbial isolates were identified based on morphological, physiological and biochemical characteristics as well as their 16S rDNA sequencing data. Functional characteristics such as nitrogen fixation, phosphate solubilization/mobilization, root nodulation using different leguminous plants, and growth under acidic and alkaline conditions were used in further grouping of the isolates. Isolates were also characterized as to their saprophytic competence (Weaver and Frederick, 1972). Similarly, a large number of bacteria isolated from various soils were isolated and identified and key functional characteristics were determined.

A number of Trichoderma species isolated from different soil samples (representing cultivated and uncultivated agriculture soils, tropical, subtropical, and temperate climates) because of their reported beneficial effect in positively influencing productivity of different crops. Individual strains were isolated using single spore isolation technique using plates of potato dextrose agar. Identification was based on macro-microscopic features, colony color, and rate of growth, using standard procedures (Sariah et al. 2005). Trichoderma isolates were then screened for their potential as biocontrol agents against known plant pathogenic fungi such as Alternaria alternata and Curvularia Sp., Bipolaris oryzae, Magnoporthe grisea, Rhizoctonia solani using dual plate technique (Carver et al. 1996). Also, all the Trichoderma strains were tested for their saprophytic competence in soil.

Species representing several genera of Rhizobiales, several root-nodulating non-rhizobial species (consisting of both a-, b-, and g- proteobacteria), a number of phosphate solubilizing bacteria, microbes (both bacteria and fungi) with proven ability as biocontrol agents, and other beneficial bacterial species with growth-promoting properties were used in constructing two bacterial formulations F1 and F2 using 12% humate as the base. The microbial species composition of F1 and F2 was different but each contained over 20 different microbial strains representing selected combinations of bacteria and Trichoderma strains with the beneficial characteristics mentioned above.

The PCR amplification and sequencing of 16S rDNA of the isolates revealed both nodulating Rhizobia such as Ensifer meliloti (Rhizobium meliloti; Sinorhizobium meliloti), R. trifoli, as well as Azorhizobium caulinodans, Sinorhizobium fredii, and non-Rhizobial nitrogen fixers including Pseudomonas spp., Burkholderia spp, and Paenibacillus polymyxa. Other bacterial isolates included in the formulations were Pseudomonas fluorescens, P. striata, and Bacillus subtilis representing multiple functions such as phosphate solubilization/mobilization, nutrient uptake, and phytohormone production. Nodulation experiments confirmed the nodulating ability of bacteria in the polymicrobial formulation (Fig. 1). Trichoderma isolates included strains of: T. harzianum, T. viride, T. virens, and T. longibra chia turn.

Figure 1. Nodulation observed on roots of garden bean grown in the presence of polymicrobial formulation, F2

Green House Evaluation

Baccto premium potting soil (Michigan peat Company, Houston, TX) was used for growing the selected test plants in the greenhouse experiments. A randomized replicated design was used to set up growth experiments for testing the efficacy of F1 and F2 formulations. For each 12"X12"X12" pot, two split applications of the liquid formulations (1010 cfu per pot) were given during the crop period. The first application was given as soil treatment at the time of sowing and the second application was given at the base of the plant one month after the first application. The experiments were set up in such a way to compare the efficacy of F1 and F2 formulations in comparison to a control (HG) containing 12% humic acid alone without any added microbes. Hence, 3 treatments, i.e. F1, F2, and control (HG), each with 4 replications were tested. Exogenous fertilizers or pesticides were not added to any of the three treatments during the crop period. Most inoculant standards contain a minimum number of viable microbial cells of at least 109rhizobia /gram soil (Brockwell and Bottomley, 1995; Xavier et al. 2004). Plant minerals (minus N) was added to each treatment 15 days after germination. A broad spectrum of crops which includes cereals,

vegetable crops, legumes, forage grasses and also biofuel grasses were tested. Plants including garden beans, wonder bush beans, purple hull beans, pea, cowpea, green gram, black gram, soybean, tomato, eggplant, okra, squash, zucchini (Cucurbita pepo), corn, sorghum, rice, and peanut were tested to compare the efficacy of F1 and F2 in enhancing productivity. Observations were made at monthly intervals during the entire crop period. In a separate experiment, the efficacy of F1 and F2 on germination and growth of commercially available forage legumes seed mixture (Tecomate Monster Seed Mix, Todd Valley Farms, Nebraska) was tested. Plant height, total number of leaves, leaf area, leaf color, flowering time, fruiting time, shoot and root biomass, and the incidence of pests and diseases were monitored.

The results (Table 1, Fig. 2 to 5) showed a significant increase in plant height with F2 treatment followed by F1 and control. For example, when compared to controls, corn height increased by 65%; egg plant 41%; wonder bush beans 40%; tomato 91%, soybeans 96%, pea purple hull 50%, and okra by 16%. Yield also significantly increased in F2 treatment. For example, mean yield of tomato increased by 88% as compared to the control. Okra yield increased 50% and rice increased by 40%. With rice, both F1 and F2 showed an increase in seedling vigor, plant height, number of tillers and their carry over effect on grain yield. All legumes tested showed early flowering and fruiting, good root nodulation, and no disease was observed in both the experimental and control plants during the crop period. (results not shown).

Table 1. Green House evaluation of polymicrobial formulations F1, F2, and control (C)

Crop Plant Height [cm] Yield [g]

F2 F1 C F2 F1 C

Corn 142 125 101.2 - - -

Sorghum 74 68.5 49 - - -

Rice 65 60 55 20.85 15.76 5.2

Tomato 77 72 66 1900* 755* 380

Soybeans 167.7 160.5 98 11.58* 7.9 5.1

Pea 45 38 33 13.99* 10.48* 7.52

Okra 130 93.7 98 138.7* 100* 38.7

Peanut 42 42 35 21.62* 14.67* 6.48

Pea purple hull 60.96 46.48 40.64 14.75* 12.23* 10.75

Garden beans 135 128 102 48.6* 42.6* 23.5

Wonder bush beans 88.9 76.2 63.5 72.9* 63.6 35.6

Squash 57 41 36 650* 230* 0

'Significant, P = 0.022

ïeptiipi -yum

u —^m--M

n FI c

|j| 11 31 JD 3.1

Tn aim i nl

Figure 2. Plant height (2a) and yield (2b) of soybean grown in the presence of polymicrobial formulations F1 and F2

as compared to a control with no formulation added

There is a significant commercial interest in products that substantially increase productivity of forage crops. The present results further confirm that F2 formulation enhances the growth of a commercial seed mixture of forage crops called Tecomate Monster Mix, as compared to humate alone as control (Fig. 6)

Figure 3. Plant height (3a) and yield (3b) of rice grown in the presence of polymicrobial formulations F1and F2 as

compared to a control with no formulation added

Figure 4. lant height (4a) and yield (4b) of tomato grown in the presence of polymicrobialformulations F1and F2 as

compared to a control with no formulation added

Figure 5. Plant height (5a) and yield (5b) of wonder bush beans grown in the presence of polymicrobial formulations Fland F2 as compared to a control with no formulation added

Field Evaluation

Field trials were conducted with the cooperation of BioSoil Enhancers (Hattiesburg, Mississippi) to test the efficacy of the polymicrobial formulations on soybean, corn, cotton, yellow squash, tomato, green beans, bell pepper (Capsicum annuum) and banana pepper (Capsicum spp.). The yield data obtained in field trials were

Figure 6. Growth observed with a commercial forage seed mixture (Tecomate Monster Mix) in the presence of formulation F2 (right) and control (left)

consistent with results of green house experiments in showing a distinct increase in yield of all the crops tested. For example, crops treated with polymicrobial formulation F2 showed 75% increase in yield for tomatoes; 27% for bell peppers; 40% for banana peppers; and 61% for yellow squash (Table 2). Increase in corn yield was 30.0% and cotton plants treated with the polymicrobial formulation also showed increased plant height, good branching, and large sized healthy bolls when compared to control (results not shown). Both green house and field trials indicate that appropriately formulated polymicrobial formulations have excellent potential to enhance productivity of a broad spectrum of crops. Moreover, the need for nitrogen fertilizers and pesticides greatly decreased, which substantially contribute to the conservation of soil health, and conservation of fossil fuel energy sources. Further research progress in this area would be a substantial contribution to boosting crop production compatible with sustainable agriculture practices.

Table 2. Field evaluation of polymicrobial formulations

Crops F2 formulation F1 formulation Contro F2 - % increase in

(oz) (oz) (oz) yield over control

Squash 1559 1414 963 61

Tomato 836 514 477 75

Banana Pepper 35 15 25 40

Bell Pepper 102 87 80 27

Discussion

The results showed much better growth with F2 in terms of increased plant height, total number of leaves and total biomass of tested crops. It was expected that leguminous plants which support symbiotic nitrogen fixation such as soybean, garden bean, wonder bush bean, pea and other legumes would give better performance with F2 formulation as it contains symbiotic nitrogen fixers, as well as some free-living nitrogen fixers, and biocontrol agents. However, it is noteworthy that even non-leguminous plants such as tomato, eggplant, zucchini, squash, rice, corn, and sorghum, which are not associated with symbiotic nitrogen fixation, showed impressive growth response. These results suggest that free-living N2 fixers, biocontrol agents, and organisms that produce nonspecific growth stimulating compounds in the formulations are contributing to the observed positive growth response. These results appear to validate our hypothesis that enhanced plant growth and productivity can be obtained with a broad spectrum of plants when grown with microbial formulations containing microbes representing several different complementary functional groups. It is also remarkable that the growth response with rice and corn, two of the most important food crops worldwide, was quite encouraging suggesting that either non-N2 fixers that give a growth response by producing metabolites/micronutrients that boost plant growth or hither to not well characterized nonconventional N2-fixers (Balachandar et al. 2007) may be contributing to the observed positive growth response. For example it has earlier been reported that association of Pseudomonas sp. and Trichoderma sp. with cereal crops such as rice will result in increased productivity (Rudresh et al. 2005). Pseudomonads and Trichoderma not

only act as biocontrol agents but also produce metabolites that enhance plant growth (Yedidia et al 2001). Furthermore, Yanni et al (1997) report that Rhizobium leguminosarum bv. trifolii shows endophytic association with rice and increase productivity of the latter. It is also possible that other free living N2-fixers such as Paenibacillus and Burkholderia may be contributing in part by providing fixed nitrogen to the plant (Balachandar et al.2007). In addition to nitrogen, phosphorous made available by phosphate-solubilizing bacteria may also be contributing to increased growth of cereals (Sundara et al. 2002). These possibilities need to be tested in future. The results presented above further suggest that other non-nitrogen fixing microbes in our formulations are able to confer substantial boost in productivity.

Conclusions

To the best of our knowledge there is no microbial formulation on the market today that is specifically designed to contain a comprehensive set of microbial groups with multiple complementary functions and with documented efficacy for substantially increasing productivity of such a broad spectrum of important pulses, cereals, vegetable, and forage crops as reported here. Heavy use of chemical fertilizers and pesticides that are often employed for increasing crop productivity now result in leaching of nitrates which at high levels pose a health hazard to humans. Further more, when soils become anaerobic, nitrate (NO3) is reduced to nitrous oxide N2O, which is over 300 times more potent than CO2 as a greenhouse gas. Polymicrobial formulations decrease the need for nitrogenous fertilizers (by almost 50%) and pesticides. Therefore, polymicrobial formulations similar to F2 (or even more improved future products) have the potential to greatly increase crop productivity with less dependence on chemical fertilizers and pesticides, greatly reduce the cost of cultivation, and alleviate negative health and environmental consequences associated with the use of the latter compounds. Polymicrobial formulations also help solubilize key plant nutrients such as phosphate and make it more available for uptake by the plant. Moreover, products such as F2, consisting of microbes that naturally occur in nature, are eco-friendly, conserve soil health in increasing the number of bacteria beneficial to crop productivity, ensure better utilization of our natural resources, and are highly compatible with sustainable agricultural practices.

Acknowledgements

We acknowledge partial support from the Michigan Agriculture Experiment Station and from BioSoil Enhancement Inc. We acknowledge Poorna Viswanathan for her help with the 16S rDNA analyses.

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Developing Alternate Tillage and Crop Establishment Strategies for Higher Resource Use Efficiencies in the Rice-Wheat System

J.K. Ladha*

Rice-Wheat Consortium and International Rice Research Institute-India

The rice-wheat cropping systems of the Indo-Gangetic Plains (IGP) are of immense importance for food security for south Asia. However, yield stagnation/decline; water and labour scarcity; and soil, water, and air pollution are the emerging threats to the sustainability of rice-wheat systems. Therefore, the design and implementation of alternative production systems with increased resource use efficiency, profitability and productivity, and reduced adverse environmental impact, are urgently required. One of the strategies to address emerging problems, specifically shortages of water and labour, is to grow rice and wheat on zero or reduced-till land through drill with precision water management. The shift from puddled-transplanted rice on the flat land to raised bed systems affects the productivity and resource use efficiency of the rice-wheat system. Therefore, the potential benefits and constraints of alternative tillage and crop establishment systems need to be quantified on short to long-term basis and optimum layouts and management systems need to be identified to maximize yield and input use efficiency. To answer above questions, numerous farmer participatory trials on various tillage and crop establishment practices were conducted in Bangladesh, India, Nepal and Pakistan during last four years. On-farm data were analyzed using SAS Mixed Unbalanced Model and SAS Macro procedures. In addition, an on-station experiment was conducted for six years to collect detailed long-term data on productivity, resource use efficiency, partial budgeting and global warming potential. Various practices had highly variable responses. However a general trend emerged that crop productivity may or may not have positive response but resource use efficiency and farmers income tend to be superior with several alternate tillage and crop establishment strategies. This paper will analyze the reasons of variable technology response function to develop strategies for improvement and widespread delivery.

* with contribution from Alam M, Chandra P, Gathala M, Gupta RK, Kumar V, Pathak H, Prasad R, Raman A, Regmi AP, Rehman H, Saharawat Y, Sharma S, Singh UP.

Session 1.3: Diversified Farming Systems

Lessons Learned from the Extension of Direct Seeding, Mulch-Based Cropping Systems (DMC) in the Main Agro Ecological Zones of

Madagascar

Rakotondramanana, O. Husson and A. Rakotondralambo

Executive Director, GSDM lot VA 26 Y Ambatoroka, ANTANANARIVO (101) (Madagascar: gsdm.de@moov.mg) 2CIRAD/GSDM, GSDM lot VA 26 Y Ambatoroka, ANTANANARIVO (101) (Madagascar: olivier.husson@cirad.fr) 3Chairman of the Board, GSDM, DG ANAE, Lot II Y 39A bis, Ampasanimalo, BP 5092, ANTANANARIVO (101 (Madagascar: aralambo@netclub.mg)

Extension of Direct Seeding Mulch-based cropping systems (DMC) among small scale farmers have been tested in the main agro ecological zones of Madagascar for a period of up to 7 years. These agro ecological zones include climates ranging from subtropical climate at sea level to sub-tropical and semi-temperate climates at high altitude. Four main agro ecological zones were identified: (i) the eastern coast of the Country at sea level with high rainfall (1500 to 2500 mm/year) and high temperature, (ii) the medium altitude (800 to 900 m asl) of the Alaotra Lake and the Middle West, with 6 to 7 months of dry seasons and medium rainfall (600 to 1200 mm/year), (iii) the high altitude areas (1000 m to 1500 m asl) with a 6- months long rainy season (1200-1500 mm/year) and a 6-months long dry and cold season, and occurrence of frost in some areas and (iv) the dry area of the South of the Country with 3 to 4 months of rains (300 to 600 mm/year). The extension was decided after more than 10 years of adaptation of DMC systems by the NGO TAFA in the same areas and training of key field extensionists and group of farmers. Reference sites testing different systems compared with conventional tillage are maintained in these areas and are being used for training of all stakeholders. The GSDM which is a group of institutions involved in R and D was created in 2000 and aimed at capitalizing all knowledge on R and D related to DMC. A strategy document was written in 2004 and updated in 2007 for the diffusion of direct seeding on permanent soil cover at national scale. Main focus of the document were: training of all stakeholders, progressive diffusion based on community level (terroir) and taking into account all aspect of the living conditions of the communities after a short survey e.g. main commodities, importance of livestock and main sources of forages, use of inputs (farm manure, fertilizers, pesticides, ..), main constraints, sources of incomes, market, etc.. This strategy document has been approved by all members of the GSDM and its main partners. Starting with a few farmers around the TAFA reference sites in 2001/2002, (5 ha, 29 farmers), the area under DMC is 3.800 ha with 7.700 farmers all over the Country in 2007/2008. The main DMC adopted by farmers in the hills (tanety) under rainfed conditions are: i) food crops (maize, rice) associated with legumes (Dolichoslablab, Vigna unguiculata, Vigna umbellata) in Alaotra lake, ii) food crops (rice, maize) on residues of Stylosanthesguianensisin the Middle West and eastern coast, iii) cassava associated with Brachiaria sp or Stylosanthes guianensis in the eastern coast and to a lesser extent, and iv) maize associated with Vigna unguiculata followed by cotton in the dry areas.

In the low lands (paddy fields) rotation of rice with vetch (Vicia villosa) or with Dolichos lablab are very common especially in the Alaotra Lake. In the coastal area, rice is followed by Vigna unguiculata. The main effects of DMC are mainly observed after 3 years of good biomass accumulation. The effect is seen as an increase in yield, a drastic decrease of Striga asiatica (Middle West) and an increase in soil microorganisms and macro-fauna (lombrics, worms...). Pests like cutworms (Heteronycusplebejus) on crops like rice cultivated with DMC techniques increase in some areas (Alaotra Lake), but are reduced in other areas (highlands) . A key issue in extension of these knowledge (and know-how) intensive techniques is capacity building. Training on DMC techniques and farm analysis/diagnosis is a necessary, but not sufficient, condition to extension. It usually takes 3 years to build efficient extension teams able to perform a real advice at farm level, to propose efficient solutions to actual farmers' constraints, means and objectives. Extension is largely eased when DMC systems can be proposed to overcome a major constraint to agriculture (like Striga infestation in the Middle West), unreliable paddy field irrigation (Alaotra Lake), possibility to reclaim uncultivated land, or systems with very limited inputs (all zones). Inversely, some conditions may slow down their extension: unreliable land tenure, poor access to credit and agricultural inputs, poor marketing channels, very small scale agriculture, etc. Farmers need to be helped to improve local socio-economic situation (promoting farmers' organizations, easing access to credit, etc.). Integration agriculture/livestock may be seen as constraints (in case of very high cattle pressure on natural resources) or an advantage for extension of DMC systems (increase of forages production through DMC). In all cases, the first 2-3 years of transition from conventional systems to DMC are crucial and require proper accompaniment of farmers by extension staff to help them to face new situations. After 3 years, extensionists support to farmers can be reduced.

Madagascar is known as one of the biggest rice consumer per capita in the world. In the past, most of the rice was produced in the lowlands or in terraces under irrigation. Nowadays, due to a rapid population growth, the hills known as tanety, which generally have low fertility, high acidity and are very susceptible to erosion, are used for rice

production. Screening of new rice varieties by the FOFIFA1 has allowed rice production in many part of the Country under rain fed conditions (Alaotra Lake, vast areas of the Mid West, part of the Highlands...). However, fertilizer use is very limited (less than 10 kg ha-1 year-1 on average) and its cost is increasing, when yields of most food crops on the tanety are generally low without high input of fertilizer, lime and organic manure.

Besides rice, corn, cassava, sweet potatoes, potatoes and beans are the main food crops. Madagascar is also a country of extensive cattle rearing with an important problem of feeding during the 6 months long dry season. Vegetation cover is also low due to recurrent bush firing. Forest cover, for instance, is only around 20%.

Thus, the main constraints to agriculture are poor and acidic soils, very small scale agriculture with very limited means, high transportation cost (raising costs of inputs and reducing selling price of products), lack of farmers' organizations and agricultural services). Furthermore, in some areas like the Mid West and the South West, cereals production is limited by Striga asiatica. For all these reasons, DMC has been experimented and extended to restore soil fertility and to enable farmers to grow crops on the degraded lands, to achieve reasonable yields with minimum inputs.

Based on the ideas of L. Seguy from his experiences in Brazil, the first experiments on DMC were initiated by the NGO TAFA and CIRAD, in the highlands in 1991/92, and progressively extended in various contrasted conditions. In 2000 a workshop was organised in Antsirabe to discuss the main constraints during this first period of research and extension. The GSDM2, a group of institutions involved in the diffusion and research on DMC was created with the objectives of capitalizing research and extension results on DMC and finding means to scale up the extension in the main areas of the Country.

Both TAFA and GSDM have been funded by the French Agency for Development AFD3 and the Malagasy Government.

1. Adaptation of DMC for the main agro ecological zones of Madagascar

Different DMC systems were tested in the main agroecological zones of Madagascar comparing zero tillage with conventional tillage on long term experiments conducted by the NGO TAFA (TAFA, 1991 to 2000). These agro ecological zones include:

• The high altitude zones (1000 m to 1500 m asl) with semi-temperate climate (type Antsirabe city) on ferralsoils with 6 months long rainy season (1300 mm year-1) and 6 months long dry season with low temperature (frost may occur in July). The first experimental site (1500 m asl) in this zone started in 1991 and three other sites were initiated in 1994 to cover the range of soil fertility, from very unfertile soils to rich volcanic soils. The site of Antsampanimahazo is now in its fifteenth year of continuous DMC practices.

• The dry climate of the South West (rainfall: 300 to 600 mm year-1) with two experiments sites on ferralsoil and on fersiallitic soil which have been cultivated for 15 years with DMC techniques.

• The warm and humid climate of the eastern coast (1500 to 2500 mm year-1 of rain) with two experimental sites initiated in 1998.

• The medium altitude climate (Alaotra Lake, 800 to 900 m asl) with 600 to 1200 mm year-1 of rain where 3 experimental sites were initiated in 1998 on ferralsoils, on alluvial soil and on alluvial soil in paddy field with very unreliable irrigation (RIA4). All these sites are entering their eleventh year with continuous DMC.

In 2005, reference sites and demonstrations plots were also initiated by the GSDM in close cooperation with the French NGO GRET in the driest part of the Country in the South (Ambovombe) where wind erosion and insects damage also are very important.

Thus, a large set of DMC systems was created in each zone, trying to fit as well as possible in the local environment and to propose a range of options for farmers with different means, constraints and ambitions.

1FOFIFA : National Institute of Agricultural Research and Development

2GSDM : Groupement Semis Direct de Madagascar

3AFD : Agence Française de Développement

4 RIA : Rizières à Irrigation Aléatoire (Unreliable irrigation paddy Fields)

Results of all these experiments showed significant differences between conventional tillage and DMC systems in terms of yield and soil improvement. For instance, significant amount of C storage was measured in the 0 to 20 cm horizon in the South West (13 years DMC), in the humid climate of the East cost (8 years DMC), and in the Alaotra Lake (8 years DMC) (Razafimbelo et al, 2007). However, high variations exist between the many kinds of systems and the different agro ecological zones. Although some very efficient systems show a fast improvement, it usually takes 2 to 3 years to observe marked differences in yield.

The first experiences of extension of these systems (before 2000), with very limited means, showed that:

• DMC systems needed to be locally adapted, to the bio-physical conditions and to the socio-economic environment,

• Training, capacity building and sensitization of top level managers, technicians and farmers were key issues

• There was a need for better information and communication,

• Monitoring extension was important

In 2000, the GSDM was created to address these issues, gathering the main organisms involved in research, training and extension of DMC in Madagascar, aiming at:

• the coordination and programming of research, training and extension activities on DMC

• the capitalization of all scientific knowledge related to DMC;

• the definition of strategies for training of all stakeholders and extension of DMC;

• and the monitoring of all activities in the DMC extension.

From 2004, with the funding of important projects on DMC by AFD (French Agency for Development) and the Ministry of Agriculture, Livestock and Fisheries, and latter other projects (funded by EU, KfW, world bank, etc.) large scale extension of DMC systems could really start, most of these projects being under the umbrella of a large national programme called BV-PI (Bassin Versants-Périmètres irrigués)

2. Extension of DMC in Madagascar

The evolution of areas under DMC in Madagascar is given on figure 1 for the 3 cropping seasons C1, C2 and C3.

C1 is the main cropping season, possible all over the country, during the rainy season. C2, an intermediate season is possible only where the rainy season is long enough (South East, Highlands), or in the low lands under a climate with a long dry season. C3, during the dry season, is possible only where water is available at that time. Logically C2 and C3 represent small areas as compared to C1.

It appears from figure 1 that the area under DMC has steadily increased over the past years, especially for the main rainy season (C1). The fastest extension is observed for upland fields (tanety), where erosion and soil degradation is a major threat.

4V№ JM0

I JODD = iuhi .

m Mam rkrvy season |EC|

Hlntr-n relaiei,M( f iWI IQJ

■ Cft^Wr WiiCrt tflVflH

Figure 1. Evolution of areas under DMC in Madagascar

The main DMC systems, adopted preferably by farmers vary with the agro-ecological zone, the socio economic conditions and the plot characteristics. However, some main features can be identified.

• On soils with low fertility, generally on eroded slopes, farmers adopt preferably low input (low risk) commodities: groundnut or peanut, cassava, grown on crop residues (when available) and associated with Stylosanthes guianensis or Brachiaria sp. to produce a high biomass for the next season. After one to three years (according to the soil and climate conditions, but also the use of the cover plant as forage) of soil regeneration by the cover crop, plants like rice or maize can be cultivated. Thus, the association Cassava + Brachiaria is very common (CHARPENTIER H., 2005) on compacted soils, and all associations with Stylosanthes are very much appreciated as they allow cultivation of the next crop with very limited inputs and risks.

Trees and forage plantations are other options, especially in milk producing areas.

• On soils with relatively good fertility (soil developed on volcanic parent material, alluvial soils accumulated in the bottom of the hillsides, known as baiboho, etc.) the main systems are based on crop rotations and associations: rice can be cultivated on residues of a previous crop associating maize and Vigna unguiculata, Mucuna utilis, Dolichos lablab, Stylosanthes guianensis or Brachiaria ruziziensis. When the plant associated to maize is perennial, it can be kept for biomass production the following year. The best mulch (>15 t ha-1 DM) is obtained with Stylosanthes guianensis: this can be achieved in one season at low altitude but at higher altitude (>800 m asl), Stylosanthes guianensis needs two seasons to get such amount of residues.

• In the Mid West where soil fertility is initially rather high (soils from basalt) but Striga asiatica is a major problem, rice is grown on a thick mulch of Stylosanthes (installed in a crop and grown for two years) which totally suppress Striga asiatica.

• On a good stand of Cynodon dactylon it is possible to apply glyphosate and to sow directly a legume crop (beans, peanut, groundnut..). This cost effective DMC system works very well (RAKOTONDRAMANANA et al, 2005) but the main constraint is that Cynodon dactylon may be used as grazing area during the dry season.

As soon as the climate (or the water availability in low positions) allows it, short cycle cover crops are planted in C2 to increase the total amount of biomass used to provide a better soil cover during the dry season: these are oats (in pure stand or associated with another crop), beans, radish, rye grass. Very valuable crops like potatoes also can be grown.

In the coastal areas where there is only one month of dry season, cover crops like Stylosanthes or Brachiaria can be planted in C2 season.

The cover crops during the dry season (C3) are mainly Vicia villosa (vetch) or Dolichos lablab or oats. These two cover crops give good residues for the following rice. Vetch is extending very fast in the Alaotra Lake in the last 3 years.

3. Significant results of DMC diffusion in Madagascar

In the process of crop rotations in DMC, the soil is accumulating organic matter over time and normally the yield and the profit of farmers are increasing. In the Alaotra Lake, over a five years period of DMC extension by BRL5, the yield of rice and corn is regularly increasing with the number of years under DMC (fig. 2) (BRL/ BVLAC, 2008). Similar tendency is obtained by FAFIALA in the Mid West over a 3 years period only (FAFIALA, 2008).

Farmers' profit also regularly increases, not only due to yield increase (of the main crop and the cover crop) but also thanks to decreasing labour costs (no tillage, less weeding).

The valorization of labour (man.day per ha) for the main systems adopted by farmer in the Alaotra lake is given for 2007 and 2008 on fig.3 (R. DOMAS et al, 2008). It shows a clear increase of the profit obtained from a day of labour with these systems. The longer the cultivation under DMC, the larger the profit per day, with a clear effect from the first year. Similar results were obtained in the mid West by FAFIALA (FAFIALA, 2008).

4. Lessons learned from DMC extension in Madagascar

The rate of DMC adoption by farmers largely varies between the different regions (figure 4):

5BRL : diffusion organism operating on DMC in Madagascar

Figure 2. Evolution of yields of Maize and Rice as a function of years of DMC in the Alaotra Lake (adapted from BRL data)

re ■u

I I I II

Years of DMC

Figure 3. Value of Man day (Ar ha-1), BRL 2007 & 2008

Some lessons can be learned from these experiences:

The techniques/systems must be locally adapted to fit the bio-physical conditions and the socio-economic environment. As a consequence of this, extension will be easier (and thus faster) in some situations than in others. In the Alaotra Lake, in a rather favorable environment (medium scale farming, some production means, some capacity to invest), the proposed DMC systems are well adapted to the main constraints and propose attractive solutions for farmers (for paddy fields with poor water control, for uplands allowing reclamation of abandoned land and cultivation of upland rice, etc.). On the opposite, more difficult conditions (very small scale farming, no investment capacity, high pressure on crop residues needed for feeding animals and even used as fuel, high population density with very intensive land use, etc) as in the highlands makes it more difficult to adapt DMC systems and propose really attractive solutions, with a rapid and visible impact.

In any cases, in such conditions, the proposed systems/techniques should aim at reducing risk (especially when risks of failure are high: unreliable climate, thieve, pests,.) putting emphasis on low inputs systems to succeed with small scale farmers (MICHELLON R., 2005, Seguy, 2006, 2007, 2008). In this respect, the rapid extension of Stylosanthes guianensis in many conditions can be explained by the possibilities it offers to increase production with very limited work and inputs. Its development is only limited by high altitude (cold temperatures) which reduces its growth and make it not compatible with high population density (thus high pressure on land). Techniques such as soil smouldering also can be very interesting (rapid increase in soil fertility when investment is limited in labour) However, availability of burning materials is often limiting the use of this technique.

Some situations can be very favorable for the extension of DMC, when a major constraint (which can be overcome by DMC) limits the efficiency of traditional systems. The very rapid extension of DMC in the middle

west can be largely explained by the fact that these systems provide a very attractive solution to the very severe problems of striga, with a rapid impact on yield and profits. On the eastern shore of the Alaotra lake, the lack of paddy fields surely is a reason explaining the rapid extension of DMC, which allow upland rice cultivation with remarkable results.

Human resources are a key issue. DMC systems/techniques are knowledge intensive. They are not a simple recipe and the choice of the system but should be carefully identified from a clear diagnosis (agronomic, but also socio-economic). Without well trained extension staff, any attempt to extend such techniques cannot be successful. Technical knowledge (and know-how) is important, but also ability to conduct diagnosis, to anticipate and organize logistical aspects (as planting time is very short and a delay is very prejudicial, every operation should be planed carefully), and to establish a real dialogue and exchanges with farmers. It usually takes 2 to 3 years to build efficient teams, as shown in the Alaotra Lake. The first 2 years, the main cause of abandon by farmers was technical failure. With training and experience, the number of abandon after 3 years was largely reduced, and the causes were more socio-economic causes (land tenure, decrease in marketing price due to high production, etc.). A major difficulty is to build teams in time, as the turn-over of extension staff is often rapid as working conditions are often regarded as difficult. As a consequence, rewards and incentives have to be given to motivate the teams.

Figure 5. Evolution of areas under DMC in the main agro-ecological zones of Madagascar

• Apart from extension staff training, sensitization of policy makers, top managers and researchers also is important.

• When credit and input provision is organized by development projects, it should be done very carefully, and only on a temporary basis being just an incentive for the first years of transition from traditional to DMC systems. After 1 or 2 years, credit should be transferred to the formal credit organization, and distribution of inputs should be done through farmers organizations dealing with the private sector.

• A major difficulty in extending DMC systems is the availability of the biomass needed for covering the soil. The global biomass production can be increased by several means: plants association, succession, use of fertilizer or soil smouldering, reclamation of abandoned land, etc. However, it will always be limited in some conditions (dry climate, very degraded soils, high altitude). In case of very high pressure on the produced biomass (for animal feeding as in milk producing areas, when population density is very high, etc.), DMC systems have to prove that keeping the biomass on the ground will be more profitable than using it for another purpose. This can take a few years, and makes extension of these systems more difficult, longer and more expensive.

• Production of seeds and planting material for large scale extension should be organized from the beginning as their lack can be a serious obstacle to rapid extension. They should be produced locally as much as possible, by farmers themselves.

• Land tenure, when very unsecure, can be a major problem which should be address cautiously (facilitating the provision of land titles when possible, negotiating long term renting contracts, etc.).

Conclusions

Extension of DMC in Madagascar is going on, but large differences exist between regions. The best results are obtained when a conjunction of factors is achieved: Well adapted DMC systems, providing attractive solutions to major problems faced by farmers (shortage of paddy field, striga, etc.) with limited risk, well trained and motivated extension staff, rather secure land tenure, rather favorable conditions (climate, market opportunities, etc.). This is the case in the Middle West (striga), the eastern part of Alaotra Lake (lack of paddy fields), and the south-east (reclamation of hydromorphous soils) the best progression being observed in the areas where lowland paddy fields are limited. In the other zones, extension is slower, due to lack of human resources (extension started later than in other zones and the teams are still in a learning process), needs of research for more adapted DMC systems with a faster impact on production with available means, and/or need of more time to demonstrate the interests of these systems.

In any case integration with livestock is a big challenge because crop residues are part of the animal forages especially during the dry season.

Furthermore, extension of such techniques is a long term process. The important needs for training and technical support of farmers during the first years (at least 3 years) of transition to DMC systems is costly, especially with small scale farmers. This extension cost is expected to decrease from the 4th year onwards.

References

BRL/BVLAC. (2008). Rapport de campagne 2007-2008. AMBATONDRAZAKA: BRL AMBATONDRAZAKA.

CHARPENTIER H., R. R. (2005). Itercopping cassava with Brachiaria sp on dégraded hillsides in Madagascar. IlIrd Word congress in CA. Nairobi: GSDM.

FAFIALA. (2008). Rapport3ème trimestre 2008. ANTANANARIVO: FAFIALA.

GSDM. (2007). Stratégie du GSDM pour la mise au point, la formation et la diffusion des techniques agro-écologiques à Madagascar. ANTANANARIVO: Groupement Semis Direct de Madagascar.

MICHELLON R., R. I. (2005). Conception de systèmes de cultures sur couvrture végétale permanente avec minimum d'intrants sur les hautes terres malgaches. IIIrd World congress on CA. Nairobi: GSDM.

R. DOMAS, H. A. (2008). Rapport de synthèse BRL à la Cellule BV LAC. AMBATONDRAZAKA: BRL Madagascar.

RAKOTONDRAMANANA, H. O. (2005). The use of Cynodon dactylon as soil cover for direct seeding in Madagascar. IIIrd World Congress in Conservation Agriculture, Nairobi, Kenya. Nairobi: GSDM.

Séguy, L. (2006, 2007, 2008). Rapport de mission à Madagascar. Montpellier: CIRAD.

T. RAZAFIMBELO, A. L. (2007). Stockage de carbone dans les sols sous systèmes en semis direct sous couverture végétal suivant différents contextes pédoclimatiques; Cas du Sud Est, du Centre Nord et du Sud Ouest de Madagascar. Terre Malgache N°26, AVRIL 2008, spécial Semis Direct, Université d'Antananarivo, Ecole Supérieure des Sciences Agronomiques (pp. 21 - 24). ANTANANARIVO: Centre d'Information et de Documentation de l'ESSA.

TAFA. (1991 to 2000). Rapports annuels. ANTSIRABE: TAFA.

Direct Drilling is Behind Agronomy of Opportunity in Tunisia

Moncef Ben-Hammouda*1, Khelifa M'Hedhbi2 , Hatem Cheikh M'hame D1 and Houcine Ghouili1

1 Laboratory of Crop Physiology/Department of Agronomy and Rural Economy, Ecole Supérieure d'Agriculture du Kef ; Le Kef 7100, Le Kef - Tunisia 2Centre Technique des Céréales, Tunisia (*Corresponding author: Benhammouda.moncef@iresa.agrinet.tn)

Tunisian climate is mediterranean, characterized by irregular, sudden, intense and relatively low rain-fall. Land degradation is continuing, water resources are becoming scare, and energy cost of farm products is continuously getting high. Consequently, cereal producers can hardly make an economic return, while practicing conventional agriculture based on conventional drilling (CD). Conservation agriculture based on direct drilling (CA/DD) gives farmers a chance to protect soils and rebuilt their fertility for an efficient use of any available form of water (rain-fall, irrigation). Such desirable efficiency does not come only by the use of the appropriate crop species, but necessarily by reducing water evaporation. To do so, a permanent mulching on the soil surface is the pivot of CA/DD. Since rain-fall fluctuates from one year to another, crop sequences should parallel with such conditions. Some couloirs have early rains (September-October) and late rains (May-June) too. In Bou-Salem (Governorate of Gendouba), early and late rains accounted for 26.2 % and 19.9 % of the 07/08 total rain for cereal growing season (September/07-June/08), respectively. These rains are not well capitalized in cereal production, when applying conventional agriculture. So, coupling the site specific approach and agronomy of opportunity is imperative to lift up farm productivity.

The climate (rain, heat) of production sites should be characterized to better define growing seasons and make the appropriate agronomic sequence. Then, the agronomy of opportunity (producing the maximum of biomass whenever the climate and the biology of the desired crop are favorable) could be applied in different scenarios, under rain-fed and/or irrigation conditions. There is no static scheme to crop the land, and it is rather a dynamic management of soil, crops, and water. A particular emphasis should be put on use of strictly seasonal (fall, winter, spring, summer) cereals and legumes in order to make a continuing cropping with two-three crops a year. A potential scenario could be a fall-barley/spring-peas/summer short season-sorghum hybrid.

Actually, few crops [barley (Hordeum vulgare), oat (Avena sativa), sorghum (Sorghum bicolor), millet (Pennisetum glaucum), african Luzerne (Medicago sativa)] are used as cover crops and others still under experimentation. So, AC/DD is a new ag-technology using the same species cropped in conventional agriculture but sometimes for a very different purpose. For example, barley may be sown first to be grazed, then according to the rain-fall a farmer has the choice to keep grazing or remove his flock out of the field and either seed a spring crop or let barley plants go to grain filling stage. Therefore, barley becomes a multipurpose crop when applying agronomy of opportunity. Some agronomic scenarios were successfully conducted. Sorghum was grown after a feed cereal (oat), and a forage biomass of 11 t ha-1 and 3 t ha-1 were produced under rain-fed conditions in 2003 and 2005, respectively. Under irrigation conditions and taking advantage of luzerne winter dormancy, oat was sown and a silage biomass of 25 t ha-1 plus a hay biomass of 7.5 t ha-1 were harvested in two adjacent fields. The previous two agronomic sequences could be considered as two forms of 'relay cropping' where in former case sorghum did benefit of May-June rain and the stock of water left over by the prior winter crop (oat) in addition to leached nitrate. However, in the late case, oat [could be triticale (Triticum secale) or barley] did benefit of luzerne biologically fixed nitrogen and rain+irrigation water too.

Key words: Mediterranean climate, Conservation agriculture, Direct drilling, Site specific approach, Agronomy of opportunity

Cereals are strategic crops for Tunisia, a country located in the southern bank of the mediterranean where rain-fall is relatively low, irregular, sudden and intense. Rain variability within and between seasons could be observed within the same year or across years (Sakis et al., 1994). Under rain-fed conditions, food or feed cereals are mostly produced in the semi-arid zones (Figure 1) with a rain-fall average of 400 mm and an estimated variability of 52% over 40 years (M'Hedhbi and Chouen, 2003). In Dahmani (semi-arid zone in the North-West of Tunisia), yearly rain explained 53% of grain yield variability of bread wheat (Triticum aestivum), while in Tibar (sub-humid zone in the North-East of Tunisia) explained only 43% (Ben-Hammouda and Marouani, 1997). These kinds of results originated the interest of cereal researchers to study adaptation and yield stability with a special interest to large adaptation types of varieties (Boubaker et al., 1999). As rain, heat (temperature) is a major factor controlling grain yield, and heat units concept can be used in crop production to assess heat requirements of cereals for growth and development so as to fit any species in its appropriate environment (Ben-Hammouda et al., 1997).

Rationale

Actually, there is a growing concern toward a site specific approach for crop/cereals production and transfer of

Figurel. Bio-climatic map of Tunisia.

successful scenarios from one site to another is based on a cluster analysis (Grower, 1967) of an agro-ecological characterization to identify similar sites (DePauw et al, 1997). Some sites/zones are known to have early rain in the fall (September-October) before sowing cereals and late rain (June-July) while most cereal species are harvested or mature enough to be harvested. Under CD and rain-fed conditions both types of rains do not efficiently participate in biomass production as grains or straw (Ben-Hammouda et al., 2007). Consequently, a different way to cereal producers is needed and CA/DD appeared as an appropriate technology to take advantage of any drop of water whether it comes from rain or irrigation. This is the basis for agronomy of opportunity which is defined as the production of maximum biomass when the climate and the cropped species biology are favorable to do so (Ben-Hammouda et al., 2005, Ben-Hammouda et al., 2007). An agro-climatic characterization based on monthly water deficit and seasonal rain-fall curves would help to set up at least two crops a year such as a winter cereal (C-3 crop) and a summer cereal (C-4 crop), an example of an agronomic sequence for a continuing cropping system (Ben-Hammouda et al., 2006). But it is recommended to break up a cereal/cereal sequence by a short season legume to ovoid the depressive effect of an allelopathic crop such as barley (Ben-Hammouda et al., 2001) or sorghum (Sorghum bicolor L.) (Ben-Hammouda et al., 1995).

Agronomy of opportunity concept could be applied in many scenarios such as the following ones: i) sow a summer cover crop while waiting to harvest a mature (winter, spring) cereal, ounce receiving a late rain (40-50 mm), ii) for two crops/year: make out benefit of early rain (fall season) for the main crop and late rain (early summer) for the cover crop, or make benefit out of a dormant species to sow on an active one (oat/luzerne, double-purpose-barley/luzerne, triticale/luzerne), iii) for a potential three crops/year: make appropriate combinations out of short season variety-hybrid/species [spring peas (Pisum sativum), summer cereal, fall peas] and other cereals with strictly seasonal physiology (fall barley, winter wheat, spring wheat), and iv) use of a deeply rooted species to pump up out reached nutrients by prior superficial rooted species, and especially catch the leached nitrate.

All the above scenarios (i, ii, iii, iv) are possible under rain-fed conditions, but it easier to sow on a mulch/ residues of a dormant species when irrigation water is available. Though the first scenario is possible using a handled-bucket for sowing, only the two crops/year scenarios were tested successfully in Tunisia with sorghum on oat mulch under rain-fed conditions (Ben-Hammouda et al., 2005 ; Ben-Hammouda et al., 2006) and oat on luzerne under irrigation conditions (Ben-Hammouda et al., 2007).

Agronomic scenarios in i) and iv) could be considered as cases of a 'take-over cropping' or a 'relay cropping' and the first scenario may be convenient also when the inter-crop season is too short, so a second crop would be sown on the prior one.

Objectives

When applying conventional agriculture based on CD, farmers, technicians and even agronomists deal basically with cereal production as a dependant variable of a simple regression on water whether it comes from rain or irrigation. This kind of attitude leaves little room for soil as water reservoir and physical container for both chemical and microbial activities that are closely tied with soil organic matter (OM) status. In soils with low OM rate, water of little rains either percolates quickly especially in sandy soils or gets back easily to the atmosphere giving a tiny chance to an active growing cereal crop to consume enough water. The same could be true for a cereal crop under irrigation conditions.

Applying the agronomy of opportunity concept in AC/DD is aimed to: i) rebuilt the soil by improving its fertility, ii) improve water use efficiency to produce the maximum biomass, iii) develop new agronomic scenarios with the use of a permanent crop residues/mulch (dry, green), and iv) rethink the purpose of usual cropped species in conventional agriculture.

Methods

The AC/DD was introduced in Tunisia since 1999/00 (Ben-Hammouda et al., 2005) with an innovative approach of experimentation. Yield trials were made in the farm and field lay-outs were set in a way that they handle statistical analysis over time and space (Gomez and Gomez, 1984), but in much larger plots than the ones usually used in standard experimental research stations. Out of tilling, cultural practices applied to cropped species in CA/ DD were the practices that farmers use in CD but adjusted with a nitrogen (N) compensation based on N-requirements/ immobilization (Harper, 1984) of microbial population and residues decay. Nitrogen was applied at the rate of 10 kg-N t-1-residues ha-1, when cereal residues or weed mulch is left on the soil surface. To meet the cropped species needs, potassium, phosphorus and N were supplied according to soil analysis and target yield of the cropped species. Soils of experimental fields are alkaline (pH = 8.1) with 2%-OM and a clay dominance over sand and silt. Soil moisture profile was monitored by gravimetric technique (Hansen et al., 1979). Climatic data were collected at the nearest meteorological station.

Results

1. Continuing Cropping under Rain-fed Conditions

Sorghum was sown late spring/03 (25/May/03) in a private farm at Krib (Governorate of Siliana), just after harvesting oat for silage and one week before receiving 50 mm of rain-fall (Photo 1). After emergence, sorghum plants were showered three weeks later with 20 mm, then a third time with 15 mm within two weeks interval. The climate was mild and evaporative loss of water was relatively low. Consequently, sorghum vegetative growth was active (Photo 2) enough to let roots develop deep down and sense the moisture that was out of the prior crop (oat) reach, thus giving chance to sorghum plants to take advantage of an eventual overlapping of the former and the later soil moistures. These moisture conditions favored sorghum growth till heading stage, making an estimated forage biomass of 11 t ha-1 in 2003 versus only 3 t ha-1 in 2005. This was an opportunity for cattle to feed on fresh plant material on summer hot days (Photo 3). Nitrogen was applied in fraction following standard recommendations, and

Photo 1. Sowing sorghum on 25/May/03, Photo 2. Active growth of sorghum,

after harvesting oat for silage June/03

Photo 3. Cattle grazing fresh sorghum on a summer hot Photo 4. Sorghum stands (late-August/03), after being

weather, July-August/03. grazed by cattle

grazed sorghum (Photo 4) resumed growth after an early-September/03 rain-fall of 52 mm (Photo 5). At this point, farmer can make a light grazing depending on the biomass volume or use it entirely as a cover crop for preferably a legume (forage, grain).

The above scenario did not cross any farmer or agronomist mind before 99/00, when CA/DD was introduced in Tunisia for the first time. Now, continuing biomass production under rain-fed conditions is not anymore a dream but a reality for many sites known as couloirs of early (September-October) and late (May-June) rain-falls. However, lots of farmers which are not very far from the successful experimental site still burning their residues (Photo 6 vs Photo 7).

Photo 5. Sorghum re-growth after receiving an early rain in Photo 6. A summer sorghum biomass in Al-Alya/Krib, where the fall (early- Setember/03) agronomy of opportunity concept was successfully applied

2. A Convenient Production Site to Apply the Agronomy of Opportunity Concept

The rain-fall data in Table N°1 is for Sidi-Ahmed-Essalah (Governorate of Kef) located in a semi-arid zone of the Tunisian North-West.

Over a period of seventeen years (89/90-05/06), the total rain of the fall (September, October, November), the winter (December, January, February) and the spring (March, April, May) is on average equal to 395 mm. For this particular rain-fall distribution, farmers are not able to overpass the level of 13 q ha-1 under rain-fed conditions, and it is basically due to low soil OM rate, hot climate and use of physiological intermediate varieties/species of cereals. In conventional agriculture, farmers usually make one crop a year between November and June to harvest straw and grains, a kind of crop that doesn't profit much from the winter rain-fall due to severe cold. It is almost agronomy of one full year crop, and farmers still have no understanding to the benefit of a physiologically strict seasonal cereal (fall barley, winter wheat, spring wheat ...). Integrating agronomy of opportunity concept in an applied formula with a cereal species of a physiological strict season would change the technical package of cereal production in such site.

Table 1. Characteristics of seasonal rain-fall in Sidi-Ahmed-Essalah, for 89/90-05/06 time period

Item Fall Winter Spring

Maximum 290 322 215

Minimum 41 16 35

Mean 147 129 119

CV (%) 49 67 43

3. Loss of Opportunity

The site of Bou-Salem (Governorate of Gendouba) had relatively high early (October) and late (May) rains that made 26.2% and 19.9% of the total rain-fall for the 07/08 regular cereal growing season (September-May). In conventional agriculture, this kind of rain-fall is not usually productive for a November sowing of oat and March/April harvest as a silage. However in CA/DD, this scenario would allow a farmer to sow a summer cereal crop in May or use May-August period to stock water rain then sow early-September a short season (40 days) legume such as peas and ovoid a cereal/cereal sequence. The monthly rain-fall of 07/08 growing season (Figure 2) was suitable to make a continuing cropping under rain-fed conditions as it was successfully done in Krib site (Governorate of Siliana).

Stp UÜ Mm -h: -Lr- h ill h.l.i fqr thy

Figure 2. Monthly rain-fall in the experimental site of Bou-Salem, 07/08 growing season.

Photo 7. In a twenty kilometers cross site (Hammam-Byadha/Krib) Photo 8. Growing oat for silage and hay on dormant Luzerne, from Al- Alya/Krib, farmers still burn dry residues/mulch and it could be barley or triticale instead of oat

4. Continuing Cropping under Irrigation Conditions

When milk is a major product, farmers reserve large fields for luzerne production. However, winter cold inhibited its re-growth/recovery especially after a severe cut in the mid-fall (20/October/03) and consequently it underwent dormancy. When applying conventional agriculture, farmers abandon luzerne fields till comes the spring heat. But when applying CA/DD, access to even wet luzerne field becomes possible with a special drill (direct sowing drill) and oat as a winter cereal was sown. Nitrogen requirement (50 kg ha-1 of ammonium nitrate 33%-N) for oat was estimated based on soil OM analysis and residual N from luzerne, therefore only one N application took place mid-November/03. From sowing (20/Octobre/02) to harvesting (15/March/03 , 29/May/03), two adjacent fields of oat/ luzerne received 319 mm of rain-fall which was complemented with four irrigations totalizing 125 mm. In one field, a biomass of 25 t ha-1 was harvested early (15/March/03) enough to make silage and leave the space for Luzern to resume early spring growth (Photo 8), and the second field was left till 29/May/03 to produce 7.5 t ha-1 of hay, thus delaying luzerne re-growth. This silage and hay productions would not be possible without CA/DD.

Conclusion

In semi-arid zones of Tunisia, cereal producers continue to crop their land applying an horizontal technical itinerary over a wide range of agro-ecologies. Yearly rain variability is relatively high and it goes up to 40% and the same holds for seasonal and monthly rains within a year. In conventional agriculture, monoculture is the ultimate consequence that originated the break-out of soil pathogens and a sharp decline of 'cleaning' organisms. Intensive use of chemicals for high requiring cereal varieties is hazardous to both human health and environment. Soils are tilled during the summer for seed bed preparation, and therefore are exposed to heavy solar radiation which is harmful to microbial activity. Deep tillage intensifies soil oxidation which enhances OM mineralization, thus CO2 is emitted to the atmosphere and water holding capacity of the soil is reduced. Aggregates of disturbed soils, especially in heavy slopes become fragile to sudden and intense rain-fall that characterizes the mediterranean climate and particularly the semi-arid zones of Tunisia.

To cope with above conditions of conventional agriculture, AC/DD offers opportunities to cereal producers to efficiently use every little drops of water, since the soil surface is permanently covered with crop residues/mulch (dry, green) and dynamic scenarios/sequences are conducted upon given climatic conditions within sites/zones. Cereal production could be viewed as biomass production (forage, straw, grains) with a more rational relationship between farmers and the climate. So, farmers would keep producing the same cereal species they use to crop in conventional agriculture but with flexible attitude when it comes to the choice about what species to crop. This is a site specific approach for crop production. Farmer objective (grains, grazing, cover crop, water storage for a subsequent crop, rebuilt of soil fertility) may change according to rain-fall regime. So, there are no static rotations as is thought in conventional agriculture.

The most important opportunity concerns scientists/researchers, regarding an urgent need to accompany the spreading of CA/DD with basic research on different themes. For example, weeds flora is inversed in comparison to conventional agriculture and the field of phyto-pharmacy has to deal with new population dynamics. It is time also to develop new agronomic terms for AC/DD and ovoid the use of no-till/zero-till which carries over the sound of tillage while being less explicit about the use of a permanent mulching. When a farmer decide to move from conventional agriculture to CA/DD, he has to de-compact (clay pan, hard pan) and drain the soil if necessary, therefore a research is needed to develop cereal varieties with pivot type of rooting systems.

Acknowledgments

Authors are grateful to the Fonds Français pour l'Environnement Mondial (FFEM) for financing the Projet d'Appui au Développement de l'Agriculture de Conservation (PADAC) via the Agence Française de Développement (AFD). Thanks are extended to scientists from the Centre International de Recherche Agronomique pour le Développement (CIRAD-France) for their partnership.

References

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Ben-Hammouda, M., Ghorbal, H., Kremer, R.J. and Oueslati, O. 2001. Allelopathic effects of Barley extracts on germination and seedlings growth of bread and durum wheats. Agronomie 21, 65-71.

Ben-Hammouda., M., Kremer, R.J. and Minor, H.C. 1995. Phytototoxicity of extracts from sorghum plant components on wheat seedlings. Crop Science, 35, 1652-1656.

Ben-Hammouda, M. and Marouani, A. 1997. Influence de la pluviométrie annuelle, saisonnière et mensuelle sur la production du blé. Medit 4, 34-36.

Ben-Hammouda, M., M'Hedhbi, K., Abidi, L.., Rajeh, A., Chourabi, H., El-Faleh, J. and Dichiara, C. 2006. Conservation agriculture based on direct sowing. Proceedings: The Future of Drylands, International Scientific Conference on Desertification and Drylands Research. Tunis-Tunisia. pp 647-657.

Ben-Hammouda, M., M'Hedhbi, K., Nasr, K. and Kammassi, M. 2005. Agriculture de conservation et semis direct: Zone du Kef. Actes des 12emes Journées Scientifiques sur les Résultats de la Recherche Agricoles. Hammamet-Tunisie. pp 145-155.

Ben-Hammouda, M., M'Hedhbi, K., Kammassi, M. and Ghouili, H. 2007. Direct drilling: an agro-environmental approach to prevent land degradation and sustain production. Proceedings: International workshop on conservation agriculture for sustainable land management to improve the livelihood of people in dry area. Damascus-Syria. pp 37-48.

Boubaker, M., BEN-Hammouda, M. and Sakouhi, L. 1999. Adaptation et stabilité du rendement de trois espèces céréalières dans les régions semi-arides et sub-humides de la Tunisie. Sécheresse10 (4) , 273-279.

DePaw, E., Ben-Hammouda, M., Mokrane, R., Zçelik, H. and Balaghi, R. 1997. Provisional agro-climatic analysis of climatic stations in North Africa and Turkey using cluster analysis. ICARDA Report of training workshop on agro-ecological characterisation of the high land of Algeria, Morocco, Tunisia and Turkey. Ankara-Turkey. 7 pp.

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Alternative Land Uses and Farm Diversification Strategies to

Strengthen CA

Ademir Calegari

Agronomic Institute of Paraná-IAPAR, Rod. Celso G. Cid, Km 375, CEP-86047-902,

2101, Londrina, Paraná, Brazil (Email: calegari@iapar.br)

Generally the lands in tropical and subtropical regions, all over the world is intensively cultivated, and in the majority of the cases occur an absence of an integrated soil and water management system. Many farming and cropping systems where no orderly crop diversification, including cash crops and cover crops in a crop rotation system are not followed, and a continuous soil disturbance, cannot provide an adequate addition of organic carbon to the system, thus the organic matter decomposition processes are accelerated, which causes a severe decrease in the productive potential of the agricultural soil of these regions.

With the strong evidences of the greenhouse effects, the climatic changes tend to provide alterations in the distributions and precipitation levels, tending in many regions to diminish the number of events (rains) and to increase the intensity, what certainly it will lead to incur into bigger risks of erosion and, consequences losses of soil particles, water and nutrients. In this way, it is basic that the soil surface must be kept with crop residues, minimum soil disturbance (no-tillage or direct drilling the crops) and, that the soil profile presents favorable conditions to water infiltration, including a harmonic integration of soil and water conservation methods: cover crops/green manure, crop rotation, terraces, strip crops, watershed ways, etc.

In Brazil, mainly in South region for many years, water erosion was considered the great environmental problem of the agricultural sector, and the execution of programs having mechanical conservation practices, the main feature of these actions, were insufficient to control the phenomenon. Sorrenson and Montoya, 1984 have reported that in Paraná State (South Brazil) average soil losses of 10 to 40 t ha-1 of fertile soil when a traditional soil tillage system has been used. These greatly contributed to increase awareness of the problem and to lead growers to organize the search for common alternatives and solutions.

Adding organic carbon to the soil through plant cultivation, as well as keeping plant residue, preferably on the soil surface, are important measures to preserve and foster organic matter balance in the soil. Thus, plants used as cover crop, given their high capacity to produce vegetal biomass (shoot and roots) and important direct and indirect effects in the soil-water-plant system, play a fundamental role when they are an adequate part of orderly rotation systems with profitable crops.

Results obtained with winter cover crops in South Brazil including Paraná, show that significant yield increases can be attained if the proper cover crop is included in rotation system ( Muzilli et al. 1983; Santos et al. 1990; Derpsch et al. 1991; Calegari et al. 2008). Almeida and Rodrigues (1985); have shown that cover crops like black oats, oil seed radish, hairy vetch, can be effective in reducing weed population in the no-till system and consequently reducing the amount of herbicide needed. According to them there is a linear correlation between the amount of biomass produced by cover crops and effectiveness in suppressing weeds. These effects on weeds may not only be through competition for light but also the allelopathic effects achieved by plant exudates (Altieri 1995; Teasdale et al. 2007).

The positive results obtained throughout the years in Paraná and other parts of Brazil prove that cover crops and cropping rotation in a no-tillage system, are very economically feasible as well as ecologically sustainable; proving not only greater crop productivity, but also conservation, maintenance and/or recovery of soil fertility, greater biologic balance in the soil, decreasing the effects of pests and or disease; in other words they represent a very promising way to manage soils tending to sustainability. The systematization of the areas through work in hydrological micro basins and also in no-tillage today occupies almost 6 million hectares in Paraná and estimates show that the no-tillage covers more than 25 million hectares in Brazil.

Historic of the Soil Management in South Brazil

Paraná State, South Brazil is located between 26° East to 54° 30' West, and 23° 30' North to 26° 30' South, and the process of soil occupation started more or less 60-70 years ago with an absence of adequate occupation planning and use of the territory leading to serious consequences in soil and water use and management.

Unfortunately, the tropical and subtropical forests were dramatically decreased (from 84% to 24% in 1965 and less than 10% to 1984) with agriculture covering both able as well as marginal areas. The total of almost 7 million hectares cultivated with summer species: soybean, maize, beans, cotton, rice, sugarcane, cassava, sorghum, coffee, fruits, vegetables, etc., on the other hand approximately half this area remains uncultivated in the autumn/ winter, with serious risks of erosion (soil, water and nutrients losses) and also improving weed infestation and consequently increasing labor and farm production costs.

The traditional or conventional soil management system (ploughing) it was commonly used during almost 3 decades. Fortunately, the minimum soil disturbance (no-tillage), started at 1972 with a farmer experience: Mr. Herbert Bartz in Rolandia, North Paraná State, and this changed totally the history of soil management in South and also it was a positive followed late for many farmers in all country. The main objective at that time it was to control erosion in areas where soybean and wheat were intensively cultivated in southern Brazil. Afterwards, maize also began to be cultivated under this system. After this the research's system started with experiments and also trying to improve this system according different farming systems in South Brazil.

In the eighties, technical data showed that the system shouldn't be a mere new alternate soil management method, but rather evolve into a system integrated to different practices that should develop in an orderly, interrelated and dependent fashion. And so in 1984, there were around 300.000 hectares with No-tillage in Paraná (5% in the state itself), and after, in 1985, it covered an area of 800.000 hectares in southern Brazil. (Derpsch et al., 1991). Now Brazil occupies more than 25 million hectares of no-tillage system, where Paraná State is that present highest area (more than 5.7 million hectares).

The well succeed research's and framer's experience with no-tillage has promoted the dissemination in the majority of the agricultural areas all over the country. The use of cover crops like radish, vetch, lupine, black oat, rye, millet, mucunas, pigeon pea, cowpea, crotalarias, etc. and also crop rotation systems with soybean, maize, wheat, cotton, rice, sorghum, sunflower, etc., are increasing in different regions of Brazil. There are many different experimental studies and farmer results about cotton - wheat rotation which attained 2.26 to 5.0 t/ha of cotton and 1.5 to 4.0 t/ha of wheat, and also 6.0-10.0 t/ha-1 of maize and 3.2-4.5 t/ha-1 of soybean, varying during the years mainly according to the rotation system, and also affected by soil and climate conditions.

The understanding of how crop residues influence nutrient cycling and soil chemical properties combining the integration of residue management strategies into different cropping systems is a key to develop good soil fertility management. The continuous monocropping like maize - maize, rice - rice, cotton - wheat, soybean - wheat, etc., in Brazil and certainly in other regions of the world had provoked pest and disease enhancing, weed infestation, soil degradation and yield decreasing. On the other hand, the no-tillage system associated with cover crops and other soil conservation practices (conservation agriculture -CA) minimizes soil degradation process, promote changes in the soil attributes: chemical, physical and biological and also diminish the chemical external input needed.

The efficiency of the CA is reported by Calegari et al. (2008) in a long term experiment, where after 19 years of different cropping sequences and tillage management, they concluded that the no-till management sequestered 6.84 Mg ha-1 more organic C compared to conventional tillage (64.6%) at the 0 to 10 cm soil depth, 29.4% more at the 0 to 20 cm soil depth, but equivalent amounts as conventional tillage at the 20 to 40 cm soil depth. Greater amounts of soil organic carbon (SOC) were within the 0 to 20 cm depth (i.e., the moldboard plow layer). Also, the results obtained showed that when winter cover crops were used with no-till, in general, greater amounts of organic C were sequestered (Figure 01).

Continuous no-till management combined with the use of winter cover crops resulted in the greatest amount of soil organic matter in the surface soil and was the only cropped treatment that approached the undisturbed forest condition. Thus, the no-till system with winter cover crops stored greater amounts of soil organic C, strengthen the CA and serves as a management model for sustaining the productivity of Oxisols in tropical and subtropical regions of the world, one to be emulated by Brazilian farmers and others who are managing similar soil types.

Soil Organic Carbon, g kg

10 15 20 25 30 35 40 80 90

50 - o

Figure 1. Soil organic carbon for different soil management and cropping systems in a Rhodic Hapludox in southwestern region of Paraná State, Brazil. CT - conventional tillage; NT - no-tillage

The experiences in some temperate climate, shows also that the soil degradation process as a result of soil mismanagement, which has showed favorable results when the implementation of no-tillage system is achieved. Thus, the use of cover crops, crop rotation and no soil disturbance has promoted soil recovering and soil productive capacity enhancing in USA, Australia, Russia, etc.

The results obtained throughout the years in Paraná, South region and other parts of Brazil prove that cover crops, as part of the productive systems, are very economically feasible as well as ecologically sustainable; proving higher water storage into the soil profile avoiding the water evaporation process, and not only greater crop productivity of cotton, soybean, maize, rice, sunflower, sorghum, wheat, rotations, but also conservation, maintenance and/or recovery of soil fertility. In addition to this, they promote economy with nitrogenous fertilizers (leguminous plants), higher weeds control by the mulch effects, greater biologic balance in the soil, higher biodiversity decreasing pests and disease occurrence, represent a very promising way to manage soils tending to sustainability.

Possibilities to Develop a Good Soil Management

In general the lack of infrastructure is a less significant constraining factor in many Global regions, however, as the agricultural input (implements, mineral fertilizers, herbicides), and information requirements are lower than for no-tillage techniques. The switch from conventional (soil ploughing) to minimum tillage is a considerably smaller step than the direct transition to no-tillage. One of the major constraint for small-scale farmer is the increased demand on the farm management, showing the crucial issue of no-and minimum tillage, both weed control and crop residue management (Steiner, 1998). One of the greatest potential for minimum tillage, like many different soil conditions all over the world, is in sub-Saharan African, in dry savannas (800-300 mm), and within those regions in areas where ploughing the soil is widespread.

Generally the principles and concepts of the CA system comprise a holistic approach, which can be adapted for different farming systems according to agro-ecological zones, and the harmonically integration of different components, such as cover crop specie, crop rotation, no-tillage, terracing, intercropping, etc. The main aims of CA is to empower farmers to make more sustainable use of their land in ways that improve their incomes and welfare, and lead to acquire the knowledge and skills to operate systems that save labour, promote soil water retention, enhance soil fertility and improve crop yields (Calegari et al., 2005, 2008).

According to Pieri et al. 2002, the Brazilian and Paraguayan farmers experience, as well in other countries, majority of the America's, shown evidence that the CA has a potential to promote a sustainable and profitable environmental approach to make frent to the challenge of food security and alleviate rural poverty mainly at tropical

environment with vulnerable natural resources. Nevertheless the CA is an extremely complex system, and field experiences and strategies in order to validate farming systems in different agroecological zones, looking for adaptation and ways to facilitate the technologies dissemination process on farm conditions, must be improved in local conditions.

The Use of Cover Crops and Crop Rotation Developed in Paraná State and other Brazilian States

In South Brazil is very common practice the use of different multipurpose cover crops/human food and forage options and this can be promoted, mainly for small scale farmers also in semi-arid areas; they simultaneously protect and recover soil properties and feed humans and animals. Therefore, different species may be used: Vigna unguiculata (cowpea), Dolichos lablab (lablab), Cajanus cajan (pigeon pea), Mucuna pruriens (mucuna), and also some other species that improve soil properties: Pennisetum americanum (millet), Brachiaria ruziziensis, Stylosanthes sp. (Stylo), Clitoria ternatea (buterfly pea), Calopogonium mucunoides (calopo), etc.

Different agroecological zones of Paraná state and also other Brazilian regions, with several farming systems, present a large number of species of cover crops alternatives which had been largely used by farmers. These species grow in many regions in different cropping systems with cash crops such as, maize, wheat, beans, soybean, cotton, cassava, potato, groundnuts, sunflower, vegetables and also intercropped with perennial crops, such as, coffee, citrus, fruits tree, grapes, etc. Besides promote soil properties improvement, and also good response for the next crops, have been used in a multipurpose as like an animal fodder and also some species with potential to be used in a human food.

Plants used as cover crop given their high capacity to produce vegetal biomass and roots, in the soil-water-plant system, play a fundamental role when they are an adequate part of orderly rotation systems with cash and food crops and they are strengthen the CA system

5. Conclusions

The old World experience has shown that the abundance of natural resources leads individuals to immediate actions. In contrast, scarce resources stimulate economical rationality and concern over predictability; in other words, responsible actions for environmental preservation both present and future.

The No-tillage System leads to better work distribution throughout the year, which results in the elimination of soil tilling, harrows and mechanical control over weeds. This condition will provide more time to arrange plant and manage different activities for better land diversification. With this system there is a significant reduction in soil loss, fertility improves, better efficiency in getting soil water, crop yields increase, and there is greater production stability, in addition to the possibility of permanently using the land, thus proving that it also contributes to agricultural system sustainability.

References

ALMEIDA, F. S.; RODRIGUES, B.N. 1985. Guia de herbicidas. Contribuido para o uso adequado em plantio direto e convencional. IAPAR, Londrina, PR. 482 p.

ALTIERI, M.A. 1995. Agroecology. The science of sustainable agriculture. Westview Press, Colorado, USA. 2nd ed. 433 p.

BOLLIGER, A.; MAGID, J.; AMADO, T.J.C.; SKÓRA NETO, F.; SANTOS RIBEIRO, M. F.; CALEGARI, A.; RALISCH, R.; NEERGAARD, A. (2006). Taking Stock of the Brazilian "Zero Till Revolution": A Review of Landmark Research and Farmers' Practice. REVIEW ARTICLE. ADVANCES IN AGRONOMY. Vol. 91, Pages 47-110.

CALEGARI, A. (1995). The effects of tillage and cover crops on some chemical properties of an Oxisol in South western Paraná, Brazil. Dissertation Thesis. University of Aberdeen, Department of Plant and Soil Science. Aberdeen, Scotland, UK.

CALEGARI, A.; RALISCH, R.; AND GUIMARÁES, M. F. (2005). The effects of winter cover crops and no-tillage on soil chemical properties and maize yield in Brazil. In " III World Congress on Conservation Agriculture". Linking production, Livelihoods and Conservation. 37 October, Nairobi, CD-ROOM.

CALEGARI A.; HARGROVE, W L.; RHEINHEIMER, D. S.; RALISCH, R.; TESSIER, D.; TOURDONNET, S.; GUIMARÁES, M. F. (2008). Impact of Long-Term No-Tillage and Cropping System Management on Soil Organic Carbon in an Oxisol: A Model for Sustainability. Agron. Journal 100:1013-1019 (2008).

DERPSCH, R.; ROTH, C. H.; SIDIRAS, N.; KoPKE, U. Controle da erosao no Paraná, Brasil: sistemas de cobertura de solo, plantio direto e preparo conservacionista do solo. GTZ, Eschborn, Alemanha e IAPAR, Londrina, Brasil. 1991, 272 p.

MUZILLI, O.; OLIVEIRA, E.L.; GERAGE, A.C.; TORNERO, M.T. Adubaijao nitrogenada em milho no Paraná. 2. Influéncia da recuperado do solo com a adubagao verde de inverno nas respostas a adubagao nitrogenada. Pesquisa Agropecuária Brasileira, Brasilia, DF, 18:23-27, 1983.

PIERI, C.; EVERS, G.; LANDERS, J.; O'CONNELL, P. & TERRY, E. (2002). No-till farming for sustainable rural development. Agriculture & Rural development working paper. The International Bank for Reconstruction and Development Rural Develop'ment Department. Washington, DC, USA. 65p.

SANTOS, H.P.; REIS, E.M. & PEREIRA, L.R. (1990). Rotajao de culturas. Efeitos no rendimento de graos e nas doenjas do sistema radicular do trigo de 1980 a 1987. Pesq. Agropec. Bras. Brasilia, 25(11):1627-35.

SORRENSON, W.J. & MONTOYA, L.J. Economic implications of soil erosion and soil conservation practices in Paraná, Brazil. Report on a consultancy, IAPAR, Londrina, GTZ, Eschborn. 1984.

STEINER, K. G. (1998). Conserving natural resources and enhance food-security by adopting no-tillage - An assessment of the potential for soil-conserving production systems in various agro-ecological zones of Africa, TOEB/GTZ , Eschborn.

TEASDALE J. R.; BRANDSAETER, L. O.; CALEGARI, A.; SKORA NETO, F. (2007). Cover crops and weed management. In "Non-chemical weed management: principles, concepts and technology". Edited by Mahesh K. Upadhyaya & Robert E. Blackshaw. Reading, UK. p. 49-64.

A Model Suiting Small Farm Diversification : A Case Study from India

Gurbachan Singh

Director, Central Soil Salinity Research Institute, Karnal, 132 001, Haryana, India (Email: director@cssri.ernet.in; gbsingh@cssri.ernet.in)

Nearly 65 percent of the Indian population is dependent upon agriculture to earn livelihood and employment. More than 50 percent of the farmers in India cultivate less than one ha (2.5 acre) land holding. To earn reasonable livelihood from such a small land holding for a family of 5-6 persons and an equal number of cattle is a debatable issue. Further, in the present scenario of increasing human and livestock populations; decreasing land to man ratio; conversion of productive agricultural lands for non-agricultural use; deteriorating natural resources (soil, water, climate and biodiversity) and decreasing total factor productivity (in single crop, commodity and enterprize based farming), a new research and development strategy is called upon to restore livelihoods of small and marginal farmers. Concerns of quality conscious society with increased demand for organic food, increasing indebtedness of farmers; WTO agreement and climate change trigged frequent occurrences of natural calamities like droughts and floods, heat and cold waves are other compelling reasons of a paradigm shift in our approach from single crop, commodity and enterprize based farming to multienterprize agriculture. In the past, vast synergies available with different farm enterprizes remained largely under-exploited due to crop or commodity driven policies. Changing consumption and demand patterns and emerging marketing and trade opportunities are offering ample opportunities for greater diversification of agriculture systems to suit to the declining size of land holdings in India. The potential of integration of dairy, poultry, piggery, duckery, fishery, beekeeping and horticulture with dominant crops/cropping systems needs to be exploited to make judicious use of farm inputs, resource management, regular income and year round employment generation on the small land holding. A comprehensive information about the multierterprize agriculture model tried at the Central Soil Salinity Research Institute (CSSRI), Karnal to improve water, nutrient and energy use efficiency in reclaimed/salt stressed environment is reported in this paper. Two years results indicated that a total gross income of Rs. 600-800/day can be generated from about 0.6 ha land area when fisheries, dairy, horticulture, poultry, duckery and mushroom cultivation are integrated and byproducts of these enterprizes are recycled within the system. Cultivation of vegetables on the dykes of the fish pond yielded about Rs. 300-400/week throughout the year. The model revealed that animal dung from the dairy component can be used as feed for fish, to generate biogas and electricity and to make compost to practice organic agriculture. The compost generated through decomposition of crop residues with cow dung in a series of compost pits was sufficient to meet nutritional requirement of fruit trees and vegetables planted on the dykes of the fish pond. Since no chemicals (fertilizers and pesticides) were used to grow vegetables and fruits during the study period the produce can be graded as organically produced. The preliminary experiences reveal that large scale adoption of such multienterprize agriculture will require an effective network of marketing, post harvest processing, value addition, cold chain, specialized handling and transport system, marketing intelligence, price support and export opportunities. Required research, development and policy initiatives to up-scale this kind of diversification in small farm holdings are also discussed.

Continuous cultivation of rice-wheat cropping system for over four decades in Indo-gangetic alluvial plains has set in the processes of degradation in the natural resources of water, soil, climate and biodiversity. Depletion of under ground water, declining fertility status associated with multiple nutrient deficiencies, increased concentration of green house gasses in the atmosphere owing to large scale burning of rice and wheat residues are some of the end results of this farming system. Most of shallow cavity tube wells (centrifugal pumps) in the Punjab and Haryana states have gone out of use consequently these being replaced with deep bore wells (submersible pumps) which cost now more than one lac rupees that a small farmer do not afford. Apart from these, the average size of land holdings continues to fall, making profits from these crops to decrease and thus causing unsustainability and migration of farmers to urban areas and also selling of agriculture lands. Nearly 50 percent of the farmers in India cultivate less than one ha land holding. A farmer with a family of 5-6 persons and almost equal number of cattle is unable to coup-up with his daily expenditure from rice-wheat rotation. The recent National Sample Survey figures indicated that 40% farmers in India intend to quit farming. Scientific efforts made in the past to improve soil and water quality and to moderate green house gas emissions through better management of inputs and practices have not yielded tangible results to hault this degradation trend. Rice-wheat cropping system provides income to farmers only twice a year when the crops are harvested during early summer or early winter but a farmer needs regular income to meet out his day-to-day needs. This, therefore, calls for an urgent need to reorient the present ways of doing agriculture to those that can improve water productivity, increase use efficiency of nutrients and energy as well as provide regular income to meet farmers daily needs. There is also a need to reverse the natural resource degradation trend and restore the farmers' confidence in agriculture. Increasing income of the farmer per unit land and water by shifting from a crop, commodity and enterprize based agriculture to integrated multi-enterprize system

is called for. Some research efforts made in the country have indicated the superiority of integrated farming system approaches over the single crop and commodity based farming (Ganesan et al., 1990; Jayanthi et al., 2001; Shanmuga-sundram et al., 1995 and Shelke et al., 2001). Integrated farming system with multienterprize may pave the way for realizing increased productivity and profitability in small farms. Multi enterprize agriculture may also has the potential to decrease cultivation cost by synergetic recycling of bi-products/residues of various components within the system and also a regular source of income and employment. Keeping this in view, a multi-enterprize agriculture project was initiated at the experimental form of Central Soil Salinity Research Institute, Karnal in 2006 as a model for 2.0 ha land with interdisciplinary approach. Main theme of this project was to develop farming options/capsules, which the small farmers can adopt to earn livelihood from his one or two ha reclaimed alkali land holding and also the adopted practices contribute to the reversion in degradation of natural resources. The philosophy behind multi-enterprize agriculture is that a farmer can adopt enterprizes such as dairying, horticulture, floriculture, bee keeping, vegetable, poultry, duckery, piggery, mushroom, fisheries, gobar gas plant and solar heater etc. depending upon his resources, marketing and processing options to improve his family income and generate at farm employment for the family.

Materials and Methods

A farming system model has been developed for 2 ha land holding with following enterprizes;

i) Agricultural crop production on 0.8 ha(0.2 ha rice-wheat, 0.2 ha maize-wheat-moong, 0.2 ha winter maize-

soybean and 0.2ha pigeonpea-mustard-fodder maize).

ii) Fisheries, dairy, fruits, vegetables (on dykes of the pond), poultry, duckery, mushroom, gobar gas plant and

solar heater in an area of about 0.6ha

iii) Horticulture, vegetable, horticulture plus vegetables and floriculture on 0.2 ha each. The project has been

initiated with the following objectives in view:

• Comparative evaluation of crop, commodity and enterprize diversification options in the reclaimed sodic land under small farm holding

• To increase water, nutrient and energy use efficiency through diversified agriculture systems thereby contributing to moderate predicted climate changes

• To increase farmer income by reducing cost of cultivation through recycling and better use of residues within the system

• Quantification of chemical, physical and biological changes in soil under different land use options for improved soil health scenario

• To identify profitable, sustainable and eco-friendly agriculture model for 2 ha reclaimed land holding

Before the start of the experiment, benchmark information on initial chemical, physical and biological properties of the soil was generated from different components of the model. On an average, the initial pH2 of the cropped area was 8.1 in the upper 60 cm layer and was more than 8.5 in lower layers. The soil was low in available N, but high in P and K in all the systems. The concentrations of DTPA extractable Zn, Fe, Mn and Cu were 0.85 to 2.41; 7.51 to 18.56; 5.56 to 8.40 and 0.81 to 2.18 mg kg-1, respectively. The soil on the dykes of the pond towards west was highly alkaline with pH2 10.25 and EC 4.0 dSm-1 while in east direction the pH was 8.3 and EC 1.65 dSm-1, respectively. The surface soil layers were sandy loam in texture and in the deeper layers clay content ranged from 19-25% throughout the depth. The surface bulk density varied from 1.5 to 1.6 g cc-1. Overall, these soils behave as well drained soils with infiltration rate ranging between 5-10 cm day. Being low in organic carbon, they however, are vulnerable to dispersion and crusting especially after rain storm and are thus prone to water stagnation at times. The initial microbial biomass carbon varied from 180 to 281.1 mg C kg-1 soil. Soil respiration from 46.6 to 63.2 mg CO2 evolved g-1 dry soil and specific metabolic quotient 1.9 to 3.3. Microbial nitrogen and phosphorous flush varied from 44.5 to 72.3 and 0.6 to 2.6 mg kg-1, respectively. Dehydrogenase activity was reported in the range of 42.6 to 172.4 Mg TPFg-1 dry soil. Similarly, acid phosphates varied from 23.3 to 52.4 Mg PNPg-1 dry soil.

The tentative area under pond, dykes and other components is as under:-

Fish Pond 0.2 ha; area of dykes 118 x 8 m (western side), 72 x 30 m (eastern side) and 99 x 10 m (northern side); animal shed 15 m x 21 m; poultry shed 7.2 x 3.7 m; duckery 3 m x 6 m; mushroom 3.5 x 6 m; gobar gas plant 7m x 6m and compost Pits (3) 8 m x 4 m; 13 x 2.5 m and 8 m x 5 m.

Hundred plants of banana, 28 of guava, 30 of karaunda and 30 of amla were planted on the dykes during July-August, 2006. Inter-spaces between fruit trees on the dykes were used for raising seasonal vegetables in rotations. No chemical fertilizers and pesticides were used to grow fruits and vegetables throughout the study period. The compost prepared in the compost pits was enough to meet nutritional requirement of plants.

A multi disciplinary research team representing the disciplines of agronomy, soil science, soil water conservation engineering, plant physiology, animal sciences, fisheries and agricultural economics was involved in the in-depth analysis of respective components. The ultimate goal is to work out water, salt, energy, nutrient and gas exchange balance in the individual components and total system for modelling and upscaling.

Results and Discussion

Two years results of this multienterprize agriculture model are presented and discussed as under:

Comparative productivity and economics of the cropping systems

The productivity in different cropping systems was worked out keeping in view the quantity of marketable produce both during 2006-07 and 2007-08. The productivity in case of fodder crops represents the green fodder yield, in grain crops it is the grain yield and in case of vegetables it is the green vegetable production. The productivity obtained in different systems during 2007-08 is presented in Table 1.

Table 1. Productivity of the crops under multi-enterprise agriculture experiment during 2007-2008

Systems

Productivity Productivity Productivity System productivity

(t/ha) (t/ha) (t/ha) (t/ha)

Fodder Production

Sorghum- berseem*

Maize-oat-berseem*

Crop Production

Maize-wheat-mungbean

Soybean-maize

Pigeon pea-mustard-maize

Rice-wheat

Flower Production

Babycorn-gladiolus-marigold-sunflower

Vegetable Production

Ladies finger-tomato-tomato Ladies finger-cauliflower-bottleguard Bottle guard-tomato-garlic

100.0 7б.0

Green manured 0.7З 0.2S 7.1

0.6б Cobs+0.21 t grain+ 2.0 t stover

6.0 2.0 17.б

10б.0 7б.0

62.б* 2.S 0.1З 4.4

11,460 sticks

2.9 6.9 10.б

б.2б

2.9 + 2.S sunflower

1.З 1.2 З.З

20б.0 260.0

67.7б З.бЗ 29.41 11.б

10.2 10.1 З1.З

* = green fodder yield

Amongst the different enterprizes studied, the fodder crops gave the highest net income followed by vegetables and flowers. The financial analysis of raising different crops is given in Table 2. The results showed that wheat cultivation was more profitable compared to the rice cultivation. On the other hand, Berseem alone gave higher net income in comparison of rice and wheat put together. The benefit cost ratio in case of Berseem fodder cultivation was 5.96. The operational cost of fodder crops, in general, and Berseem in particular was much lower than the grain crops. Performance of soybean and pigeonpea was not satisfactory and proved uneconomical at the existing pattern of resource use. Several factors contribute for variation in economic analysis of each crop each year. The pooled analysis after 5 years will give clear picture of different capsules of this 2 ha model. There were more variations in the economics of fruits, vegetables and flower crops due to fluctuating market prices and availability of such produce at different times of the year. This study is also providing an additional opportunity to judge the marketing behaviour of different crops and enterprizes being tried in the model.

Dairy Component

Four buffaloes were purchased from National Dairy Research Institute (NDRI), Karnal on book value on April, 24, 2007 for a total cost of Rs.66500/-. The total milk production from buffaloes between April 24 to May 17, 2008

Table 2. Economics of crops grown during 2007-08 (Rs./ha)

Crops Operational Cost Gross income Net income B:C Ratio

Rice 28678.25 46250.00 17571.75 1.61

Wheat 17551.95 51500.00 33948.05 2.93

Winter Maize 18643.50 26560.00 7916.50 1.42

Green gram 10851.50 15800.00 4948.50 1.46

Soybean 14730.60 5355.00 -9375.60 0.36

Pigeonpea 11270.35 750.00 -10520.35 0.07

Mustard 10680.85 16925.00 6244.15 1.58

Baby corn 19815.77 21561.54 1745.77 1.09

Cabbage 18938.75 29610.00 10671.25 1.56

Cauliflower 33987.75 52000.00 18012.25 1.53

Chillies 6826.00 10000.00 3174.00 1.46

Bottle gourd 55624.75 117275.00 61650.25 2.11

Gladiolus 77902.69 109230.77 31328.08 1.40

Marigold 17308.46 38461.54 21153.08 2.22

Berseem 9232.00 55000.00 45768.00 5.96

Oat 8400.50 35000.00 26599.50 4.17

Maize fodder 11550.00 18000.00 6450.00 1.56

Maize+ Cowpea (Fodder) 10351.50 22500.00 12148.50 2.17

Sorghum+ Cowpea (Fodder) 12137.90 16000.00 3862.10 1.32

was 6263.25 litres. The total income from the sale of this milk was Rs. 1,12,834/-. Three cows were purchased from NDRI on 6th October, 2007 on book value for Rs. 41,943/-. Between October 6, 2007 to May 17, 2008, 4834.5 litres of milk was obtained which was sold for Rs. 63,610/-. Milk obtained from buffaloes and cows was sold to the staff members of CSSRI, Karnal on a concessional rate. The total milk production and revenue generated during the study period is given in Figure 1.

Figure 1. Monthly milk production, expenditure and income during 2007 and 2008

Starting from April 24, 2007 to May 17, 2008, 5.8 t of feed was given to the animals and the cost of this feed was Rs.48,000/-. Similarly, 73 t of green fodder was given to the animals. The cost of which if it is to be purchased from the market was worked out to be Rs.30,000/-. About 1.1 t of wheat bhusa costing Rs.11,000/- was also fed to the animals.

About 82 t of cow dung was obtained from the seven animals during this period. Out of which, 56.9 t was used for generating biogas from the gobar gas plant, 17.3 t for making compost, 1.7 t for making vermicompost and 5.74 t was added in the fish pond as fish feed (Table 3). The dung used in biogas plant, after production of biogas was added into the compost pits. A major part of urine of animals was added directly into the fish pond.

Gobar gas plant was established in august, 2007. The cooking gas production started from September, 2007. It was estimated that the bio-gas available from this plant can meet the cooking needs of a family of 5-6 people per day. The cooking gas was available throughout the year to meet energy and electricity needs. As an alternate/ supplement to the commercial electricity supply, three electric lamps can also be lighted using cooking gas to

Table 3. Monthly dung production (t) during 2007 and 2008 and its recycling in the system

Month Gobar gas plant Compost pits Vermi- compost Pond Total

April, 07 0.5 - - - 0.50

May 2.2 - - - 2.20

June 2.8 - - - 2.80

July 2.7 - - - 2.70

August 2.8 - - - 2.80

September 2.7 - - - 2.70

October 4.8 - - - 4.80

November 5.6 - - - 5.60

December 6.0 - - - 6.00

January, 08 2.2 1.8 - 2.20 6.20

February 2.1 1.5 - 2.30 5.90

March 3.5 1.4 0.41 0.40 5.71

April 2.5 1.9 - - 4.40

May 1.3 1.3 0.16 0.16 2.92

June 2.1 0.4 0.46 0.25 3.21

July 1.6 1.2 - 0.01 2.81

August 1.7 1.0 - - 2.70

September 3.2 2.0 0.69 - 5.89

October 4.0 2.5 - 0.12 6.62

November 2.6 2.3 - 0.30 5.20

Total 56.90 17.30 1.72 5.74 81.66

meet electricity need. Total expenditure on establishment of gobar gas plant was Rs. 12000/-. The government provides subsidy to the extent of 50 to 75% to the farmers for establishment of this facility at their farms.

Fish Production

Fish seed was added in the pond in March, 2006 costing Rs.2000/-. The fish species included catla, mirigal, rohu and grass carp/common carp. The comparative economics of fish production during 2006-07 is given in Table 4. The income is expected to increase in subsequent years.

Table 4. Economics of fish production during 2006-07 in multienterprize agriculture model

Particulars 2006-07

Fixed cost (Rs./year) 4225

Variable cost (Rs./year) 23638

Total cost (Rs./year) 27863

Fish production (kg) 1057

Gross income (Rs./year) 40391

Net income (Rs./year) 12528

B - C ratio 1.45

Bee Keeping

Beekeeping is an economic enterprize that requires less investment and space. Investment is required only in the first year when system is established. As a component of the system, 25 boxes were placed in the farming system model area. The comparative economics of this enterprize is given in Table 5.

Vegetables and Fruits Production on the Dykes of the Pond

The raised dykes of the pond were effectively utilized for raising vegetables and fruits to meet daily food and nutritional requirement of 5-6 persons and to generate daily income to meet domestic expenditure. The per month income generated throughout the study period varied from Rs. 206 to 2614. The month wise variations in income during 2006-07 and 2007-08 are given in Figure 2. The fruits planted on the dykes started bearing fruits in 2008 (about 2 years after planting). Between August, 2006 and December, 2008, 252 kg of banana, 82.5 kg of guava and

Table 5. Economics of honey production

Particulars 2006-07 2007-08 Overall

Fixed cost 6358 5250 11608

Variable cost 17807 3978 21785

Total cost 24165 9228 33393

Honey production (kg) 343 106 449

Gross income 41160 12660 53820

Net income 16995 3432 20427

B - C ratio 1.70 1.37 1.61

7.5 kg of karaunda was produced. The income from the sale of banana, guava and karaunda planted on the dykes was Rs.2529, 1237 and 105, respectively. The income from these plants is likely to be increased several fold over the years.

Figure 2. Monthly income from vegetables and fruits during 2007 and 2008

Poultry Production

The poultry component was introduced in the last week of August, 2008. The chicks numbering 120 of desi mixed breed were purchased for Rs.3000/-. In a period of first three months, about 91 chicks died because of some feed related infections confirmed by the poultry doctor. One of the hens out of the remaining birds started laying eggs in last week of December. The other hens are yet to start laying eggs. During this period, about 80 kg litter from the bedding material comprised of rice husk and excreta of poultry birds was added into the compost pit. From August to December, 2008, 264 kg feed costing about Rs.2640/- was given. The tentative sale price of the birds for meat purpose is estimated as Rs.6000/-.

Rearing of Ducks

The component of duckery was introduced from September, 2008. Hundred ducks were imported from Bhubneshwar centre of the Central Avian Research Institute, Mathura. Because of some feed relalted infections 89 ducks died between September and November, 2008. At present 11 ducks are remaining and are quite healthy but they are yet to start laying eggs. Rs.200/- were spent on the medicines for ducks. Most of the day time, the ducks swim in the fish pond and increase oxygen availability for fish. After the introduction of ducks the mortality of fish in the pond has considerably decreased.

Mushroom Production

The culture for raising mushroom as a part of the multi-enterprize agricultural system was prepared during October-November, 2008 using wheat straw and compost. Ten kg mushroom seed was imported from National Research Centre on Mushroom, Solan and was sown in different trays and was placed in environmental controlled green house made using local materials available from the residues of the crops, bamboo sticks etc. The mushroom production started from November 25, 2008. The per day production varied from 0.2 to 4.4 kg and the total revenue generated per day during the study period varied from Rs. 10 to Rs. 340.

Water Balance in the Pond

The soil water conservation engineering expert is keeping a comprehensive information on the water balance in the pond. The total water added into the fish pond was 6900m3. The water contribution through the rainfall was 1604

m3. The loss of water from the pond due to seepage and evaporation was 3329 m3 and 2554 m3, respectively during the study period. The pumping time for irrigation and input cost of water was also worked out. The discharge of tubewell was 30 Ips, depth of water table 12 m, pumping head 18 m and kilowatt required 15. Total pumping hours in one year were 64 and total units of electricity required to pump the water was 9960 units. The total expenditure was worked out Rs.4800. The monthly variations in pH2, EC and salinity of water in the fish pond were monitored during the study period. The variation in pH2 ranged from 7.6 to 8.3; EC from 0.6 to 0.8 and total dissolved salts from 380 to 520 meql-1. These values were well within the limits prescribed for fish culture in ponds (Figure 3).

Figure 3. Monthly variations in pH, EC and salinity of the water in fish pond during 2007 and 2008

Per day Returns

Weekly and per day returns were worked out for the month of December, 2008, about 2^ years after establishment of the model. The details of the sales are given in Table 6. During the month, the per day income came from the sale of milk, vegetables grown on the dykes of the pond, fish and mushroom. The revenue generated/day from milk, vegetable and fish was Rs.623/-, 114/- and 397/- respectively. The average total income generated per day during December was Rs.1134/-. In case we take 50% as expenditure per day even then Rs.570/- as net income can be generated from this model. This does not include income from mushroom. This income is likely to increase with the passage of time when other components like fruits, poultry and ducks will also start yielding revenue. In addition, daily requirement of energy for cooking and electricity generation is met without incurring any additional expenditure.

Table 6. Revenue generation details during December, 2008

Commodity

Total sale (Rs.)

Weekly sale (Rs.)

Per day sale (Rs)

Vegetables on the pond dykes Fish

Gross sale

19,316.00 3,542.00 12,297.00 35,155.00

4389.00 799.75 2776.69 7,938.00

623.00 114.00 397.00 1134.00

Acknowledgements

A multidisciplinary team of scientists is working on the project. The contribution of each of them is gratefully

acknowledged. Special thanks are due to Mrs. Sunita Malhotra and Mr. Sultan Singh for typing and final preparation

of this manuscript.

References

Ganesan, G., Chinnasamy, K.N., Bala Subramanian, A. and Manickasundram, P. 1990. Studies on rice based farming system with duck cum fish culture in deltaic region of Thanjavur district, Tamil Nadu, Farming Systems Newsletter 1 (2): 14.

Jayanthi, C. Rangasamy, A., Mythili, S., Balusamy, M., Chinnusamy, C. and Sankaran, N. 2001. Sustainable productivity and profitability of integrated farming systems in lowland farms. In: Extended Summaries (A.K. Singh, B. Gangwar, Pankaj and P.S. Pandey, Eds.), pp 79-81. National Symposium on Farming Systems Research in New Millennium, PDCSR, Modipuram.

Shanmugasundram, V.S., Balusamy, M. and Rangasamy, A. 1995. Integrated farming system research in Tamil Nadu. Journal of Farming Systems Research and Development 1 (1 and 2) : 1-9.

Shelke, V.B., Kulkarni, S.N., Waghmore, D.B. and Chauvan, A.A. 2001. Study on integrated farming system in Marathwada. In: Extended Summaries (A.K. Singh, B. Gangwar, Pankaj and P.S. Pandey, Eds.), pp 99-100. National Symposium on Farming Systems Research, PDCSR, Modipuram.

Session 1.4: Irrigated Systems

Rational and Application of CA for Irrigated Production in Southern

Europe and North Africa

Helena Gomez-Macpherson1*, Hakim Boulal12, Rachid Mrabet3, Emilio Gonzalez4

11nstituto de Agricultura Sostenible, CSIC, Apartado 4084, 14080 Córdoba, Spain

2Universidad de Córdoba, Spain 3National Institute of Agricultural Research (INRA), Tangier, Morocco 4Asociación Española Agricultura de Conservación Suelos Vivos, Córdoba, Spain

(*Email: hgomez@cica.es)

The development of sprinkler and drip irrigation has resulted in an extension of the irrigated land in the hilly areas of Southern Europe and North Africa increasing the risk of soil erosion. CA systems may reduce this risk but their adoption is quite limited. Residues and cover crop management, soil compaction and new pests have discouraged many farmers. This work presents the major problems encounter in the CA irrigated production systems in the region and introduces the most promising options.

Key words: conservation agriculture, irrigation, permanent beds system

Water scarcity is the main constraint for crop production in Mediterranean environments. Paradoxically, typical heavy rains in autumn and winter cause the main environmental problem associated to agriculture: the soil erosion. The soil lost in cultivated land has been estimated as 35 tn/ha/y in northern Morocco (Heusch, 1985) and 40 tn/ha/ y in Southern Spain (Junta de Andalucía, 2003). Although these are questionable figures, the magnitude of the problem was acknowledged in the Pan-European Soil Erosion Risk Assessment in which risk figures above 10 tn/ ha/y are relatively common in the southern European countries (Montanarella, 2005).

The development of powerful machinery last century displaced the less intensive traditional soil management methods. The new methods allowed rapid farm work and were extremely effective controlling weeds but also resulted in a reduction of soil organic matter and a deterioration of soil aggregates, and therefore, an increased risk of water and wind soil erosion. On the other hand, the irrigated agriculture land has increased in the last decades in all countries around the Mediterranean reaching nearly 4 million hectares in Italy and Spain, nearly 3 million ha in France and around 1.5 million ha in Greece and Morocco (FAO, 2008). This irrigation development was mostly associated to sprinkler and drip irrigation systems that, contrary to furrow or flood irrigation, do not require leveled land for an efficient water application allowing the irrigation of hilly fields and further increasing the risk of water soil erosion.

Conservation agriculture (CA) approaches have been proposed to reduce the risk of soil erosion (e.g. Holland, 2004). According to the European Conservation Agriculture Federation (ECAF), CA refers to several practices which permit the management of soil for agrarian uses, altering its composition, structure and natural biodiversity as little as possible and defending it from erosion and degradation. In particular, for the ECAF, CA includes direct sowing / no-tillage, reduced tillage / minimum tillage, non or surface- incorporation of crop residues and establishment of cover crops in both annual and perennial crops. The European Union promotes CA systems but leaves to each member country the decision on which approach should be followed for this promotion. In 2006, more than 15 million ha in the EU practiced a type of CA (Gonzalez, per. comm.).

In the Mediterranean basin, CA systems have been widely studied for rainfed conditions (Moreno et al., 1997; López-Bellido et al., 1996, 2000; Mrabet, 2000; Pagliai et al., 1995; Ben-Hammouda et al. 2006). The residues left on the ground help to protect the soil from the wind and the rain drops (López et al., 1998), to improve soil aggregation and fertility (Mrabet et al., 2001; Saber and Mrabet, 2002; González-Fernández and Ordoñez-Fernández, 1997) and to increase water infiltration in the soil and water availability for the crop (Moreno et al., 1997; Cantero-Martínez et al., 2007) although a minimum mulch layer is required (Lampurlanés and Cantero-Martínez, 2005). In most cases yield results unaffected although it may increase (Moreno et al., 1997; Murillo et al., 1998; Ben-Hammouda et al. 2006).

In contrast to the extensive research work in rainfed CA systems, there is a limited research work being carried out under irrigation (Boulal et al., 2008; Casa and Lo Cascio, 2008; Lithourgidis et al., 2005). This is surprising

considering that water use efficiency is a general goal in Mediterranean countries due to insufficient water irrigation allocation for covering full crop requirements, a worsening situation as irrigated land expands as well as the water demand for urban and industrial uses. The limited research on irrigated CA systems probably contributes to their limited adoption in the region. There is no information on CA surface under irrigation but we could assume that it may reach 10% of CA surface, i.e. around 400 ha in France and 125 ha in Spain, being negligible in the rest of countries. These poor figures may change in Southern Europe with new normative recently approved. For example, in Andalusia (Spain), there is a premium of 59 •/ha/y for a commitment of direct sowing during 5 years in hilly lands of 8% average slope. Furthermore, most subsidies are not linked anymore to the production of specific crops leaving farmers more freedom in the selection among available option and increasing their interest in alternatives that may reduce the production costs.

The present study aims at revising the main problems associated to CA under irrigation in Southern Europe and North Africa and at introducing the most promising systems while identifying the research needs for their development and adoption.

Cereals Based Systems

Residues management is a major limitation for no-tillage adoption in irrigated maize-based cropping systems in southern Europe. Average maize yield for the common 700 cycles in the region are higher than 12 t ha-1 (Aguilar et al., 2007). This implies that a similar amount of residues may be left in the field after harvest. Residues are necessary for improving soil quality as well as for limiting soil erosion, particularly in the hilly lands in this region (Boulal et al., 2008). However, there is a drawback to maintaining them as they affect negatively the establishment of the following crop, typically cotton, because of the reduced soil heating during seedling emergence and the increased damages by armadillo bugs and slugs (Griffith et al., 1977). In the past, residues were burnt but nowadays most farmers will incorporate them into the soil unless maize is cultivated for silage (Lithourgidis et al., 2005).

Farmers in Southern Spain also identified soil compaction caused by heavy drills used in the spring sowing, or by heavy cotton harvesters used in autumn, as another major reason for non adopting CA. Indeed, increased compaction and lower yields in CA cotton have been observed elsewhere (Raper et al., 2000) and the need of occasional deep ripping has been argued (Wild et al., 1992).

A permanent beds system has been developed in a commercial farm in Southern Europe to deal with excessive residues and soil compaction of CA irrigated maize-cotton system (Calleja et al, 2008). The crop is cultivated on the top of permanent beds with 95 cm inter-beds distance (given by cotton harvester). Two weeks before sowing, the residues from the top of the beds are shoved to the lower part of the furrow leaving a clean band of 20 cm approximately. A single row of crop is established in this band, 5 cm aside from the top centre, which is the distance at which drill's boots are deviated. The following year, the drill starts sowing at the other side of the field so the row is established 10 cm apart from preceding crop. The beds facilitate the respect of controlled traffic leaving 20 % of furrows with no traffic in any operation (sowing, treatment application, fertilization or harvest). Permanent beds systems have been used in other regions (see Govaerts et al., 2005) usually where excessive residues do not pose a problem. In Mexico, the system allows fitting two crops (wheat and maize) in one campaign (Limón Ortega et al., 2000). In Turkey, the permanent bed system facilitates the mechanic harvest and reduces the costs (Ozpinar and Isik, 2004).

Calleja et al. (2008) collected information on maize grain yield and water applied in two neighbor paddocks before and after the previously described permanent bed system was adopted (2001 and 2005 for each of the paddocks). There are a total of 7 seasons before as well as after the adoption. Additionally, some field measurements were taken after 5 years of adoption in one of the paddocks and in a neighbor traditionally tilled system. The measurements included: top residues, soil organic matter and soil water stable aggregates (determined as in Barthes and Roose, 2002) as well as saturated hydraulic conductivity, water infiltration and soil losses using a portable rainfall simulator (Alves et al., 2008; Boulal et al., 2008).

The permanent beds system had 210 g m-2 of dry residues covering the surface at sowing after 5 years of no tillage whereas the conventional system has none (Calleja et al., 2008). The mulch and the reduction in tillage resulted in an increased soil organic matter from 1.5% to 2.4% in the top 10 cm with no differences in deeper layers. This is a higher increment than the one obtained in rainfed cereal-based agriculture in the same region (Ordoñez-Fernández et al., 2007). The water stable aggregates was also significantly higher (23% for the top 20cm)

when compared to the conventional paddock. Interestingly, there were no differences in soil organic matter or aggregates between the top and bottom of furrows in spite of shoveling the residues to the bottom two weeks before sowing.

When compared with the conventional system, the permanent bed system improved the saturated hydraulic conductivity, the soil infiltration rate and reduced significantly soil losses (Sánchez-Domínguez, 2004; Boulal et al., 2008) and more so in the furrows without traffic (Boulal et al., 2007). High water infiltration is particularly important under pivot irrigation as the intensity of irrigation in the distal part can be much higher than in the central part resulting in more erosive situation similar to a heavy rainfall (Howell et al., 2002). The improved hydraulic conditions resulted in a reduction of applied irrigation without yield penalty in this commercial farm (Figure 1). A water balance model is being adapted to incorporate CA particularities for studying possible impact of CA adoption in terms of water saving and reduction of soil erosion in the region (Boulal, unpublished).

"ra* 7000 -i

E 6000 ■

5000 -

E ra 4000 -

3000 ■

t 2000

♦............

♦ Conventional Permanent beds

1996 1998 2000 2002 2004 2006 2008 Year

Figure 1. Paddock maize yield and applied irrigation before (conventional) and after the introduction of permanent bed system in Fuente Palmera (Spain)

Soil temperature is lower under a layer of residues because radiation does not reach directly the soil surface and cannot heat it. Lower temperatures slow down emergence and seedling growth of crops like maize (Griffith, 1977). This is particularly important for the maize and cotton crops sown in southern Europe because the cycle is tightly adjusted to the growing period and a late sowing is not desirable. Calleja et al. (2008) found a difference of 7.5 and 5 oC at 2 and 5 cm deep, respectively, in a permanent bed system when compared to uncovered soil in a conventional system, in agreement with Benjamin et al. (1990).

Various maize varieties have been tested in the permanent bed system established in the commercial farm during the last seven years and they appear to respond differently, some having a quicker and better establishment that reduces pest damage at seedling stage (Calleja, pers. comm.). These observations put forward the need to evaluate locally available genotypes in the permanent beds system following standard research.

Contrary to Southern Europe, the development of CA in North Africa is mostly limited by the lack of residues to cover the soil because of large feeding demand or overgrazing. Residues are needed for CA success (Govaerts et al., 2005) and the minimum required should be determined in order to develop strategies of balanced residues management. The conflict though often goes beyond farmers decisions as traditional livestock management includes feeding on cropping rests. In these cases, specific policies from authorities are necessary.

In Morocco, a central issue in irrigated agriculture is how to effectively use growing season precipitation and limited available water for irrigation. A balance between the productivity and the quality of soils must be sought as pressure on the irrigated lands is likely to increase. The balance could be realized through simultaneous use of no-tillage systems, as water conserving and soil restorative technologies, and of supplementary irrigation techniques for more efficient and economic use of limited available water. In fact, the feasibility of no-tillage for irrigated cereals has been systematically assessed since the 1990s in Chaouia region (350 mm average rainfall, Mrabet, 2008) and it continuous up to now in Sais region (450 mm average rainfall, Mrabet, unpublished). In the last, no-tillage irrigated system resulted in higher wheat grain yield compared to more conventional systems (Figure 2). In 2006, three applications of 20, 20 and 40 mm were done at selected stages of wheat while, in 2007, only two applications of 15

Figure 2. Impact of dryland and irrigated tillage system on wheat grain yields in semiarid Morocco (Mrabet et al., unpublished)

mm were possible. Ten wheat varieties were included in the study and significant interaction with tillage system was observed (data not shown). Further evaluation is needed to identify the best adapted varieties to irrigated CA systems.

Olive Orchards and Vineyards

Olive orchards and vineyards form the most extensive perennial cropping systems in the Mediterranean region. Traditionally they occupy hilly lands with the highest risk of soil erosion due to common mechanical weed control. The use of cover crops reduces this risk (Gómez et al., 2009) but, in rainfed conditions, their management in order to avoid the competition for water is tricky. In the last decades, however, the development of irrigation systems has facilitated the extension of cover crops because of more flexibility in the killing timing without increasing the risk for water competition and yield decrease.

Cover crops may be sown each year or second year or, alternatively, the natural vegetation can be left to re-grow and cover the inter rows space. Some farmers prefer to use arable crop residues or chipped bark as mulch. Any of these options accompanied by chemical weed control appear cost effective compared to tilling the soil (Jones et al. 2006). Furthermore, the use of cover crops in vineyards may also improve wine quality in soils with high water availability as in Portugal (Monteiro and Lopes, 2007) and France (Celette et al., 2008). Cover crops though can result in lower surrounding temperature and increased risk of frost damage and requires special attention to fertilization (Rupp and Fox, 1999).

In irrigated olive orchards, zero or minimum tillage improved water availability compared to conventional tillage, increasing the oil yield production by 9% (Pastor, 2005). Most irrigated olive orchards follow a system of deficit irrigation and special attention is required for a correct irrigation scheduling that avoids damaging droughts and yield penalties. In conventional orchards, Orgaz et al (2006) has proposed the use of a new crop coefficient that is the sum of i) a tree transpiration component, ii) an evaporation from the soil component and iii) an evaporation from the areas wetted by emitters. The calculations obtained with this model can be corrected during the season with current rainfall and ETo values, however, the model has not been adapted to include cover crops. The last will require an increased crop coefficient and its variation associated to herbicides use. The water balance should include higher water infiltration and reduced runoff movement than in the conventional system (Gómez et al., 2009). For citrus orchards of 50% canopies, FAO Monograph 56 (Allen et al., 1998) proposes to increase the crop coefficient from 0.60 to 0.75 if an active ground cover is present.

Research Needs

The following research themes are proposed to develop CA under irrigation on commercial basis:

• Water balance models for adjusting irrigation scheduling to CA conditions and improving water use efficiency and soil protection.

• Water balance models of permanent crop / cover crop system for minimizing competition for water and soil erosion and for improving fruit quality.

• Study the evolution of off-site movement of agrochemicals (particularly herbicides) and sediments.

• Adjust available models of evolution of residues degradation and soil physical and chemical characteristics to

CA under irrigation.

• Develop alternatives for residues management in competition with livestock.

• Evaluation of controlled traffic and periodical tillage to avoid or relieve soil compaction.

• Evaluation of genotypes for permanent bed systems and direct seeding.

A participatory research approach as in Rawson et al (2007) should be considered due to the local specificities

required for the adaptation of CA systems.

Acknowledgements

The work presented from Southern Spain and Morocco was partially funded through project AGL2005-05767.

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Implementing Conservation Agriculture Concepts for Irrigated Wheat Based Systems in Northwest Mexico: A Dynamic Process Towards

Sustainable Production

Bram Govaerts1*, Nele Verhulst12, Ken D. Sayre1, Fabian Kienle3, Dagoberto Flores1

and Agustin Limon-Ortega4

11nternational Maize and Wheat Improvement Centre (CIMMYT), Mexico, D.F., Mexico 2Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200 E, 3001 Leuven, Belgium 3Colegio de Postgraduados, Km 36.5 Carr. México -Texcoco, CP 56230, Montecillo, Mexico 4INIFAP-CEVAMEX, AP10, Km 17.5 Carr. México-Lechería, CP 56230, Chapingo, Mexico *Corresponding author (Email: b.govaerts@cgiar.org)

In this paper we use the example of the irrigated wheat based systems of North Mexico as a typical example of a step-by-step process to advance the use of Conservation Agriculture based Resource Conserving Technologies towards the final goal of the implementation of Conservation Agriculture. Sonora in northwest Mexico. This region is characterized by a desert climate, mostly sunny and dry with a total rainfall of about 381 mm per year with 253 mm during the summer cycle (May - Oct). The Yaqui Valley is one of the main agricultural production areas encompassing nearly 255,000 ha of irrigated land using primarily gravity irrigation systems fed by canals (over 80% of irrigation water) and deep tube wells (around 20% of irrigation water). Crops planted during the winter cycle are wheat (November-May), safflower (January-June), winter maize (September-February), chickpea (December - April) while during the summer cycle summer maize (May - October), sorghum (March - July), dry beans (March - May) are most common. There have been 3 main shifts in farming system practices during the last decades: (1) In 1981, the majority of the farmers were planting with 'melgas' (crops planted in solid stands on the flat with flood irrigation in basins) with only 6% of farmers in the valley planting on raised beds. However by 1996, 90% of the farmers had shifted to planting on raised beds. The great benefits from bed planting are reduced production costs, reduced irrigation water use, enhanced field access which facilitates control of weeds and other pests, and timely and efficient application of nutrients, reduced tillage, and crop residue management. (2) Another remarkable change in farmer practices has been crop residue management. In the 1992/93 cycle, residues were burned by 95% of the farmers. This practice was deeply entrenched. By 2001, however, 96% of the farmers are no longer burning but incorporating the residue. (3) Recently there is growing interest to take the next logical step in making raised bed planting more sustainable by reducing tillage and manage crop residues on the surface by reusing permanent raised beds with only superficial reshaping in the furrows between the raised beds as needed before planting of each succeeding crop, following even distribution of the previous crop residues. Therefore in 1991 the crop management team at CIMMYT started research on permanent beds to offer farmers opportunities to further reduce production cost andincrease sustainability of the system through the positive effects on chemical, physical and biological soil quality.

Keywords: permanent raised bed planting, residue management, irrigated wheat systems, resource conserving technologies

In many parts of world, agricultural practices are determinant in food production. Adoption of new agricultural technologies, intensification of agriculture and improved crop varieties have dramatically increased crop yields in developing countries (Gupta and Seth, 2007). However, modern society demands cropping systems that not only aim at stable and high yields, but also maintain soil fertility, reduce negative effects for the environment and are economically sound (Lal, 1997).

Farmers concerned about the environmental sustainability of their crop production systems combined with ever-increasing production costs have begun to adopt and adapt improved management practices for their cropping systems that lead towards the ultimate vision of sustainable conservation agriculture solutions. Conservation Agriculture combines the following basic principles:

1. Reduction in tillage: The objective is the application of zero tillage or controlled tillage seeding systems that normally do not disturb more than 20-25% of the soil surface

2. Retention of adequate levels of crop residues and surface cover of the soil surface: The objective is to maintain an adequate soil cover through the retention of sufficient crop/cover crop residues on the soil surface to protect the soil from water/wind erosion, water run-off and evaporation to improve water productivity and to enhance soil physical, chemical and biological properties associated with long term sustainable productivity;

3. Use of crop rotations: The objective is to employ economically viable, diversified crop rotations to help moderate/mitigate possible weed, disease and pest problems and offer economically sound cropping alternatives to help minimize farmer risk.

These conservation agriculture principles seem to be applicable to a wide range of crop production systems including low-yielding, dry rain-fed as well as high-yielding irrigated conditions. However, how these principles are applied will depend on the situation and will need a flexible approach as a function of different production systems. Obviously, specific and compatible management components (weed control tactics, nutrient management strategies and appropriately-scaled implements.) will need to be identified through adaptive research with active farmer involvement to facilitate farmer adoption of appropriate CA-based technologies for contrasting agro-climatic/production systems. As such, the movement towards CA-based technologies normally is comprised of a sequence of stepwise changes in cropping system management to improve productivity and sustainability. The principles of marked tillage reductions are initially applied in combination with the retention of sufficient amounts of crop residue on the soil surface, with the assumption that appropriate crop rotations can be included or maintained to achieve an integrated, sustainable production system. Local soil and environmental conditions will determine if zero-tillage, strip tillage, permanent raised bed planting, or any other reduced tillage system is the best alternative. Local market conditions, crop production level, farming system and environment will determine the residue management strategies but with the near certainty that unless adequate residues are not retained, marked reductions in tillage will unlikely be feasible over the long term. In this paper we use the example of the irrigated wheat based systems of North Mexico as a typical case of a step-by-step process that involves the application of CA-based Resource Conserving Technologies towards the final goal of the implementation of Conservation Agriculture.

The Yaqui Valley in Sonora, Mexico

Sonora, located in the northwest of Mexico, is characterized by a desert climate, mostly sunny and dry with total amount of rainfall is about 381 mm per year with 253 mm from June to August during extreme rain events in the summer cycle (1971-2000). Average day-time temperatures during the grain filling stage are moderate (18oC) for wheat and hot (31 oC) for summer maize. Sonora has national and international importance for wheat production, especially the Yaqui Valley which forms a part of the North-West Mexican coastal plains and is located 27.33 N, 109.09 W and 38 masl (Figure 1). The valley represents a microcosm of events characterizing the progress in wheat production that has occurred around the world over the past 40 years. This valley was the center of the wheat improvement program that Dr. Norman Borlaug and his colleagues initiated in Mexico in the mid 1940s. From this modest program came the remarkable semi-dwarf wheat germplasm that dramatically increased wheat yields in Mexico, especially in irrigated areas. This material also constituted the initial introductions sent to South Asia (especially India and Pakistan) that stimulated the Green Revolution in wheat production during the mid to late 1960s. Much of the initial seed of the new, semidwarf varieties in south Asia was produced and exported by farmers in the Yaqui Valley (Sayre and Moreno-Ramos, 1997).

This valley encompasses about 255,000 ha of irrigated land using primarily gravity irrigation systems fed by canals (over 80% of irrigation water) and deep tube wells (around 20% of irrigation water). Farming is mechanized but operational farm size can range from less than 10 ha to several hundred hectares or more. Crops planted during the winter cycle are wheat (November-May), safflower (January-June), winter maize (September-February) and chickpea (December - April) while during the summer cycle summer maize (May - October), sorghum (March -July) and dry beans (March - May) are most common. (Aquino, 1998).

Four planting methods are traditionally practiced by wheat farmers in the Yaqui Valley (Aquino, 1998):

1. Melgas. This is the traditional system of planting wheat on flat seedbeds. Wheat seed is either broadcast and incorporated (generally with a harrow), or seeded with a small grain drill in rows spaced from 15 to 25 cm. Borders are raised to form the melgas (basins), the size and shape of which depend on how well the field has been levelled. The farmer can subdivide the field into straight melgas on levelled fields or into melgas that follow the contour of the land (curvas de nivel) (Figure 2).

2. Corrugations. Wheat is seeded as for melgas, either broadcast or with a small grain seeder. However, instead of raising borders, farmers make a shallow furrows spaced 70 to 90 cm apart to carry irrigation water.

3. Planting on beds. The use of a raised seed bed (60 - 90 cm) with two - four rows on the bed for wheat, one for maize and one or two for sorghum.

Figure 1. Location of the Yaqui Valley, Sonora in Mexico

Figure 2. Traditional planting in the Yaqui Valley of Sonora in melgas

4. Permanent raised beds: The use of raised bed planting systems, reshaping the original beds with only superficial soil movement in the furrows between the raised beds as needed before planting of each succeeding crop with no tillage on the surface of the beds, ideally combined with even distribution of the previous crop residues on the soil surface.

Figure 3. Conventionally tilled raised beds planted with wheat (left) and maize (right)

Conventionally Tilled and Permanent Raised Beds

Briefly, this technology consists of seeding 1-4 rows depending on the crop on the raised beds, 70-90 cm wide. Bed height is normally 15-30 cm. Irrigation water is applied to the corrugations between the beds. The system facilitates a pre-seeding irrigation to eliminate the first generation of weeds by doing shallow tillage at the time of seeding into the residual moisture. Currently most farmers use conventional tillage prior to making the beds for wheat planting; incorporating the residues of the previous crop. The system allows mechanical cultivation as an alternative method of weed control during the crop cycle including small grain crops like wheat and barley. It also makes hand weeding an economical option because of the easy field access resulting from row orientation on the beds. Irrigation water management is more efficient and less labor intensive with the use of furrows, compared to the traditional flood irrigation system.

Moreno et al. (1982) provide a brief summary of the research conducted in the Yaqui Valley to establish the basis for the raised bed planting system used on irrigated wheat in Mexico. In the early 1960s, research on the effect of different row spacing on wheat were initiated. The results showed similar yields for a wide range of spacing (from 17 to 70 cm) and demonstrated the feasibility of modifying how wheat can be planted with reduced seed rates by implementing raised bed systems. In the late 1970s a concerted effort was made to introduce and transfer this technology to farmers and the effort was successful. In 1981, only 6% of farmers in the valley were planting on beds; while by 1996 over 90% of farmers were using the system. This adoption has been paralleled by similar increases in the use of pre-seeding irrigation as an efficient part of weed control (which also ensures better stand establishment for the common heavy clay soils) and in the use of mechanical cultivation during the crop cycle for weed control (Sayre and Moreno-Ramos, 1997).

Another remarkable change in farmer practices has been the way crop residues are managed. In the 1992/93 cycle, residues from the wheat harvest were burned by 95% of the farmers and the practice was deeply entrenched. When asked how they would manage the residues from the 1993/94 cycle, 94% of farmers answered that they would continue burning it. Most respondents (75%) stated that they burn residues because of the short time available to prepare land and establish the crop for the spring-summer cycle (Aquino, 1998). In 2001, however, 96% of the farmers were no longer burning but were incorporating the residue. This is a clear example of a first step in the continuum towards sustainable systems. Conventional raised beds, however do not meet the criteria of CA but can be considered as a CA-based Resource Conserving Technology that prepares the terrain for further development to more sustainable systems.

The next step for these irrigated systems to increase sustainability was to apply the CA concepts to reduce tillage and manage crop residues on the surface by reuse of the existing raised beds with only superficial reshaping in the furrows between the raised beds as needed before planting of each succeeding crop, following even distribution of the previous crop residues (Sayre, 2004) (Figure 4). Permanent raised beds permit the implementation of crop residue strategies to maintain a permanent soil cover for greater rainwater capture and conservation.

Figure 4. Permanent raised beds planted with soybeans in remaining wheat stubble (left) and wheat planted in maize straw (right

The Scientific Base for Permanent Raised Beds

In 1991 CIMMYT and local partners showed interest in the development of permanent raised bed production technologies based on the CA principles. These would have the potential to reduce production costs, improve input-use efficiency, permit more rapid turn-around between crops and provide more sustainable soil management while still allowing the use of the existing, widespread gravity irrigation system. Therefore, a long-term experiment was initiated in 1992 in the Yaqui Valley to compare common farmer practice (based on extensive tillage to destroy the

existing raised beds with the formation of new beds for each succeeding crop), with the permanent raised bed system combined with different crop residue management options. Also several component technology trials to fine-tune different aspects of the permanent bed planting system were implemented. A detailed description of the experiments can be found in the different publications referred to below.

Crop Yields and Economic Performance with Different Long-term Bed Planting Practices

As can be observed in Figure 5, there have been large annual changes in wheat yields. Low wheat yields in 1995 and 2004 were the result of extended warm, cloudy periods during the first half of the crop cycles. However, the key outcome seen in Figure 5 is that yield differences between management treatments clearly diverged after 5 years. There were no significant wheat yield differences between any of the tillage/residue management practices for the first 5 years (10 crop cycles). However, yield differences between management treatments clearly diverged with a dramatic overall reduction in the yield for permanent beds where all residues have been routinely burned from onset of the trial, after the initial 5 years. The effect from management practices in irrigated agriculture systems (at least for tropical, semi-tropical and the warmer, temperate areas), appears to be "hidden or postponed" by the irrigation water applied until a level is reached that no longer can sustain yield even with irrigation. Research to characterize tillage and residue management issues must therefore include a time horizon at least five or more years to insure that potential differences between management practices have adequate time to be expressed. Full retention and partial retention of residues had a similar yield expression, indicating that for irrigated systems with the associated high residue yields, substantial amounts of residue probably can be removed for other economic uses without suffering a yield decline (Sayre et al., 2005).

—■—Conventional till beds - residues Incorporated —A—Permanent beds - residues burned

A Permanent beds - 70% residues removed —♦—Permanent beds - residues retained

Figure 5. The effect of tillage and residue management on wheat grain yields (kg/ha at 12% H2O), CIMMYT long-term sustainability trial on irrigated wheat systems, Yaqui Valley, Sonora, Mexico, 1993-2006 (Adapted from Sayre et al., 2005)

Although the yields of properly managed permanent beds are not markedly higher than conventionally tilled beds with residue incorporation, permanent beds production costs are markedly lower. Figure 6 illustrates the clear yield and economic advantage of permanent raised beds over conventionally tilled beds. These results are derived from a large-scale trial/farmer demonstration module where crops are planted when possible for each planting system (usually 7-10 days earlier for wheat in the permanent beds as compared to tilled beds due to faster turnaround between crops).

Similar economical benefits were observed in the summer sorghum crop planted farmer fields (Figure 7). With the conventional planting system, the minimum production of the crop to recover costs was 4.6 ton/ha while for the permanent raised beds system this point is already reached with 3.4 ton/ha. The increased production and reduced costs with permanent raised beds resulted in a cost-benefit ratio of 1.6 as opposed to 1.2 for conventionally tilled raised beds. For the marked economic advantages of the permanent raised-bed planting systems, farmers in the Yaqui Valley are now in the early stages of adopting the system (Figure 7).

A further step in implementing the CA principles is through taking advantage of the reduced turn around time between crops with reduced tillage systems and including emphasis on augmenting cropping diversity offering farmers alternative, economically viable crop rotation options. Sound crop rotations can result in positive yield

Figure 6. Comparison of average wheat grain yields, variable production costs and returns over variable costs of wheat produced with conventional tilled beds versus permanent raised beds conservation agriculture trial on irrigated wheat systems, Yaqui Valley, Sonora, Mexico, 1993-2006

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Figure 7. Comparison of cost/benefit ratio and yield required to cover cost for a sorghum summer crop with conventional tilled beds versus permanent raised beds in a farmer field of the Yaqui Valley, Sonora, Mexico

increases for the different crops in a rotation. Figure 8 shows that wheat yields are higher in systems that involve more diverse rotations, as compared to the wheat-fallow system, especially when a legume, in this case chickpeas, is included in the rotation.

Soil Quality and Soil Degradation as Influence by Different Tillage Systems

Several soil related parameters were measured in the long-term raised bed planting trial. A clear increase in stable macroaggregation was observed for permanent raised beds with residue retention compared to conventionally tilled raised beds (Table 1). Burning of residues also had a detrimental effect on soil aggregation although to a lesser extent than tillage. The effect of the decreased aggregate stability is reflected in the soil erosion by irrigation water as well as in the time-to-ponding (a rapid method to determine a soil's potential water infiltration capability). The soil loss for conventionally tilled raised beds was significantly higher compared to permanent raised beds when residues are retained (Figure 9). A longer time-to-ponding indicates that the soil has more potential infiltration ability. The time before ponding occurs is brief and very brief for tilled beds with residue incorporated and for permanent beds with the residues burned, respectively (Figure 10). However, as the level of retained residues increases with the permanent beds, time-to-ponding increases sharply, an indication that water infiltration potential also will dramatically increase. Not only is water infiltration improved, but also the soil moisture conservation in the permanent bed planning system with residue retention is better compared to conventionally tilled beds (Figure 10).

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W= Wheat; F= Fallow; S= Sorghum; M= Maize; C= Chickpea; Perm. Beds= Permanent raised beds; Conv. Beds= Conventionally tilled beds Figure 8. Effect of tillage and crop rotation on wheat grain yield averaged for 2006 and 2007 at CIMMYT long-term sustainability trial on irrigated wheat systems, Yaqui Valley, Sonora, Mexico

Table 1. Effect of tillage and crop residue management on soil properties (0-7 cm) for the CIMMYT long-term bed planting trial Sonora, Mexico (Adapted from Sayre et al., 2005; Limon-Ortega et al., 2006).

Tillage/ResidueManagement % Organic Na Aggregate Aggregate SMB C SMB N

Matter (mg kgsoil-1) Distribution Stability (mg kgsoil-1) (mg kgsoil-1)

MWD (mm) MWD (mm)

Conv. BedsResidue incorporated 1.23 564 1.32 1.262 464 4.88

Permanent BedsBurn Residue 1.32 600 0.97 1.12 465 4.46

Permanent BedsPartial Removal Residue 1.31 474 1.05 1.41 588 6.92

Permanent BedsRetain Residue 1.43 448 1.24 1.96 600 9.06

Mean 1.32 513 1.15 1.434 552 6.40

LSD (P=0.05) 0.15 53 0.22 0.33 133 1.60

MWD= Mean Weight Diameter; SMB N= Soil microbial biomass - C content; SMB N = Soil microbial biomass - N content; Conv. Beds= Conventionally tilled beds

Results of this work also indicate that the long-term use of permanent beds with all crop residues retained increases C and N from the SMB over time (Table 1). The apparent amelioration of Na levels for permanent beds with partial or full residue retention (Table 1) may have great potential for vast areas where soil salinity is an increasing problem associated with gravity-based irrigation systems (Sayre et al., 2005; Limon-Ortega et al., 2006).

Figure 9. Effect of tillage and crop residue management on soil loss (t/ha) for the CIMMYT long-term sustainability trial on irrigated wheat systems, Yaqui Valley, Sonora, Mexico

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Figure 10. Effect of tillage and crop residue management on time-to-pond for the CIMMYT long-term sustainability trial on irrigated wheat systems, Yaqui Valley, Sonora, Mexico

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Figure 11. Effect of tillage on soil moisture (mm) through the soil profile (0-60 cm) in the CIMMYT long-term sustainability trial on irrigated wheat systems, Yaqui Valley, Sonora, Mexico

Farmers Applying Permanent Raised Bed Planting in the Yaqui Valley, Sonora, Mexico

Because of the promising results of the above described trials there has been increasing interest by farmers and organizations to adopt the permanent bed technology in the Yaqui Valley of Sonora, Mexico. PIEAES, a local farmer organization, supported actively the development of an on-station farmer training module. The module is now jointly managed by the CIMMYT crop management team and PIEAES and serves as the training platform for recent new initiatives. In 2007 extension projects were started that aim at training farmers, farm managers, technicians, tractor drivers among others, in the permanent raised bed technology. Also in 2007 the Mexican Wheat Chain Organization started a progam that supported the purchase by farmer groups of CA planters.

When moving to permanent raised beds farmers have continued to use a similar sized raised beds (70 to 80 cm from furrow to furrow) in line with the bed widths that have routinely been used by farmers for conventional tilled beds. By maintaining the same bed widths that farmers are already using for tilled beds, it has been easier, whenever feasible, to modify existing implements for use with permanent beds as well as to eliminate the need to alter tractor wheel spacing already in use. The goal has been to attempt to utilize the permanent beds continuously for as long as feasible and possible.

The main factor that has limited extension and adoption of permanent raised beds (and essentially most other relevant CA technologies) in the past has been the utter lack of appropriate implements, especially seeding equipment. In many ways the development of prototype implements for seeding on permanent beds with retained residues, for band application of fertilizers on permanent beds and for maintaining the shape of the beds, has been the most important issue to confront. Therefore, the philosophy the Mexico based CIMMYT crop management team has been to develop multi-crop/multi-use implements that can be simply reconfigured to reshape beds, band apply basal or post-emerge fertilizer and seed both small and large seeded crops easily and rapidly (Figure 12).

The prototype developed has fertilizer and seed tanks with appropriate distribution mechanisms that can seed both small and large seeded crops with an acceptable level of precision using a multiple tool bar arrangement to

mount all needed attachments with adjustable clamp systems (fertilizer/seed tanks and their distribution systems, seed openers, fertilizer opens, residue management tools like discs or residue cleaners and shovels or discs for bed reshaping). The goal is to have a single implement capable of being easily and rapidly reconfigured to perform most seeding, fertilizing and bed permanent bed management activities for the crops grown by these farmers to markedly reduce the machinery costs as farmers convert from conventional, flat planting systems to permanent beds.

Figure 12. Left-Multi-crop/multi-use implement configure for reshaping permanent beds and applying basal fertilizer; Right-Same implement configured for bed reshaping, fertilizing and maize planting.

There are now irrigated permanent beds with the farmers using the multi-crop multi-use implement now commercially available in the Yaqui Valley that have supported up to 4 consecutive crops of wheat, maize and safflower but while still in a very initial stage of adoption, the area is growing. It will be of utmost importance that farmers, local organizations and scientists from all disciplines keep working together to support further extension and solve second generation problems where needed.

Conclusions

The system of raised bed planting for irrigated conditions that has been widely adopted by farmers in northwest Mexico and offers an innovative option for diversifying wheat production practices in other, similar areas around the world. Bed planting offers many advantages in irrigated production systems. The great benefit resulting from bed planting is reduced production costs, reduced irrigation water use, and marked, enhanced field access, which facilitates control of weeds and other pests, the timing and placement of nutrients, tillage reductions, and crop residue management.

The next logical step to make raised bed planting more sustainable is to reduce tillage and manage crop residues on the surface by reuse of the existing raised beds with only superficial reshaping in the furrows between the raised beds as needed following even distribution of the previous crop residues before planting each succeeding crop,. Permanent raised beds will further reduce production cost and will increase sustainability of the system through the positive effects on chemical, physical and biological soil quality. Providing farmers with viable management alternatives should be the primary role of agricultural scientists.

Acknowledgements

N.V. received a PhD fellowship of the Research Foundation - Flanders. We thank M. Ruiz Cano, J. Gutierrez Angulo, J. Sanchez Lopez, A. Zermeño, C. Rascon, B. Martínez Ortiz, A. Martinez, M. Martinez, H. González Juárez, J. Garcia Ramirez and M. Perez for technical assistance. The research was funded by the International Maize and Wheat Improvement Center (CIMMYT, Int.) and its strategic partners and donors.

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Lal, R. 1997. Residue management, conservation tillage and soil restoration for mitigating greenhouse effect by CO2-enrichment, Soil Tillage Research 43, 81-107.

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Rationale for Conservation Agriculture under Irrigated Production in

Central Asia: Lessons Learned

J.P.A. Lamers1, A. Akramhanov1, O. Egamberdiev1, A. Mossadegh-Manschadi1, M. Tursunov1, C.

Martius1' 2, R. Gupta2, 3, K. Sayre3, R. Eshchanov4 and S. Kienzler5

1 Center for Development Research (ZEF), Walter-Flex Str. 3, Bonn, 53113, Germany 2International Center for Agricultural Research in the Dry Areas (ICARDA-CAC), P.O. Box 4564 Tashkent 100000, Uzbekistan 3International Maize and Wheat Improvement Center (CIMMYT), Mexico 4Urgench State University, Khorezm, Uzbekistan 5Earth Science Faculty, Free University of Berlin

The irrigated lowlands of Central Asia have been cultivated for at least 5000 years. The large-scale mechanization, introduced during the recent Soviet-time era, provoked slowly but clearly reduced soil fertility. To revert this trend, crop management technologies that conserve natural resources are imperative. Conservation agriculture (CA) technologies, which are practiced worldwide on 95 million hectares, have been proven suitable for a wide variety of agro-ecological situations, yet mostly in rainfed areas. There various arguments to introduce CA practices also in the irrigated lowlands in Central Asia. Following a review of the current status for CA in the irrigated areas of Central Asia it is argued here that the prospects and need for CA in this region are enormous. Yet, the introduction and spread of CA practices needs to be shouldered by an awareness creation of all stakeholders including farmers, researchers, extensionists and policy makers. This necessitates in some countries legal, administrative and economic reforms. Also intensive training and education of farmers needs to be scheduled aside from the planning to ensure that the necessary agricultural equipment such as seeders and planters become available and accessible. There is also a demand for further research efforts particularly on the development of implements as well as on assessing the financial benefits from investments in CA practices. But introducing CA could alleviate the present pressure on existing land and water resources in Central Asia and reduce soil salinity which in turn could increase household income for the rural poor.

Key words: Soil degradation, salinity, water use, tillage, fuel economy, Uzbekistan

At present, already 12% (ca. 1.56 billion ha = Bha) of the global total land area of 13 Bha is used for crop cultivation, of which slightly less than 280 million ha (Mha) or 18% of the total cropland are irrigated (UNESCO-WWAP 2006, pp. 250 ff.). This amounts to a worldwide average of 0.25 ha of cropland per capita (as of 2006). In addition, an estimated 2,300 km3 water is annually used from blue (precipitation turned into freshwater in rivers and lakes) and green (precipitation stored into soil moisture and used for plant production) water sources for irrigation worldwide. While irrigated land areas increased globally from 50 Mha in 1900 to 280 Mha (2003) in about one century, in the Aral Sea Basin in Central Asia (Figure 1) an increase from 2.0 to 7.9 Mha ha irrigated cropland was reached within four decades (FAO 2000), i.e. the relative annual increase of 7.4% in the latter was almost double that of the worldwide increase of 4.6%.

About roughly 60% of the present global food production stems from rainfed cultivation, and thus ca. 40% of all foodstuffs are produced under irrigation (UNESCO-WWAP 2006), nonetheless irrigated agricultural is of paramount importance since it forms the backbone of the livelihoods in arid and semi-arid regions as well as in the humid-tropics in Southeast-Asia. Despite the high need for increasing food production worldwide, the scope for extending irrigated cropping is assessed as restricted by the limited water resources (UNESCO-WWAP 2006). This is exemplified by the situation in the Aral Sea Basin which covers most parts of the five Central Asian Republics (CARs) Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan. From the about 33 Mha of land considered suitable for irrigation, only about 3% (ca 11 Mha) are used for irrigated agriculture (Kijne 2005), for which annually 96 km3 of water are used in the basin. This underlines the importance of this relatively small irrigated area for the livelihood of 60 million people living in the CARs (Table 1). Concurrently, the increasing population increases the pressure on the natural resources, and land and water resources suffer from degradation caused by erosion, salinization, water-logging, compaction, overgrazing, and desertification. For instance, the salt-affected irrigated areas in the CARs vary between approx. 11% in the Kyrgyz Republic 50% in Uzbekistan, and up to 96% in Turkmenistan (Saigal 2003), whilst the estimated annual costs associated with desertification and land degradation for all CAR amount annually to $2.5 billion (ADB 2006). Soil organic matter (SOM) contents such as in Uzbekistan are low (Ergamberdiev, 2007).

Figure 1. Irrigated lowlands of the Aral Sea Basin comprise the regions of Surkhandarya, Kashkadarya, Samarkand, Bukhara, Khorezm and Karakalpakstan in Uzbekistan; the regions Tedjen, Mary and Dashoguz in Turkmenistan, and the downstream regions on the Syr Darya in Kazakhstan. Source: By courtesy of the University of Wuerzburg, Germany

Table 1. Selected indicators by countries

Countries Total Land, Rainfed,'000 ha Irrigated,'000 ha % Salinized of Population, Agriculture,

'000 ha (% of total land area) (% of total land area) irrigated area million % of GDP

Kazakhstan 269,970 (100) 18,994 (7.0) 3,556 (1.3) 33.0 15.1 6.5

Kyrgyzstan 19,180 (100) 238 (1.2) 1,072 (5.6) 11.5 5.1 34.1

Tajikistan 13,996 (100) 208 (1.5) 722 (5.2) 16.0 6.9 24.2

Turkmenistan 46,993 (100) 400 (0.9) 1,800 (3.8) 95.9 6.5 26.0

Uzbekistan 42,540 (100) 419 (1.0) 4,281 (10.1) 50.1 26.3 28.1

Total/Average 392,679 (100) 20,259 (5.2) 11,431 (2.9) 41.3 59.9 23.8

Source: FAOSTAT 2003

Due to the critical level of degradation of the key natural resources, there is an urgent need to alter the current soil and crop cultivation practices in favor of conservation agricultural-based practices (CA) to better sustain soil fertility and increase water use efficiency. A balanced management of these key resources should be sought by all CAR governments to better arrest the present over-exploitation of the natural resources. Although CA is known to sustain soil resources and improve their production potential by reduced tillage alone, assessment of the potential application/value of CA-based technologies has in the irrigated areas of the CAR only just begun.

Agriculture in Central Asia

During the Soviet Union (SU) era, agricultural production in the CARs was organised in large, heavily mechanised (in particular for land preparation, seeding and weed control) state (sovkhoz) and collective farms (kolkhoz). Small-scale, private, and non-mechanised farming was also practiced but mainly for domestic and household use. Agriculture was boosted in a centrally planned economy that designated CARs as suppliers of cotton fibre (especially Uzbekistan), winter wheat (particularly in the rainfed areas of Kazakhstan) and early maturing vegetables, which were exported to, and processed in other SU republics (Morgounov and Shevtsov, 2004). Hence, the state and co-operative farms were usually specialised in the production of specific commodities. For most production units the input supply and commodity marketing was heavily subsidized and centrally organized and the entire chain was oriented towards maximizing production while using high-input monocultures often of poorly adapted crops (Morgounov and Shevtsov, 2004). Important managerial decisions were taken outside the actual production units.

Following the break-up of the SU, agriculture in the CARs remains an important sector, employing over a quarter of the population and contributing, on average, about the same share to GDP (Table 1). It should be noted

that the dependence of the national economies of the CARs on agriculture has generally increased after gaining political independence in 1991, although this was related more to the demise in other sectors of the economy rather than a genuine increase in agriculture production per se (Table 2).

Table 2. Crop production in Central Asian countries in 1992 and 2005.

Major crops Kazakhstan* Kyrgyzstan Tajikistan Turkmenistan Uzbekistan

1992 2005 1992 2005 1992 2005 1992 2005 1992 2005

Cotton Area (Mha) 0.11 0.19 0.02 0.05 0.29 0.29 0.57 0.60 1.67 1.39

Yield (tha-1) 2.10 1.80 1.90 3.20 1.80 1.70 2.10 1.10 2.30 2.70

Wheat Area (Mha) 13.72 11.50 0.25 0.42 0.18 0.32 0.20 0.90 0.63 1.40

Yield (tha-1) 1.30 1.00 2.70 2.20 0.90 2.00 1.90 3.10 1.50 4.10

Rice (paddy) Area (Mha) 0.12 0.08 0.00 0.01 0.01 0.01 0.03 0.05 0.18 0.05

Yield (tha-1) 4.00 4.10 1.50 2.90 2.00 5.20 2.30 2.40 3.00 3.20

Barley Area (Mha) 5.63 1.50 0.26 0.10 0.06 0.05 0.06 0.07 0.30 0.11

Yield (tha-1) 1.50 1.00 2.40 2.10 0.80 1.30 2.10 1.00 0.90 0.90

Source: FAOSTAT 2006. * most yield data are for rainfed wheat and barley

The dominant irrigation method for crop cultivation in the CARs is furrow irrigation, characterized by relative low energy demand but high water consumption, and low efficiency (e.g., surface water irrigation has an average efficiency of 40% only; Kijne 2005; Khorst 1989). Moreover, water managers of different CARs recurrently stressed the fact of general water scarcity and considered water as the limiting factor for further expansion (Kuo et al., 2006). On the other hand, due to their irrigation water usage rates, all five CARs rank high on the list of per-capita water use in the world (WWF 2008). Irrigated crop and pasture production uses about 80% of the available water resources (in Uzbekistan even up to 95%), the remaining being allocated for industrial use and as drinking water (Horinkowa and Duchovny, 2004).

Land reforms following independence of the CARs in 1991 aimed at transforming the former state-owned kolkhozi and sovkhozi into smaller private farms. These occurred in the different CARs with different pace and intensity and in e.g. Uzbekistan has not even been completed, it resulted in various farm types (Table 3). However, the state-controlled input supply and marketing system have largely disappeared, except in the case for cotton and winter wheat in Uzbekistan and Tajikistan (Kuo et at., 2006; Spoor and Visser 2001).

The newly established private farmers face vast problems (Table 4) such as saline, polluted and degraded soils, inefficiency of irrigation water supply, and soaring machinery and fuel costs (Horinkowa and Duchovny, 2004). The resulting decline in crop yields and agricultural income threaten the farmers' livelihoods to the point that many families only survive on large remittances from family members working abroad. Money transfers from Uzbek labor migrants for instance reached 1.4 billion USD in 2006 (national scale), which was equal to 8.2% of GDP of Uzbekistan (Center for Economic Research, 2007). However, due to the worldwide crisis which also has impacted Russia and the Ukraine, much labor is force to return and transfers and cash inflow in general is expected to decrease

Why Conservation Agriculture could be Relevant to the Irrigated Areas of Central Asia?

Worldwide evidence has recurrently shown that CA could counterbalance the aspects of soil degradation and water miss-use, help producers to meet the challenge of a more efficient use land and water and derive higher incomes. To cite only one example: long-term field experiments with zero tillage under rainfed conditions in the subtropical highlands of Mexico (Govaerts et al. 2006) demonstrated the positive effects of zero-tillage, crop rotation and crop residues, compared with conventional tillage. On the other hand, there are cases where no clear benefits could be shown from CA, e.g. in Belgium (D'Haene et al., 2008, 2009 in press).

The basic components of CA are reduced tillage and field traffic in general, adequate retention of crop residues on the soil surface and the application of economically feasible and diversified crop rotations. These components are thus not site specific, but instead the most critical objectives of CA allow extending these technologies efficiently across a wide range of production conditions. CA is therefore considered an innovation process with the aim of modifying conventional crop production technologies with the use of appropriate CA implements and suitable crop cultivars and crop rotations (Gupta et al., 2007; Gupta and Seth, 2007). Although this is often referred to as minimum-till or reduced till rather than no-tillage per se.

Table 3. Overview of farm types and their characteristics in four central Asian Republics (as from 2008)

Country Farm type Ownership Number of owners Land area

Kazakhstan Household plots Private land ownership with the 1 family Small plots below 1 ha

right of inheritance

Peasant farms Private land ownership on a 2-3 families, or the Small from 7 ha and large

(individual farms) long-term rent base from 5 to largest up to 7 up to 250 ha

49 years families

Agricultural Cooperation Private land ownership on a Large number up to 2,000-14,000 ha of

long-term rent base from 49 200 members total land

to 99 years. This includes limited

liability and joint-stock companies.

Kyrgyzstan Family farms Private land ownership Single family farms. Minimum 1 ha irrigated land in

(Small-Scale individual Mainly livestock pro- mountainous, and 5 ha in non-

farms) duction mountainous areas

Peasant farms: Medium Private land ownership Several families Land area varying from

scale individual farms Importance of crops 5 to 150 ha

increases

Agricultural cooperatives Private land ownership Several households Land size varying from

or family farms that 5,000-87,0000 ha

are cooperative

members

Turkmenistan Household plots Private land ownership 1 family Small plots of about 1/4 ha and

around 15 heads of sheep

Family Farms Private land ownership 1 family Variable ranging from 3 ha

to 150 ha

Private (peasant) Mainly sheep and camel 2-3 families No arable land, no land

livestock producers producers property rights, rely on sandy

used as common rangelands

Agricultural cooperatives Practically similar to old Cooperative Large farming units operating

collective farms membership on vertical integration

Uzbekistan Dehqon farms: Private ownership with share 1 family 0,25-1 ha within the

of cooperative assets irrigated area

Individual farms for cotton Lease contracts for a maximum 1 family Following the land

and wheat production of 50 years. They can run their consolidation of November

farming business individually or 2008, 80-200 ha

if they are members of the

cooperative by taking their share

and running their own farming

Orchards and vineyards Private ownership 1 family Minimum 1 ha

Livestock farms Livestock & poultry 1 family Depending on the animal

stock. Rule is a share of 0.33

ha per cattle unit with a

minimum of 30 heads of cattle

equivalents (thus 10 ha)

In addition to the three basic tenets above, often the adequate adaption of machinery is a must for successfully implementing and adopting CA. This has occurred worldwide in tropical, subtropical and temperate regions to grow rainfed cereals, cereals between rows of perennial crops, irrigated rice-wheat systems, and development of agriculture in hillsides sloping lands. CA has steadily increased and covers nowadays about 7% of the worlds' arable land area amounting to about 95 Mha. In countries such as Paraguay, Brazil and Argentina it is now covering more than 50% of the total agricultural land. In southern Brazil, CA is practiced on nearly 90% of the arable area (Friedrich, 2007, Personal communication).

CA is not commonly practiced Central Asia, except in the rainfed areas of Kazakhstan owing to an intensive promotion from the 1960s onwards. It was meant as one avenue to reduce the massive occurring soil erosion at that

Table 4. Brief overview of agricultural characteristics inherited from the Soviet Union that persist after independence in Central Asian Republics

• Large scale area exploitation

• Monoculture on large scale collective farms with heavily mechanized production systems

• Excessive water use resulting in increasing salinization in downstream areas

• Agrarian Reforms since independence in 1991, leading to cooperative and private farming from 1994 onwards, but state production quotas remained in some CARs

• Weak financing for investments, rehabilitation, operation and maintenance

• Lack of extension and advice systems in agriculture

• Agricultural research structures and institutions dysfunctional

• Deteriorating infrastructure in irrigation and drainage network

• Inadequate agricultural equipment (as former large farms were privatized)

• Rising prices for inputs

• Declining yields, declining income, increasing poverty Source/Adapted from Horinkowa and Duchovny, 2004.

time. The concept of reduced tillage to counterbalance wind erosion had been studied intensively in rainfed areas of Northern Kazakhstan, very likely due to the harsher climate when compared to the irrigated areas in the South1. But despite the obvious benefits, CA has not spilled over to the irrigated areas of Central Asia and neither has CA figured in many research agendas for irrigated production systems, with perhaps one exception: Direct seeding of wheat into the standing cotton stubble is practiced in over 60% of the cotton-wheat growing areas in Uzbekistan in case of a delay in the cotton harvest, nevertheless showing that farmers adopt new technologies quickly when the benefits are demonstrated.

Recent results from the Indo-Gangetic Plains (IGP), which are under similar agro-ecological conditions as the CARs and where irrigated production systems also dominate, confirmed that CA technologies improve yields, reduce water consumption, and reduce negative impacts on the environmental quality also in these irrigated production systems (Gupta and Seth 2007). CA technologies were initiated in the early 1990s in the IGP but gained momentum since the late 90s when the technology became rapidly adopted by farmers. Current estimates by Gupta and Seth (2007) of winter crops planted using zero-till are as high as about 2 Mha, also caused by a research approach implemented by various international and national organizations, e.g. the Rice-Wheat Consortium. Recent findings in the northwest of Uzbekistan (Ergamberdiev 2007) showed particularly an increase in SOM with corresponding improvements in soil structure with greater soil moisture holding capacities. Most of the other benefits such as changes in soil chemical, biological and physical properties are expected to be further enhanced in the long-run. While no significant effects of reduced tillage on cotton or wheat yields could be observed in Uzbekistan, the initial yield loss that typically occurs when CA is introduced could not be observed here, while clear savings in operational costs were achieved (Tursunov 2009). Cumulative gross margin (GM) analysis showed higher gross margins in all conservation agriculture practices as compared to the control (conventional tillage). Dominance analysis revealed an advantage of the conservation practices over conventional tillage because of the lower total variable cost and higher GM (Tursunov 2009). Most of the other benefits such as changes in soil chemical, biological and physical properties are expected in the long-run.

Thus, adopting CA practices on irrigated soils of Central Asia can improve the sustainability in agricultural production and make it more profitable to farmers.

Hurdles to Master for Introducing Conservation Agriculture to Irrigated Areas in Central Asia Awareness Creation

Successful farmer adoption of CA principles may mean altering generations of traditional farming practices and implement use (from hoes to the recently introduced large-scale machineries). In Central Asia, an additional challenge is the fact that many new small and medium-scale farmers are often inexperienced former kolkhoz workers and have little experience with farming, let alone modern farming technologies. In fact, the needed change in mind set, not only by farmers but also by scientists, extension agents, private sector members and policy makers, has often represented the most difficult aspect associated with the development, transfer and adoption of CA technologies

1 Wind erosion in the irrigated areas has been combated by the establishment of an extensive network of tree windbreaks (e.g. Molchanova, 1980).

(Pieri et al., 2002a, 2002b). In many cases, it has been difficult to explain to farmers the rationale for adoption of the basic CA tenets beyond the potential to reduce production costs associated with tillage reductions (Knowler et al., 2001). As recently postulated "... it has been shown to be easier to adapt the no-tillage technology to physical conditions than to human conditions as mindset continues to be one of the biggest barriers to no-till adoption and here farmers, researchers and extensionists are included" (Derpsch, 2005).

Prior to introducing CA, the land needs to be prepared to avoid the typical initial reduction in yields (Knowler et al., 2001). This foundation can be laid by a specific cropping sequence. A transition period deems necessary to also resolve potential conflicts between the different uses of the crop residues. In many situations in the CARs, crop residues are presently used as livestock feed or burnt for cooking fuel and these uses therefore may be in conflict with field retention to provide effective soil surface mulch (Ergamberdiev 2007). Spatial factors such as available field sizes for a production of sufficient crop residues for both livestock and CA should be considered and in such cases it should also become practice that crop residue production sites must be at close distance to, or at CA areas to minimize transportation costs and that irrigation water availability is adequate.

Machinery and Equipment

Although national policies in CARs focus on agriculture, many administrators underestimate that the accessibility of locally made, appropriate CA implements has a high priority to successfully introduce CA. Farm machinery supply enterprises are mainly serviced by small and medium size private entrepreneurs (SMEs). Unfortunately, in spite of the acknowledged importance of the role of these services in the national economy, this sector is only marginally supported and motivated by governmental programs. Moreover, critical services such as for land levelling and no-till/raised bed planting are providing also employment opportunities to jobless rural youths and employment in small-scale manufacturing and transport related sectors (Gupta and Sayre, 2008). Manufacturers, importers and dealers should be proactive in increasing the demand for CA machinery and take advantage of their knowledge to ensure that they keep abreast of current advances in mechanization for CA systems, particularly in similar agro-ecosystems around the world as occur in CARs.

The key policy issue is that benefits of new technologies must reach the farmer through lower equipment and rental costs. Wherever cost of new agricultural technologies such as land levelling are extremely high, several subsidy schemes could be introduced since this practice in particular benefits the environment, save water, and improve productivity. But also seeders and planters is one of the chief requirements for the introduction of CA as it they are supposed to be suitable for the planting of crops in untilled and mulched soil and in the presence of stubbles and/or a cover crop, which at the same time protect the environment and soil properties. For example, in Uzbekistan, farmers must conduct up to five field operations to seed winter wheat into the standing cotton. First, the soil is loosened, and then the seeds are spread. Next, the seeds are buried and finally, the cotton stems are cut at ground level and removed from the fields (Tursunov 2009). Although many types of seeders are industrially produced in CARs, they have been designed mainly for sowing crops in tilled soils. Seeders for untilled soils are not commercially produced yet. The import or even the development of appropriate, multi-purpose machinery that works under the conditions of the soils in the region, as well as the cropping systems, and that allows to seed and fertilize the land at the same time, is therefore imperative (Tursunov 2009). Worldwide evidence shows that very little will happen to extend CA to farmers, especially small-scale farmers, until suitable implements are locally made and cheaply and readily available (e.g. Knowles et al. 2001).

Financial Feasibility of Conservation Agricultural Practices

The benefits of CA measures are often highlighted but dispersed widely over time. It should not be underestimated that CA also demands long-term investments (e.g. in new machinery such as direct seeders etc.), but it is unrealistic to expect that investments in a more judicious resources use will be accepted readily by farmers and land users simply because the options are better for the environment (Knowler et al., 2001). Given the present high uncertainty of marketing commodities, the general undercapitalization in rural areas, the long distances to the urban centres with potential buyers, the restrictions in input supply, obviously the farming population in the CARs is not in a position to eagerly experiment with new technologies.

Furthermore, farmers use to look for immediate and often economic benefits and are less concerned with longer-term or ecological benefits (Knowler et al., 2001). In this respect, CA like any other novel technique must clearly show economic benefits and options before farmers would consider it for adoption. This is not unique to CA,

but is overlooked often by those who emphasize the ecological side. From the standpoint of innovation, it is to be expected that economics will guide the evolution of suitable CA technologies much more than ecological benefits. Farmers may already recognize ecological problems such as advancing soil degradation or inefficient resources use, but for CA to be their solution by choice, it must provide a direct financial advantage. The recent established class of farmers in all five CARs just cannot afford risking even a temporary plunge in profitability based on recommendations that emphasize long-term economic benefits and ecological sustainability only. At present, CA technologies provide direct and immediate benefits to farmers through (i) cost-reduction incurred by lower expenses of fuel, labour, and time and (ii) yield-enhancing factors such as a reduction in soil erosion and water use effects in the short term, while improving the quality of land, water and the environment in the longer term. It should thus be ascertained that the initially mounting costs of herbicide use does not surpass the costs savings incurred by less labour, fuel and the use of equipment as well as reduced fertilizer use.

Recent financial estimates based on cumulative gross margin (GM) and dominance analyses in Uzbekistan showed higher GM with three CA practices compared to the conventional tillage as practiced by farmers (Tursunov 2009). The values were highest under intermediate tillage with crop residue retention which amounted to UZB 1,288,000 (ca. USD 1075,-) per hectare summed up) over three years. While using the results of three consecutive growing seasons, a dominance analyses showed the potential of CA over conventional practices owing to higher total variable costs and lower GM of the latter. Although these findings are encouraging, such estimates for the situation in CAR are presently too limited in numbers and need to be extended. In a recent overview on the economics of CA as practiced worldwide (Knowler et al., 2001), it was concluded that the financial profitability of CA practices varies, is thus site-specific and hence needs to be researched each time.

Training and Education

It is recurrently emphasized that the application of CA practices demands far greater managerial skills and understanding of agriculture compared to conventional cultivation practices (Knowler et al., 2001). Hence, one of the chief challenges for the introduction of CA in Central Asia is beating this lack of expertise. Organisations such as ICARDA, CIMMYT or the Tashkent Institute for Mechanization (TIM) as well as the ZEF/UNESCO Khorezm project at the University of Urgench have conducted in the past a number of workshops, seminars, conferences, and trainings which was attended by local researchers, which certainly contributed to the dissemination of information about the principles of CA (PFU 2008). However, the total number is still low, and most attendants have been researchers rather than farmers. ICARDA also published a handbook in several languages (Nurbekov 2008).

Analysis of shortcomings in agriculture in CAR emphasized numerous technical aspects, but also underlined the typical lack of managerial skills amongst the producers (Lamers et al, 2000; Lamers et al, 2008). Although land reforms and farm privatisation in the CARs aimed at boosting the agricultural sector, it established a new class of farmers who had never run a farm enterprise before. Many of them had previously been employed on former state farms, machine-tractor parks or other support organizations but not in leading positions and therefore lack the managerial skills and agronomic knowledge to adequately manage day-to-day farm operations. The low level of knowledge of the new farming generation and its governors represents major challenges in the development of the agricultural sector in CARs as to cope with shallow, saline ground water tables in particular causing secondary soil salinisation, whilst the on-going unsustainable agricultural practices enhances further soil erosion and degradation.

As with all research findings, a major challenge of CA research findings is to convert their outcomes into recommendations that fit into the production and livelihood systems. The experimental-based evidence must cope with a high measuring stick: it must be agronomic and financial superior to local practices, fit the socio-eco-nomic environment and farming systems, and should be durable. And with particular reference to CA practices, this does not require one single, standardized technology solution, but flexible rec-om-menda-tions, which allow farmers to adopt them according to their means and aims within the diversity and variability of the income generating options they pursue.

Constraints to Introduction

We currently have no information about the situation in all five CARs, but for Uzbekistan the situation is described by Schoeller-Schletter (2008) as follows: "Since Uzbekistan became independent in 1991, its legal system has been subject to frequent changes. [...] The restructuring of the agricultural sector of Uzbekistan has been accompanied by fundamental reforms in the legal framework regulating agricultural production..". Many new

laws and regulations have been introduced since independence that sometimes created conflicts of norms. Nevertheless, the state order system which still prevails in Uzbekistan e.g., is modelled on previous laws, by which the government controls cotton and wheat production. Since this includes very specific recommendations of land use, e.g. also the need for ploughing a legal framework must create an enabling environment for the employ of CA practices. Before such legal obstacles are not carefully investigated and mandated, CA with its emphasis on the reduction of tillage would find a small chance only for implementation as it would clash with legal norms.

Research Needs

Most knowledge about CA within the irrigated areas of CARs stems from very recent and actually on-going research, for which little findings have been published yet. Moreover, much of the present and on-going research has been limited to a few crops only. Despite the limited time span in which the research has been conducted, potential advantages of CA over conventional practices in cotton and wheat production have recently been summarized (see e.g. Ergamberdiev 2007; Tursunov 2009; Pulatov 2002). For instance, experiments conducted in the northwest of Uzbekistan on the dominating cotton-winter wheat rotation, was analysed for seven cropping seasons. ANOVA results showed that crop residues had a positive effect on SOM and Nitrogen contents in the topsoil, whilst soil salinity was unaffected by the soil mulch. SOM amounts were higher under zero tillage practices compared to conventional tillage (0.67 and 0.63 % respectively), whereas soil salinity was lower (0.41 and 0.47 %). Low cotton yields resulted under zero tillage but indicated PB to be the better compromise with respect to soil parameters and yields. Yet, given this recent interest only, many points of CA are still open for further research.

This concerns e.g. the adopting of the general basic tenets of CA to the local and regional conditions, which is certainly a key research challenge for the near future. Obviously, specific and compatible management components such as weed control tactics, nutrient management strategies, appropriately-scaled implements etc., will need to be developed to facilitate farmer adoption of CA in CARs. To appraise the influence of tillage and mulch treatments on soil parameter and yields adequately, the dynamics need to be studied for a longer time span than so far (Tursunov 2009), to achieve more comprehensive findings. Whereas much evidence points at the advantages of mulching and retaining crop residues, recent findings based on simulations with the soil-water model Hydrus-1D indicated that water uptake by cotton or wheat would only marginally benefit from a surface mulch layer, although it would reduce soil evaporation, capillary rise of groundwater and in turn secondary soil salinization (Forkutsa et al., forthcoming). Several aspects related to the most suitable cover crop, the retention of crop residues and in what minimum amounts, the decomposition rate and contribution of a mulch in reducing salinition and crop water demands needs to be examined and quantified.

Since one of the major constraints in the adoption of CA practices in CARs seems to be the competing interest in the use of crop residues, crop combinations have to be identified that provide both residue and fodder. Owing to a lack of adequate machinery such as tractors for plowing, crop stubbles essential for CA, are often burned, or, more commonly, removed from the field as livestock feed. This means that CA practices need to be adapted to the need of the rural population.

Also, since other innovations to enhance water and soil conservation are practiced, it may very well be that CA is perhaps not always the most beneficial option to farmers and this also needs more clarification. Since CA practices usually needs long-term commitments, the use of crop-soil simulations models has to be considered as one tool to assist in estimating the impact of management changes on crop growth and soil nutrient dynamics. For the conditions of western Uzbekistan, the model CropSyst has been parameterized and calibrated for conventional cotton and winter wheat (Sommer et al. 2008). Finally given the growing importance of livestock for household security in CARs (Iñiguez et al. 2005), also crop-livestock interactions under CA need to become subject of future research. Further research should also address incorporating the standard principles of CA to the reality of the small-scale farms and small farmers' financial possibilities and operational skills. Based on the lessons learned from elsewhere, an interaction between agricultural, soil, water and environmental research and the end-users of research findings must be considered in CARs to achieve similar results as outside the CARs.

Summary and Conclusions

The irrigated areas within Central Asia are as large 8-11 Million ha, and irrigated agriculture is key in the economy of most Central Asian Republics (CARs) (Müller 2006). Hence, the agricultural sector forms the basis for any economic progress. The advancing soil degradation and decreasing soil fertility within these irrigated areas

must be arrested within the very near future to allow for sustainable agricultural development, food security and poverty alleviation. Recent research findings demonstrated the prospects for CA in CARs. Immediate benefits include decreased soil erosion, increased water use efficiency and reduced costs for fuel and labor, whereas long-term benefits may include increased soil organic matter (SOM) and biological activity, reduced pesticide use and greenhouse gas emissions. These characteristics underline indeed the challenging potential of CA practices in CARs, but since these experiments have been few in numbers, it necessitates a cautious extrapolation of the findings to irrigated regions with similar characteristics.

The introduction and spread of CA practices needs however to be flanked by an awareness creation of farmers, researchers, extensionists and policy makers alike. The necessary change of the present resource use practices must commence, but they need to be backed up by legal, administrative and economic reform. Also training and education of farmers is compulsory in the future planning. Additional research is needed on improving implements as well as assessing the financial benefits from investments in CA practices.

Introducing CA could provide the one major avenue for bringing about important environmental and social benefits in land use systems prevailing in the CARs. By alleviating pressure on existing land and water resources and reduce soil salinity on marginal lands this could increase household income for the rural poor at the same time.

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Session 1.5: Mechanization and Energy Management

Energy Balance in Conservation Agriculture and Conventional

Farming: a Comparison

S.K. Tandon1* and Surendra Singh2

1 Assistant Director General (Engg.), Indian Council of Agricultural Research, KAB-II, New Delhi, 110 012, India 2Project Coordinator (FIM), Central Institute of Agricultural Engineering, Bhopal, 462 038, Madhya Pradesh, India

(*Email: sktandon@icar.org.in/skt4339@yahoo.com)

Paddy-Wheat is the major crop rotation adopted in Northern India and covers 12 m. ha. The mechanization of rice-wheat cropping system has provided various machines and options for tackling the challenges under different field conditions. The energy crisis of early seventies forced scientists to conserve energy in all sectors including agriculture and look for alternate source of energy. The energy use in agriculture has also increased and about 8 % of the energy is used in agriculture. Energy is used for doing various farm operations on the farm. Tillage, irrigation, harvesting, and threshing consume a large amount of energy. Hence, efforts were made to determine energy used for various farm operations and to conserve/reduce energy use on the farm by following Conservation Agriculture using no-till drills and by adoption of efficient methods of cultivation. After harvesting of paddy there is very little turn around time available for sowing wheat hence, no-till drill, strip till drill, rota till drill have been developed and were used for direct drilling of wheat in fields where paddy had been grown earlier. In conventional method, pre-sowing irrigation is applied before preparing the field using disc harrow, cultivator and planker and seed-drill is used for sowing of wheat. In minimum tillage technology, pre-sowing irrigation is avoided and no-till drill or strip-till drill or roto till druill can be used for sowing of wheat in unprepared field. Four different tillage systems were selected for the study, vis-à-vis System I (Pre-sowing irrigation + loose straw removed +disc harrow (2) + Cultivator (2) + Planker (2) + Seed-drill); System II (Pre-sowing irrigation + loose straw removed + mould board plough+disc harrow+cultivator+planker+seed-drill); System III (Loose straw removed + No-till drill) and System IV (Loose straw removed + Strip-till drill). The total energy input upto sowing including seeds and fertilizers was 11104, 10491, 8892 and 9057 MJ per hectare for systems I, II, III and IV, respectively. The total energy input was the least for system III (no-till drill), followed by system IV (strip-till drill), system I and system II. The yield was higher in systems III (5.35 t/ha) and IV (5.44 t/ha) as compared to conventional methods. System III with no-till drill and system IV with striptill drill offered advantages over system I in terms of saving in time and fuel (65-80%). The saving in cost of operation was 70-80% with No-till drill and 60-70% with Strip-till drill. In the paper the energy used for weeding, irrigation, harvesting, threshing and straw management for raising wheat have also been reported and discussed.

Keywords: Minimum tillage, zero-tillage, no-tillage, strip-till-drill, roto till drill, energy input, straw management, conservation agriculture, direct drilling

Energy consumption per unit area in agriculture is directly related with the development of technological level and production. The inputs, such as fuel, electricity, machinery, seed, fertilizer and chemical take significant share of the energy supplies to the production system in modern agriculture due to intensive cropping. Increasing demand on energy from agricultural sources has resulted in large-scale deforestation, soil erosion and loss of fertility on one hand and manifold increase in the requirement of commercial energy in the farm sector on the other. With increased uses of agriculture inputs and mechanization, the energy use in production agriculture has also increased from 5440 MJ/t in 1970 to 11391 MJ/t in 2003. The role of direct commercial energy from electricity and diesel for performing various field operations has been most prominent with 43 times increase during the period as compared to 4 times rise in indirect energy use. The fuel crisis of early seventies and increase in its price forced all countries to look for alternate sources of energy and conservation of energy in all walks of life including agriculture. Anticipating a major upward shift in the energy demand and energy use pattern in the agriculture sector, the Indian Council of Agriculture also during 1971 launched an All India Coordinated Project on "Energy Requirement in Agricultural Sector" to determine the energy use in production agriculture for raising different crops throughout the different regions of the country and to identify and suggest energy conservation techniques. The energy use for performing various operations starting from tillage, sowing, interculture, harvesting and threshing were determined and based on the study improved implements and practices were recommended. Useful information has been generated on energy use patterns for major crops in different farm categories. The results have provided a bench mark of spatial and temporal variations in the energy use patterns in Indian Agriculture. The project helped in generation of national perspective on research on energy use and management aspects of the country. The results have provided a benchmark of spatial and temporal variations in the energy use patterns in Indian agriculture.

In India, the extensive cultivation of crops to obtain higher yields has resulted in intensive resource degradation problems. For example, there is the declining water tables in the high productivity northwest irrigated region which

seriously constrain productivity and ecology. High level of fertilizer use and decreasing use efficiency are increasingly contributing to groundwater pollution and increased emission of green house gases (GHGs). High level of pesticides use in many areas has become a major health hazard. Thus, with the continuously deteriorating resources, widespread problem of water contamination and eroding ecological foundation, agriculture has become highly unsustainable and many farmers have committed suicide due to crop failure and debt. Hence, efforts have been made to conserve resources by practicing Conservation Agriculture (CA) and promoting no-tillage.

Tillage, interculture, irrigation, harvesting and threshing operations consume maximum energy. As tillage consumes maximum energy, hence, efforts were started world over in the 1970s to reduce energy use on the farm by efficiently applying different inputs and by reducing the number of tillage operations to bare minimum for seed bed preparation to get higher or equivalent yield. This led to the development of zero-till drills and gave rise to the concept of Conservation Tillage (CT) or Conservation Agriculture(CA). CA aims to achieve sustainable and profitable agriculture through the application of three CA principles; minimal soil disturbance, permanent soil cover, and crop rotation. A good number of equipment such as rotavator, laser land leveller, zero-till drill, roto-drill, strip till drill, one pass equipment, happy seeders and raised bed planter have been developed and are being propagated for CA.

Paddy and wheat are the major cereal crops of India. The well-known rice-wheat rotation covers about 37% of total area and contributes 52 percent of the country's food production. Practicing rice-wheat systems for the past several decades have however fatigued the natural resources base resulting in declining factor productivity in many areas. This cropping system is extensively adopted in Northern India. The national production of rice and wheat was 84.9 and 68.7 million tones, respectively during the year 2006-07. The mechanization of rice-wheat cropping system may provide various machines such as laser land leveler, no-till dril/strip till drill, rota-till drill, happy combo seeder, raised bed seeder, sprinklers, straw cutter cum spreader, straw baler, straw combine for conserving energy for doing various farm operations. The paper compares and discusses the energy use for doing various farm operations for rice-wheat crop rotation including farm residue management.

Energy Use in Different Farm Operations- A Comparison

Energy-use pattern in production of various crops vary due to different agronomic practices, intensity of input requirement, crop life and complexity in farm operations involved. Quantum of energy-use is also dependent on type of soil and environment made available to the plants.

Apart from technological improvement to increase energy-use efficiency, energy can also be conserved through proper application of energy-efficient implement and techniques. Energy conservation through use of agricultural machinery can be effected by employing following methods:

• Right choice of tool/implement for any operation under specific conditions

• Right combination of tools/implements

• Operating tools/implement at proper moisture

• Operating tools/implement at proper speeds

• Proper sharpening, oiling, greasing, adjustment and replacement of worn out components

Operation-wise salient energy-efficient implement/techniques suitable for cultivation of wheat crop are discussed below:

Tillage, Sowing and Planting

Tillage is one of the major farm operations and is an important contributor to the total cost of production. Excessive tillage is energy and time consuming and costly operation. Excessive tillage is considered harmful to the soil structure and It also contributes to wind and water erosion of the soil. The rising cost of hydrocarbon fuels which are bound to be exhausted sooner or later, availability of herbicides coupled with the motive of timely sowing and reducing the cost of production has provided enough incentive to the researchers all over the world to investigate tillage operations more closely. Seedbed preparatory operations are energy intensive and time consuming, exposing the cultivators to the risk of delayed sowing of crops with consequent lower yield. A one day delay in sowing wheat after optimum time results in 1 % decrease in the yield. Seedbed preparation takes about 10-30 per cent of the energy used in field operations. A number of tillage machinery (animal as well as tractor-drawn) have been developed and found to be energy-efficient for use as compared to traditional implements.

Animal-drawn Tillage Implements

Traditionally, soil stirring and mould board ploughs are used by farmers having animals as power source. The field capacity of the traditional implements is about 0.3 - 0.4 ha/day and thus work output is low. Animal-drawn disc harrows are also used for land preparation. These harrows have either four or six discs depending upon the size of draft animal available. For puddling in the rice fields, the design of disc harrow was further modified and a drum was introduced in between two discs instead of spool and known as harrow puddler . The drum limits sinkage of the discs up to 125 mm during puddling operation and thus even medium sized draught animals can pull the implement. During dry seedbed operation, the drums simultaneously break soil clods and consequently reduce the number of tillage operations. These functional advantages make the implement energy-efficient. Comparison of energy required in tillage operation using traditional animal drawn implement vis-à-vis animal drawn disc harrow-cum-puddler is indicated in Table 1. Energy required in tillage operation ranged between 328 - 362 MJ/ha by bullock-drawn disc harrow-cum-puddler for paddy and wheat crops and was about 46 to 48 per cent less than traditional implements. The difference in yield was statistically insignificant.

Table 1. Energy consumption in tillage operation on bullock farms

Crop Parameter Tillage Treatment Bullock-drawn moldboard & soil stirring plough Bullock-drawn disc harrow-cum-puddler Per cent saving over traditional method

Paddy Labour, h/ha 49.4 23.5 52.4

Pair of bullocks, h/ha 49.4 23.5 52.4

Energy in tillage, MJ/ha 611 328 46.3

Wheat Labour, h/ha 54.5 25.6 53.0

Pair of bullocks, h/ha 54.5 25.6 53.0

Energy in tillage, MJ/ha 692 362 47.7

Source: Singh et al, 1999

Tractor-drawn Tillage Implements

Tractor-drawn tyne type cultivator was widely used by the farmers for seedbed preparation and intercultural operations. Later on, tractor-drawn offset-disc harrow also became popular for better mixing of straw with soil after harvesting with combine harvester. Farmers prefer to give one or two passes of disc harrow to cut the crop residue and bury them into the soil before pre-sowing irrigation. Introduction of the above mentioned implements slowly replaced use of animal operated implements.

Promotion of use of energy efficient equipment such as rotavator, disc harrow and cultivator with pulverizing roller attachment for seedbed preparation result in fuel as well as time saving. Two to three operations of disc harrow, 3-4 operations of pulverizing roller with cultivator and 2-3 operations of planker were found optimum combination for seedbed preparation of wheat after paddy both from energy and economic return point of view. Tractor-drawn cultivators are the common tillage implements for dry and wet seedbed preparation. Every tractor owner presently has a cultivator. Farmers prefer to use offset-disc harrow after harvesting of paddy and wheat, particularly after harvesting by combine. More and more areas are coming under combine harvest. Seedbed preparation for kharif and rabi crops is becoming time consuming and consequently sowing is delayed. To reduce the number of tillage operations, save time and energy, tractor-drawn rotavator has been introduced. The use of rotavator in lieu of disc harrow for seed bed preparation saves 30-35 per cent of energy in heavier soils. Results of studies conducted on energy used in tillage for paddy and wheat crop using conventional implements (tractor-drawn disc harrow, and cultivator and improved equipment (rotavator) is indicated in Table 2. For paddy, use of rotavator required 5 per cent lower energy and 26.5 per cent less time than the conventional implement. The difference in yield under two tillage treatments was statistically insignificant. Although saving in energy with use of tractor-drawn rotavator is not significant, the amount of saving in critical operational time provides a distinct advantage.

Seedbed preparation for wheat crop by tractor-down rotavator requires 8.2 h/ha of tractor use, which is 46.7 per cent less than that required by using conventional tillage equipment. Diesel consumption by rotavator was 42.6 l/ ha, which was 31.8 per cent less than that required by tractor-drawn disc harrow and cultivator. Energy required for rotavator use was 32.4 per cent less, significantly lower compared to that required while using tractor-drawn disc

Table 2. Energy use in tillage on tractor farm

Crop Parameter Tillage Treatment Tractor-drawn disc harrow & cultivator Tractor-drawn rotavator Per cent saving over traditional method

Paddy Labour, h/ha 11.7 8.6 26.5

Tractor, h/ha 11.7 8.6 26.5

Energy in tillage, MJ/ha 3275 3106 5.2

Diesel, l/ha 54.2 51.6 4.8

Wheat Labour, h/ha 15.4 8.2 46.7

Tractor, h/ha 15.4 8.2 46.7

Energy in tillage, MJ/ha 3828 2586 32.4

Diesel, l/ha 62.5 42.6 31.8

Source: Singh et al, 1999

harrow and cultivator. No significant difference in crop yield was noticed under the two tillage treatments. Tractor-drawn rotavator is certainly a better option over combination of cultivator and disc harrow for seedbed preparation in heavier soil for wheat crop as it saves 46.7 per cent time and 31.8 per cent fuel.

Minimizing the number of tillage operations or by combining the tillage and sowing operations may also save energy in seedbed preparation and sowing. The no-till drill and strip-till drill are the machines, which does both the operations together thereby saving time and energy. Research has been conducted under the titles of minimum-tillage, no-tillage or zero tillage, optimum tillage, soil compaction, etc. Results have shown that with the development and use of appropriate herbicides, the technique of zero tillage/minimum tillage/direct drilling has shown considerable potential for some crops under certain conditions. Research conducted in the Department of Agronomy at Punjab Agricultural University, Ludhiana showed that wheat crop could be grown under minimum /no-tillage conditions without any loss in yield. However, the major handicap in the adoption of this technology was the non-availability of a suitable planting machine.

The first approach to the development of a suitable minimum till drill was to develop an appropriate attachment to an existing drill for adoption of the technology. With this end in view, five different types of commercially available seed-cum-fertilizer drills were tried for direct drilling of wheat in manually harvested paddy fields. This was intended to assess the problems arising from the use of commercially available drills under no-tillage regime. The major problems encountered were:

• Accumulation of straw and stubble in front of the tynes.

• Formation of clods

• Poor coverage of seed and fertilizer leading to bird-damage to the seeds

• Excessive slippage and lack of contact of ground wheel due to uneven fields leading to skips in the placement of seed and fertilizer

• Higher power requirement for the operation.

To overcome the above-mentioned problems, it was decided to develop a disc coulter attachment in front of furrow openers of the existing seed drill. A 9-disc coulter attachment to the existing commercial 9-row seed-cum fertilizer drill for direct drilling of wheat after paddy was designed and developed by Shukla, Tandon and Verma(1980). The performance of the zero till drill was found to be satisfactory and comparable yields were obtained under conventional tillage. The reversible furrow openers provided behind disc coulters of the no-till drill resulted in formation of clods and did not allow the seed to emerge above the surface. Hence, Tandon and Powar( 1984) replaced these reversible shovel furrow openers by boot type furrow openers with coulters fixed in front of the furrow openers for opening the slit in the soil to enable the seed and fertilizer to be placed in the soil. The modified drill was used for sowing wheat in fields where paddy had been grown earlier and in fallow land. There was not much difference in yield between zero till drilled fields and fields where one disking was done. The fallow-wheat rotation gave lowest yield. In the zero till drilled plots the incidence of weeds was less, mostly broad leaf weeds were observed and there was no incidence of philaris minor a weed which is difficult to control. Later the boot type furrow openers were replaced by inverted T-type furrow openers.

Strip-till Seed-cum-fertilizer Drill/Zero-till Drill

The drill is essentially a 9- row seed-cum-fertilizer drill with a rotary blade attachment for minimum soil manipulation running ahead of the normal furrow openers. A tractor of 35 or higher horsepower (26.11 kW) can pull it. The rotary attachment consists of a frame with a rotor having '9' flanges. Each flange has 6 C-type tines (blades). The spacing between the flanges is the same as the row spacing for the crop to be planted. Power to the rotor shaft is provided from the tractor PTO through a speed reduction gearbox and chain and sprocket drive. The rotor revolves at a speed of 300-rpm corresponding to the rated PTO speed of 540 rpm. The rotary attachment is provided with an MS sheet cover to protect the power transmission system. It also helps to reduce the soil cover over the seed. An 11-row machine is also available. Machine in double drive version is also available.

In the first phase the drill was used for planting wheat crop in heavy texture soils under paddy-wheat crop rotation (Shukla et al, 1996). Wheat variety WL-711 was sown. The experiments were conducted for four years continuously, i.e., 1985 through 1988-89 in the same field using randomized block design with three treatments (including control) and four replications. In each plot 18 rows of wheat crop were planted. The control treatment consisted of adopting standard field preparation as per recommendations of Punjab Agricultural University for raising wheat crop in heavy textured soils. These included two operations by a disk harrow, two operations by a field cultivator and three operations by a planker in manually harvested paddy field. Post emergence weed control was done mechanically with a manually operated wheel-hoe type weeder.

In treatment TI direct sowing of wheat with strip-till seed drill without any preparatory tillage was performed. Post emergence weed control was done chemically. However, in treatment T2 Post emergence weed control was done mechanically. Experimental data regarding soil moisture content at the time of sowing, fuel consumption, labour requirement, germination count and yield were taken. The field data was analyzed and found quite encouraging.

Energy input of wheat under paddy-wheat rotation in heavy soil for conventional tillage and strip-tillage was also studied from 1985-86 to 1988-89. Under the minimum tillage system, the diesel fuel consumption in planting operation only (no separate seedbed preparation required) was 18 l/ha while diesel fuel used for seedbed preparation and sowing under conventional tillage system was 60 l/ha. Thus, there was a saving of diesel to the extent of 42 l/ ha. The total energy input for minimum tillage system with mechanical weed control was 17264 MJ/ha and that with chemical weed control was 17328 MJ/ha. In conventional tillage, under similar soil conditions, the energy input varied between 19659 MJ/ha and 19723 MJ/ha. Hence, under the strip tillage system, energy saving under heavy soil condition was 2395 MJ/ha.

In the experimental results, no significant difference in the yield was observed when the crop was planted on the same day for both the conventional and strip tillage systems. However, with the strip-tillage system, a time saving of 65 to 70% in comparison with the conventional tillage planting was obtained. Thus, by adopting the strip tillage planting technology for wheat, the timeliness of operation improved significantly resulting in an increase in the total yield of wheat.

Dhaliwal (2000) conducted a study on no-till drill with inverted T-type furrow opener, no-till drill with hoe-type furrow opener, strip-till drill with shovel type furrow opener and no-till drill with double disc type furrow opener under different height of paddy stubbles for sowing of wheat crop. The suitable seeding technology for sowing wheat after paddy was strip-till drill followed by no-till drill with inverted T-type furrow opener. By using direct seeding technology, wheat sowing can also be done in time by which more area can be brought under cultivation.

Bansal (2002) conducted a study on different sowing technologies such as no-till drill with inverted T-type furrow opener and disc coulter attachment and strip-till drill under different conditions of paddy straw. The strip-till drill was found to be most suitable technology followed by no-till drill with coulter attachment and no-till drill with T-type furrow opener. Yield of wheat was significantly higher for strip-till drill under loose straw spread conditions as compared to other seeding technologies including control. The work suggests that minimum sowing technologies such as no-till drill and strip-till drill gives better results as seeds are placed at proper depth and gave better germination. Experiments were conducted in silt-clay loam soil for both the successive years 2000-01 and 200102. All the experiments were conducted after combine harvesting of paddy crop. Loose straw was manually removed from the fields. In conventional method, pre-sowing irrigation was applied before preparing the field using disc harrow x 2, cultivator x 2 and planker x 2 and seed-drill was used for sowing of the wheat. In minimum tillage technology experiments, no-till drill and strip-till drill were used for sowing of wheat crop.

Four treatments were selected during the field experiment in the successive years 2000-01 and 2001-02. The treatment are as follows:

Treatment I : Pre-sowing irrigation + loose straw removed + disc harrow (2) + Cultivator (2) + Planker (2) + Seed-drill.

Treatment II : Pre-sowing irrigation + loose straw removed + mould board plough + disc harrow + cultivator + planker + seed-drill.

Treatment III : Loose straw removed + No-till drill.

Treatment IV : Loose straw removed + Strip-till drill.

Fuel consumption for seedbed preparations was 41.05 and 30.16 l/ha in Treatment I and II respectively (Table 3). Total fuel consumption was 50.35, 39.46, 11.06 and 14.01 l/ha in Treatment I, II, III and IV respectively. Total fuel consumption was lowest in Treatment III (11.06 l/ha) followed by Treatment IV (14.01 l/ha). The saving in fuel consumption was 70-80% in Treatments III and IV over Treatment I and 60-70% over Treatment II. The sowing was done in second week of November. In case of Treatment I and II the field preparations before sowing of wheat took 10-15 days. No prior field preparations were required for Treatment III and IV. The total time required for field preparation was 13.9, 10.6, 2.7 and 3.9 h/ha respectively for Treatments I, II, III and IV.

The total energy input up to sowing including seeds and fertilizers with different systems was 11104, 10491, 8892 and 9057 MJ per hectare for Treatments I, II, III and IV respectively (Table 3). The total energy input was lower for Treatment III (no-till drill), followed by Treatment IV (strip-till drill), Treatment I and Treatment II. In the trials during successive years 2000-01 and 2001-02, the yield of wheat was maximum in case of Treatment IV (5.44 t/ha), followed by Treatment III (5.35 t/ha), Treatment I (5.16 t/ha) and Treatment II (5.04 t/ha). There was no significant difference within the replicates but the difference was significant in the yields obtained from Treatments (Table 3). Statistically the results of grain yield were found to be significant at 5% level of confidence in all treatments. The yield was significantly higher in case of Treatments III and IV as compared to system I (5.04 t/ha). Emergence of seed was better as these were placed at proper depth and soil disturbance was less in both these minimum tillage technologies. There is 33.3% saving in labour requirement, 62% saving in fuel consumption and 13.7% saving in energy requirement in field operations by use of tractor operated zero-till drill over conventional practices (Table 4).

Table 3. Details of sowing parameters and subsequent observations in the field during the year 2000-01 and 2001-02

S. No. Parameters Treatment I Treatment II Treatment III Treatment IV

1 Seed rate, kg/ha 120.7 121.4 116.0 121.3

2 Fertilizer dose, kg/ha

Urea 250 250 250 250

DAP 134.3 133 132.5 130.5

3 Depth of sowing, cm 6.7 6.6 5.3 5.7

4 Speed of operation, km/h 2.86 2.95 3.10 2.93

5 Effective field capacity, ha/h 0.41 0.38 0.38 0.27

6 Field efficiency, % 67.40 66.80 66.90 66.80

7 Fuel consumption, l/ha

a) Total tillage operations 41.05 30.16 - -

b) For sowing 9.30 9.30 11.06 14.01

c) Total system 50.35 39.46 11.06 14.01

8 Crop Yield, t/ha 5.04 5.16 5.35 5.44

9 Total energy input till sowing, MJ/ha 11104 10491 8892 9057

Source: Bansal, 2002

Table 4. Energy saving through use of no-till drill in wheat crop

Parameter Conventionalpractice No-till drill %saving

Labour requirement,man-h/ha 12 8 33.3

Fuel consumption,l/ha 31.6 12 62

Total operational energy, MJ/ha 6687 5777 13.7

A Rice-Wheat Consortium for Indo-Gangetic plain by CIMMYT, a CGIAR eco-regional initiative involving several CG Centers and National Agriculture Research System of India, Pakistan, Bangladesh and Nepal was formulated to promote resource conserving technologies such as, laser land leveller, zero-tillage, furrow irrigated bed planting system (FIRBS), surface seeding, nutrient and water management, residue management, alternative to rice-wheat cropping system in relation to CA technologies. Zero-tilled drills, strip till drills, roto till drill were used for direct drilling of wheat after paddy and their performance was compared with conventional tillage( Table 5). In these drills, the furrow openers were replaced by inverted "T- type" furrow openers. In No-till plots, fuel consumption was found to be 11.30 l/ha as compared to 34.62 l/ha by conventional method resulting in fuel saving of 23.32 l/ha. There was 67 % saving in fuel and 70 % saving in time due to no-tillage as compared to conventional method.

In other study conducted by Rautray(2003), CT as compared to conventional practice showed higher performance in terms of increased benefit cost ratio (2.47 per cent) and lower operational energy (7176 MJ/ha). The reduced tillage system lowered the cost of cultivation due to reduced energy requirement and yield returns were similar to the conventional practice as seen in Table 6. In zero tillage, the specific energy and operational energy were found to be the least (1.93 MJ/kg) as compared to other three treatments.

Table 5. Comparison of different tillage equipment used for sowing wheat after paddy

Particular No-tillage Strip tillage Seeding with Conventional tillage

seeding seeding roto —till-drill (3 passes + levelling)

Time required(h/ha) 3.23 (70.1б) 4.17(61.46) 3.45(6S.1) 10.82

Fuel used (l/ha) 11.30(67.36) 17.S0(49.45) 13.S0(60.14) 34.62

Operational energy (MJ/ha) 64S.96(67.16) 1001.76(49.31) 7S3.60(60.34) 1976.11

Cost of operation Rs/ha 639.б4(66.39) 979.95(4S.50) S07.30(57.5S) 1903.04

Figures in brackets show % of saving over conventional practice. Source: S. K. Rautray(2003)

Table 6. Comparative Performance of Zero Till Drill, Strip Till Drill, Roto Till Drill and Conventional Tillage

S.No. Particulars* Zero till drilled Strip till drilled Rota till drilled Conventional

wheat wheat wheat tillage seedling

1 Grain yield (t/ha) 3.71 3.66 3.70 3.80

2 Cost of production (Rs./ha) 9746 10328 11064 11825

3 Benefit cost ratio 2.47 2.30 2.17 2.09

4 Operational energy (MJ/ha) 7176 8604 9216 9708

б Specific operational energy (MJ/kg) 1.93 2.35 2.49 2.55

6 Specific cost of production (Rs. /kg) 2.63 2.82 2.99 3.11

Sale price of wheat Rs.6.50/ kg. Source: S. K. Rautray (2003)

The experience of zero tillage /direct drilling showed that there are many benefits in keeping the soil undistributed for long periods as nature intended. It was found that due to zero tillage, the soil drainage improves with draught cracks - worm channels - old root systems and soil pores all linking together to help to remove rain water quickly and therefore avoiding the sponge effect created by normal cultivation. Researchers found that worm population are higher and that root systems are stronger and deeper in direct drilling system. Soil structure is also improved with the organic matter being retained near the surface. This helps to improve and build up a natural surface tilth which requires little preparation for cereal sowing in addition the crumb stability or increase in soil strength.

Weeding and Interculture

Weeding is a very important operation in crop cultivation. If not done in time, the yield of the crop is reduced drastically. The average energy consumed in weeding operation for various crops is about 3 per cent. Presently weeding is practiced in four ways: i) by khurpa (a short handle tool used in squatting posture), ii) by kasola (a long handle tool used in standing posture, iii) by wheel hand hoe, and iv) by chemical weeding. It is seen that weeding by khurpa, kasola and wheel hand hoe requires 105, 75 and 24 man-h/ha respectively (Table 7). Weeding by wheel hand hoe can save 72, 61 and 67 per cent of energy over weeding by khurpa, kasola and chemical respectively without significant effect on yield. There is also a saving of 28 to 86 per cent of operational time in weeding by kasola, wheel hand hoe and chemical as compared to khurpa.

Table 7. Energy required under different weed control treatments for wheat crop

Weed control method Labour requirement Energy in weeding Saving over use of khurpa (%)

(h/ha) (MJ/ha) Time Energy

Khurpa 105 215 - -

Kasola 75 154 28.6 28.4

Wheel hand hoe 24 60 77.1 72.1

Chemical 14 183 86.7 14.9

Source: Singh et al, 1999

Irrigation

Irrigation, consumes a significant portion of total energy input for crop production, and is dependent on commercial energy sources, and energy conservation in the operation would be an effective contribution. Generally three types of irrigation methods are used:

• Flood irrigation

• Border irrigation

• Check basin irrigation

Check basin irrigation requires about 12-40 per cent lower energy as compared to other methods of irrigation without affecting the yield. Using efficient pump sets operated by electric motor and diesel engines can save considerable amount of energy. Some of the easy-to-incorporate energy-saving techniques are

• minimizing the height of delivery pipe from ground level

• use of efficient reflux valve

• use of low friction pipes

• use of large-radius bends

• proper maintenance

Irrigation is the most energy consuming operation requiring 31 % ( 1892 MJ/ha) of the operational energy. In High Yielding Zones( Punjab, Uttranchal, Western Uttar Pradesh) areas , 23 % of the tractor farms use canal water for irrigating wheat and rest use( Medium Yielding Zones- Eastern Uttar Pradesh, Maharashtra and Madhya Pradesh)ground water pumped by diesel engine/electric motor. The farms using engine used highest total energy (16311 MJ/ha) for irrigation while farms using motor used minimum energy (15096 MJ/ha)indicating variation of 8 % in energy use. Electric motor being more energy efficient than diesel, hence, farm using motor would operate with higher energy efficiency.

Studies conducted in Punjab showed that irrigation by canal saves about 100-200 % energy as compared to tubewells. Even the use of existing tubewells with proper maintenance and use of energy-efficient valves, bends etc. save about 10-15 % energy. However, irrigation energy use on zero till fields and conventional tilled fields using canal, and tubewell operated by engine and electric motor operated pumps needs to be conducted.

Harvesting and Threshing

Harvesting and threshing operation usually consumes about 25-30 per cent of operational energy used. The share varies with crop being grown. It also indicates that mechanization of the critical operations for paddy and wheat crops has increased the quantum of energy use as compared to crops like maize and cotton, which are mostly handled manually. Before introduction of high yielding varieties of paddy and wheat, harvesting and threshing were mostly done manually. After introduction of high yielding varieties of wheat, threshing operation became partly mechanized in early seventies for timely handling of large volume of crop. However, harvesting continued to be done manually. Later on animal drawn reaper was used for harvesting of paddy and wheat crops, but could not become popular because of its own limitations. Subsequently, tractor-drawn and self-propelled reapers were also developed. In mid seventies, few combines were imported and introduced in Punjab, Haryana and Western UP. Since early eighties, indigenous manufacturing of combine harvester was initiated and from mid-eighties their adoption in

Punjab started picking up for harvesting of paddy and wheat. Use of the machine has been mostly on custom hiring basis.

Harvesting by combine requires 931 MJ of energy per hectare and saves about 40 to 55 per cent of energy in harvesting over other methods of (a) manual harvesting followed by threshing by power thresher (1436 MJ/ha) and (b) using tractor-drawn reaper followed by mechanical threshing (1300 MJ/ha). Farmers commonly use a 35 hp tractor for operating mechanical thresher, which even otherwise can be operated by 7.5 to 15.0 hp diesel engine or 5 to 10 hp electric motor depending upon the capacity of thresher. Tractor engines are therefore operated on part-load with decreased fuel efficiency. There is a lot of wastage of energy only because of not using matching power source, which otherwise can be saved.

Comparison of Different Harvesting and Threshing Systems

Comparison of different harvesting and threshing systems ( System I- Manual Harvesting & Manual Threshing; System II- Tractor drawn /self propelled combine; System III - Manual Harvesting & Mechanical Threshing and System IV - Reaper Harvesting & Mechanical Threshing ) showed that the labour requirement was minimum in the case of self-propelled combine (4.5 man-h/ha) followed by tractor drawn combine (9.5 man-h/ha). The maximum labour requirement was for system 1 (230-260 man-h/ha). The grain loss in the case of system 1 was the lowest (2.15 %). The losses with combines are 4.56% for tractor drawn combine and 3.08% for self-propelled combine. These losses in combines can possibly be reduced with better adjustment and correct forward speed. The greatest advantage of combine is that the time requirement for harvesting and threshing is considerably low. Time required for tillage operation after combining is the highest as stubbles left in the field are quite large. The total operating cost was highest (Rs 3255/ha) for manual harvesting and mechanical threshing (system III) followed by reaper harvesting and mechanical threshing (system IV) Rs 2835/ha. The lowest system operating cost is for self propelled combines (system II) Rs 2545 for per ha and total system operating cost of tractor drawn combines was Rs 2775 per ha. Total system cost for manual harvesting and manual threshing (system 1) was Rs 2750/ha, if cost of grain losses is also taken into account. The total system cost was lowest in case of system II with combines if the problem of straw handling and removal is taken care of. Also, in this system labour requirement and dependence on labour was very less (<10 man-h/ha).

Straw Management

Rice-Wheat crop rotation is mostly adopted in Northern India. In India, total area under paddy and wheat cultivation was 44.3 and 25.1 million ha respectively and total production 85 million tonne and 70 million tone, respectively. This huge amount of straw is wasted annually either by burning in the fields or due to poor utilization which otherwise could contribute to the income of farmers. So there is a need to manage the paddy straw in an economically and environmentally safe way. There are three options for managing the paddy straw, these are:

• Burning the straw in the field

• Baling the straw

• Incorporation of straw in the field

Burning in Paddy Straw in Field

Burning cause loss of significant quantities of valuable biomass and also cause environmental pollution and cause many diseases. Burning of paddy straw causes a loss of about 79.38 kg/ha of nitrogen, 108.86 kg/ha of potassium and 183.71 kg/ha of phosphorus. This option is not a suitable though it is simple and adopted throughout the Northern states of India.

Bailing the Paddy Straw

In recent years, some farmers have tried to remove the straw from the field either manually or mechanically. If rice straw is not burnt then baling may provide an attractive economic environmentally safe option. Manual collection of paddy straw is a laborious job and also storing the large volume of straw is another problem. The straw can be used as dry fodder for animals. It can be used for producing electricity, in paper industry, card board industry etc. Therefore, the need of time is to find the way for manipulation of paddy straw in the field itself.

Incorporation of Paddy Straw

Paddy straw incorporation has many advantages over wheat sowing after conventional tillage. Some of them are listed as follows

• Sustain the productivity of soil as it can hold and supply the nutrients

• Environmentally safe and efficient use of natural resources

• Reduce soil erosion from water and wind

• Act as mulch and modify soil temperature

• Improve physical condition of soil

To avail the advantages there are many ways to incorporate the paddy straw in the soil. So, experiments were carried out using different technologies for paddy straw incorporation and sowing of wheat crop.

Different technologies for Straw Incorporation

Different technologies (Fig. 1) were adopted for incorporation of the paddy straw left in the field after combine harvesting. Total fuel consumption was highest in the field where straw chopper and roto-till drill (Technology V) were operated (63.51 l/ha) followed by straw chopper and strip-till drill (55.11 l/ha), Mould board plough and seed drill (49.40 l/ha), straw chopper and no-till drill (48.81 l/ha) and was lowest in the case of disc harrow and seed drill (42.88 l/ha), Table 9. The cost of total system was higher for straw chopper and roto-till drill (Rs. 3054.3/ha) followed by disc harrow and seed drill (Rs.2906.10/ha), straw chopper and strip-till drill (Rs.2652.00/ha), mould board plough and seed drill (Rs.2601.85/ha) and was lowest in case of straw chopper and no-till drill (Rs.2465.15/ha). In case of all straw incorporation treatments, germination was late than that of generally observed in non-straw incorporated fields. The weed population/m2 was higher in case of no-till drill (73.8) than other treatments. Because in sowing with no-till drill comparatively less soil was disturbed.

Figure 1. Different technologies used for incorporation of paddy straw

There was significant difference in grain yield between difference treatments. The average grain yield for technology I, technology II, technology III (no-till drill), technology IV (strip-till drill) and technology V (roto-till drill) was 5.05, 5.04, 4.83, 5.04 and 4.78 t/ha, respectively. Among different technologies used for straw incorporation and sowing of wheat in paddy harvested fields, technology I, technology II and technology III (strip-till drill) showed significantly higher grain yield as compared to technology III (no-till drill) and technology IV (roto-till drill). The technology I, technology II and technology III were at par with each other. The lower yield in case of no-till drill and roto-till drill technologies was due to repeated blockages of the machine with the chopped paddy straw during sowing of wheat. This resulted in non-uniform placement of seeds and formed patches of straw accumulation in the field, which affected the germination and thereby lowered number of tillers/m2.

Energy Requirements in Field Operations for Cultivation of Rice and Wheat in India

Under the AICRP on ERAS efforts were made to determine the energy use for rice- wheat crop rotation in different states. The energy requirement for the cultivation of rice crop in different states varied widely from 3370 MJ/ ha in Madhya Pradesh to 95758 MJ/ha in Tamil Nadu. The variation in energy requirement in different states could be attributed mainly to irrigation, which is highest in Tamil Nadu and in most cases maximum as compared to other field operations. There was wide variation in energy requirement in seedbed preparation. It was lowest in Madhya Pradesh and highest in Tamil Nadu. Similar situation exists for wheat cultivation also . Seedbed preparation, irrigation and harvesting & threshing are the three operations consuming more than 70% of energy requirements in operations. Energy requirements in seedbed preparation were lowest in Madhya Pradesh (738 MJ/ha) and highest in West Bengal (1789 MJ/ha). Energy requirements in harvesting and threshing were more in Punjab and Uttar Pradesh due to use of threshers, which are mostly operated by tractor available with the farmers.

Conclusions

From the different studies conducted by various researchers with respect to the energy use under no tillage and conventional tillage especially with respect to sowing operation have shown that no tillage results in saving in energy as compared to conventional tilled plots. Use of no tillage also results in saving in 30-40 % labour, fuel and time as compared to conventional tilled wheat. But, the energy use varies from state to sate depending upon the methods, equipment and technologies used. Some states are using more energy than required. Laser land leveler have been introduced and have been found to save 30-40 % saving in water. Hence, studies w.r.t laser leveled fields and conventional leveled fields need to be conducted. Studies by various researchers have been conducted to determine the energy use on the farm for growing wheat under different tillage systems. However, there is need to take up a large scale comprehensive study to determine the energy use in no tillage and conventional tillage for performing different farm operations by using efficient methods/equipment such as, laser land leveler for leveling the land, no till drills with self depth adjusting tynes, mechanical and chemical weed control, irrigation by canal and tubewells using motor/engine operated pumps, harvesting by reaper, combine and conventional method, threshing by motor, engine and tractor and straw management. As straw incorporation into the soil requires large amount of energy hence, most of the paddy straw is burnt causing atmospheric pollution. Studies with respect to energy use for growing wheat and other crop rotations on fields harvested by manual method, reaper, combine and different heights of the standing stubbles needs to be conducted so as to arrive at actual energy use on no till and conventional tilled fields.

References

Bansal S K (2002) Studies on the effect of direct seeding technologies on wheat crop under different paddy residue conditions. Unpublished M.Tech. Thesis, Deptt. of Farm Power and Machinery, Punjab Agricultural University, Ludhiana.

Dhaliwal I. S. (2000) Study of different seeding technologies on wheat crop under standing paddy stubble conditions. Unpublished Ph. D. Thesis, Deptt. Of Farm Power and Machinery, Punjab Agricultural University, Ludhiana.

Shukla, L.N., Tandon, S.K. & S.R. Verma. 1984. "Development and Field valuation of a Coulter Attachment for Direct Drilling". AMA, Japan, Vol.XV No.3.

Shukla L N, Chauhan A M, Dhaliwal I S and Verma S R (1996) Development of minimum till planting machinery. Agricultural Mechanization in Asia, Africa and Latin America. Vol.27 pp.15-18.

Singh Surendra, Mittal J P and Verma S R (1997) Energy requirements for production of major crops in India. Agricultural Mechanization in Asia, Africa and Latin America. Vol.28 No. 4 pp.13-17.

Singh Surendra, De Dipanker and Pannu C J S (1999) Energy Conservation Technology for farm Operations in Punjab. Technical Bulletin no. CIAE/99/73. Central Institute of Agricultural Engineering, BhopalSingh Surendra (2002) Annual report of Project, Mechanization of rice wheat cropping system for increasing the productivity" 2001-02, Deptt. of Farm Power and Machinery, Punjab Agricultural University, Ludhiana.

Tandon, S.K. & J.S. Panwar. 1985. "Studies on Reduced Tillage System for Irrigated Wheat". Proceeding of Silver Jubilee Convention, ISAE 29 31, Vol. I Farm Power & Machinery.

Tandon, S.K. and J.S. Panwar. 1987. " Potential of Energy Economy through Reduced Tillage System for Wheat (Triticum aestivum). Paper published in the Proceedings of National Conference on Energy in Agriculture and Food Processing. Indian Society of Agricultural Engineers and School of Energy Studies, Punjab Agricultural University, 30 31st October, Ludhiana.

Actual Challenges : Developing a Low Cost No-till Wheat Seeding Technologies for Heavy Residues; The Happy Seeder

H.S. Sidhu1,Yadvinder Singh1, Manpreet Singh1, J. Blackwell2, Harmanjit Singh1, Rajinder Pal Singh3

and H.S. Dhaliwal 1 and Ajaib Singh1

1 Punjab Agricultural University, Ludhiana 141 004, Punjab, India

2International Centre of WATER for Food Security, Charles Sturt University, Wagga Wagga, Australia

3Department of Primary Industries, NSW, Australia

Rice-wheat (RW) is the most popular cropping system followed on around 13.5 million ha area in the South Asia extending across the Indo-Gangetic alluvial plain. In north-western India combine harvesting of rice and wheat is now a common practice leaving large amount of crop residues in the fields. Rice straw has no economic uses and remains unutilized. To vacate fields for the timely sowing of wheat, majority of the rice straw is burnt in situ by the farmers causing environmental pollution and loss of plant nutrients and organic matter. Recently, Punjab Agricultural University, Ludhiana in collaboration with Australian Centre for International Agricultural Research has developed a new machine called 'Happy Seeder'. The Happy Seeder which needs 45 hp tractor for its working cuts, lifts and manages the standing stubble & loose straw, retaining it as surface mulch and sows wheat in a single operational pass of the field.

It is encouraging to note that about 80 ha area each in India and Pakistan have been successfully sown wheat using Happy Seeder during 2007-08 producing 5-10% more yield (with 50-60% less operational costs) compared to conventional sown wheat. Additional advantages like less weed growth, water saving, improved soil health & environment quality were also noted under the use of 'Happy Seeder' technology. Machine weight, load on the tractor and choking of machine under heavy stubble load were the major constraints in machine operation. Our objective was to develop new prototype of Happy Seeder which will work efficiently with 35hp tractors mostly available with farmers in the region. To achieve the above objective several modifications/improvements in machine design were made and tested under field conditions. These modifications included: increasing row spacing , blade geometry, blade tip speed, machine weight and rotor size/curvature to reduce the power requirement of the present machine. A light weight prototype of Happy Seeder with 30% more tip speed of modified rotor blades, 40% more window opening for easy loose straw movement and 19 % less weight has been developed having row to row spacing 25.7 cm. Replicated field experiments conducted at three locations during 2007-08 showed that row to row spacing of 30 cm out yielded the conventional 20 cm row spacing by 10 %. The detailed field evaluation of the prototype is in progress for analysing the interactive effect of variety, date of sowing and row spacing on wheat yield during 2008-09. A very dedicated and committed extension efforts & government support is required to popularize this eco-friendly technology for sustainable agriculture.

Keywords: Happy Seeder, Rice Residues, Management, Surface Mulching, Direct Drilling

Rice wheat (RW) is the major cropping system in the Indo-Gangetic Plains of South Asia grown on about 13.5 million ha each year (Timsina and Connor 2001). About 2.6 million ha are under RW system in the small state of Punjab, India alone where more than 90% of the area under rice is machine harvested leaving behind enormous quantity of residues. Rice straw is considered (excepting that from basmati variety) as of inferior feeding quality and has very limited alternative uses. Thus the majority of rice straw (about 18 million tons) is burnt in the field in Punjab, India, as this is a rapid and cheap management option, allowing for quick a turn around between crops. In addition to huge loss of plant nutrients (particularly nitrogen and sulphur) and organic matter, burning causes severe air pollution with deleterious effects on human and animal health (Bijay Singh et al. 2007, Dobermann and Fairhurst 2002). Crop residues are a renewable resource for improving soil health and are important for the sustainability of the RW eco system.

In-situ rice straw incorporation has been previously recommended as a an alternate to burning but it is practised by less than 1 % of the farmers only as it is costly and energy & time intensive. Morever, loose residues interfere with tillage and seeding operations for wheat. Developing a cost-effective technology for efficient in-situ management of this vast resource was a challenging task for the farm engineers. Minimum and zero-till technologies for wheat have been demonstrated beneficial in terms of economics, irrigation water saving and timeliness of sowing in comparison with conventional tillage (Malik et al. 2004; Humphreys et al. 2007 ; Singh et al. 2008). However, there are problems with direct drilling of wheat into combine harvested rice fields as loose straw accumulates in the seed drill furrow openers, seed metering drive wheel traction is poor due to the presence of loose straw and the depth of seed placement is non-uniform due to frequent lifting of the implement under heavy trash conditions.

Happy Seeder describes a new approach in solving the problems of direct drilling of wheat into heavy rice residues in a single operational pass while retaining the residues as surface mulch. Happy Seeder consists of a straw managing unit and a sowing unit in one composite machine. The hinged flails mounted on the rotating shaft cuts the standing stubbles and loose straw coming in front of the furrow opener with simultaneous tyne cleaning (for proper seed placement) and places the residue in between the sowing tynes. This PTO operated machine can be operated with 45 hp double clutch tractors and can cover 0.3 - 0.4 ha/hr. The Happy Seeder technology (HST) provided an alternative to burning and thus Govt of Punjab, India is encouraging adoption of this technique. The HST during 2007-08 produced 5-10% more yield (with 50-60% less operational costs) compared to conventional sown wheat. Financial analysis showed that the Happy Seeder is more profitable than the conventional alternatives, full stubble incorporation or direct drilling or rotary seeding both of which require at least partial burning whereas the Happy seeders does not require any burning of the rice residue. The study has also identified important health, community and environmental benefits from the widespread adoption of the Happy Seeder (Singh et al 2008). Additional advantages like 60-70% less weed growth, water saving (particularly pre-sowing irrigation), improved soil health (through improvements in nutrient supply capacity and soil structure) and environment quality improvement were noted for the technology (Sidhu et al 2007).

Loose straw spreading, machine weight, load on the tractor (requiring 45 hp tractor for operation) and choking of machine under heavy stubble load were the major constraints in the early machine operation. The existing machine is more expensive which is a key barrier to adoption for the poorer segment of farmers in North West India. The objective of the present study was to develop a new prototype of Happy Seeder which will work efficiently in heavy straw load with 35hp tractors mostly available with farmers in the region.

Materials and Methods

Machinery Development: Initially the furrow openers and rotor were positioned according to the normal row to row spacing of 20 cm with nine furrow openers in the machine. In 2007-08 row to row spacing was adjusted to 2040-20 cm and 30-30 cm with the hypothesis that the wider row to row spacing in wheat will compensate for low plant population with high tiller density thereby no adverse effects on yield. In order to achieve the 20-40-20 cm row geometry, alternate furrow openers and rotor blades were removed and there were only six furrow openers along the width of machine. But to achieve the 30-30 cm line spacing geometry the furrow openers and rotor was modified and adjusted in such a way that distance between the two openings was 30 cm and there were only six furrow openers along the width of machine. The power requirement of Happy Seeder was reduced by modifying the rotor and position & shape of blades (C type and Gamma type) as well as furrow openers. Fuel consumption was also monitored for two blade shapes.

Field Experiments: Three replicated field trials were conducted at PAU Ludhiana (loamy sand and sandy loam soils) and KVK, Sangrur (sandy loam), Punjab, India to evaluate the effect of row spacing on the wheat yield during 2007-08. Wheat was sown with Happy Seeder using three row spacings/geometries of 20-20 cm, 20-40-20 cm and 30-30 cm using a seed rate of 100 kg/ha. Fertilizer, weed and irrigation management practices were followed as per recommended package of practice of Punjab Agricultural University, Ludhiana (Anonymous 2008) . At sowing 60 kg/ha P2O5 ha-1 as DAP was drilled along with the seed and 35 kg N/ha as urea was broadcast before sowing. Additional 60 kg N/ha urea was top dressed 21-25 days after sowing prior to 1st irrigation. Grain yield was recorded at the time of maturity from 6 m2 area with in the each plot.

Results and Discussion

Wheat sown with a 30-30 cm row spacing yielded 10 % more compared to other row spacings/geometries (Table 1). The increase in grain yield with 30-30 cm spacing compared to the 20-20 cm and 20-40-20 cm spacing was possibly due to increase in the tillering density, grain weight and no. of grains per ear head. Based on the encouraging results from study, a light weight prototype (Figs. 1, 2 & 3) of Happy Seeder with 30% more tip speed of modified rotor blades, 40% more window opening for easy loose straw movement and 19 % less weight has been developed having row to row spacing 25.7 cm (Table 2). It was also observed that the new Gamma type blades consumed 34 % less fuel as compared to the L-type blades.

Table 1. Grain Yield (t/ha) of different row to row spacing experimental trials

Sites Soil type Straw Load Sowing date Yield (t/ha)

(t/ha) Row spacing Row spacing Row spacing

(20 cm) (20-40-20 cm) (20-40-20 cm)

1 Loamy sand 8.25 28.10.07 4.22±0.12 4.68±0.27 4.93±0.56

2 Sandy loam 8.94 6.11.07 4.89±0.30 4.47±0.24 5.21±0.14

3 Sandy loam 8.30 7.11.07 3.285±0.28 3.47±0.21 3.98±0.30

Figure 3. New prototype of Happy Seeder in operation with 35 HP tractor

Table 2. Comparison of modified prototype of HS with the existing machine

Sr. No. Specifications Happy Seeder

Happy Seeder (45 hp) New prototype (35 hp)

1 Machine function Direct drilling of wheat/ Direct drilling of wheat/

mungbean into residues. mungbean into residues.

2 Horse power required, hp 45 35

3 Flails tip speed (m/sec) at 1000 tractor engine rpm 26.98 35.07

4 Capacity, ha/h 0.26 - 0.3 0.26 - 0.3

5 Window area, m2 561 786

6 Weight, kg 625 506

7 Fuel Consumption, l/ha 16.22 11.63

8 Rotor drum diameter, mm 290 381

9 Cost, US $ 2062 1753

It is encouraging to note that area under Happy Seeder Technology has increased from 80 ha in 2007-08 to 280 ha in 2008-09 in Punjab, India. Approximately 30 machines have been sold to Government departments and Industry by three different manufacturers in the Indian Punjab. Ten field research trials for evaluating the newly developed Happy Seeder (35 hp model, 25.7 cm row to row spacing) are in progress at different locations in Punjab, India during the 2008-09 wheat season. Three replicated trials to study the interaction effect of date of sowing, wheat variety and row to row spacing are also in progress during current wheat sowing season.

Constraints and Challenges

The constraint and challenges related to HST which include uniform spreading of loose rice straw in the combine harvested fields before using the machine, damage of germinating wheat seedlings by rodents and the difficulty of forming bunds in uncultivated fields in the presence of rice residue, are being addressed. A mechanical device attached to the combine harvester has been developed and tested under field conditions for uniform spreading of rice straw in combine harvested fields. Use of the spreader attached with the combine harvester will enable harvesting of rice and sowing of wheat using HST on the same day in the residual soil moisture thus saving the use of precious water for pre-sowing irrigation. A simple and cost effective technology is already in place to control rodents in the wheat fields (Anonymous 2008). Similarly, a tractor-drawn disc bund maker is available to prepare bunds in wheat fields with heavy straw loads. Training of contractors and technical staff is essential for proper operation and maintenance of machine. The involvement of contractors is also important to enable farmers with small holdings to be able to have access to the technology without having to buy the costly Happy Seeder planters (US $ 1753) of their own. A highly dedicated and committed extension effort along with sincere government support are required to popularize this eco-friendly technology for sustainable agriculture on large areas under RW system.

References

Anonymous (2008) Package of practice for Rabi crops of Punjab. Punjab Agricultural University,Ludhiana, India

Dobermann A and Fairhurst T H (2002) Rice straw management. Better Crops International Vol. 16,May Special Supplement.

Humphreys E., Masih I., Kukal S.S., Turral H. and Sikka A. (2007). Increasing field scale water productivity of rice-wheat systems in the Indo-gangetic Basin. In "Proceedings of the International Rice Congress", New Delhi, 9-13 October 2006.

Malik R.K.and Yadav A., Gill G.S., Sardana P., Gupta R.K. and Piggin C. (2004). Evolution and acceleration of no-till farming in rice-wheat cropping system of the Indo-Gangetic Plains. In 'New directions for a diverse planet', Proceedings of the 4th International Crop Science Congress, Brisbane, 29 September-3 October 2004. At<http:www.cropscience.org.au/icsc2004/symposia/2/2/ 459_malikrk.htm>. Accessed 9 May 2006.

Sidhu H.S., Manpreet Singh, Humphreys E., Yadvinder Singh and Sarbjeet Singh Sidhu (2007). The Happy Seeder enables direct drilling of wheat into rice stubble Australian Journal of Experimental Agriculture, 2007, 47, 844-854

Singh Bijay, Shan Y. H., Johnson-Beebout S. E., Singh Yadvinder, and Buresh R. J. (2007) Crop Residue Management for Lowland Rice-Based Cropping Systems in Asia , Advances in Agronomy, Volume 98 ; 118-186.

Singh R.P., Dhaliwal H.S., Tejpal Singh, Sidhu H S, Yadvinder Singh and Humphreys E. (2008). Afinancial assessment of the Happy Seeder technology for rice-wheat systems in Punjab, India pp-182-190. In "Permanent beds and rice residue management for rice-wheat systems in the Indo-Gangetic Plain" ed. by E. Humphreys and C. Roth, ACIAR proceedings No. 127.

Timsina J. and Connor D.J. 2001. Productivity and management of rice-wheat cropping systems; issues and challenges. Field Crops Research 69, 93-132.

Actual Challenges: Developing Low Cost No-Till Seeding Technologies for Heavy Residues; Small-Scale No-Till Seeders for

Two Wheel Tractors

Israil Hossain1; R. Jeff Esdaile2, Richard Bell3; Chris Holland4; Enamul Haque5,

Ken Sayre6 and M Alam7

Senior Scientific Officer (Ag Engineer), Wheat Research Centre, Dinajpur, Bangladesh, email:

<mdisrail@gmail. com> Agricultural Consultant, ACIAR Project Australia email: rjesdaile@bigpond.com 3Professor, Murdoch University, W. Australia, rbell@murdoch.edu.au 4Principal, Spring Ridge Engineering, Spring Ridge 2343 NSW Australia 56&7Senior Program Manager and Agronomists, CIMMYT Bangladesh , CIMMYT Mexico and IRRI

Bangladesh, respectively

Small farmers from South Asia and other parts of the world use two wheel tractors as the main means of land preparation and other farm operations due to small farm and field size combined with an affordable price. These units have become very popular, and over 500,000 are manufactured annually worldwide. There are over 350,000 operating in Bangladesh alone. Two low cost and robust no-till seeders to suit two wheel tractors (12HP) have been developed at the Wheat Research Centre (WRC), Dinajpur, Bangladesh (with support from the Australian Centre for International Agricultural Research). This follows initial research and development work assisted by CIMMYT and Bangladesh Agricultural Research Institute from 1995 to 2004.

A. No till seed drill

This drill is structurally improved, lighter and more versatile than the original prototype. A fertiliser attachment has now been fitted, residue clearance is improved, and the seed drill is easily adjustable for tine layout, row spacing, and depth of seeding. Seed and fertiliser rates are easily adjusted and the machine can conveniently meter all seed sizes from maize to mustard. Press wheels have also been fitted. Attachment hitches for both Chinese made, as well as Thai made two wheel tractors are available.

B. Modified rotary tillage seed drill

This standard rotary tillage drill has been modified by the provision of a fertiliser attachment and an improved seed metering system. Seed placement has been enhanced by the incorporation of superior tine openers. Press wheels have also been fitted. It can be used as a 100% tillage implement, or as a strip tillage seed drill.

The no till seed drill has been intensively tested in farmer's fields in NW Bangladesh for wheat, maize, pulses and rice planting through moderate densities of cereal residues without plugging. Two wheel tractors can pull 4 tines in light soils and 3 tines in heavy soils. It has generally performed well. However, it has done a mediocre job in some hard setting clay soils.

The rotary tillage drill in either strip or full tillage mode has proved to be successful under practically all conditions in Bangladesh. This seed drill generally produces a satisfactory environment for crop establishment, with good seed placement and a fine tilth of soil, except under very wet conditions, when slot smearing by the tractor blades still occurs. Both implements are suitable for traditional or conservation farming systems. Seed placement and depth control in both machines is greatly improved, by the provision of superior tines and press wheels. Plant establishment has improved by17-25% compared to zero press wheel treatments. The seeders are simple, light in weight, and could be fabricated by local farm machinery manufacturers. Costs are expected to be < US$500 once production scales up.

Key words: Two wheel tractor, zero tillage, strip tillage, seed drill, rotary seed drill

Small farmers from South Asia, and other parts of the world use the power tiller (two wheel tractor) as the main means of traction for tillage and other farm operations. These units have become very popular, and over 500,000 are manufactured annually worldwide. There are over 350,000 operating in Bangladesh alone (Alam et al.,2007).

Many small farmers in South Asia are aware of the benefits of conservation farming systems including minimum and zero tillage. However they lack the means to put into action these farming systems due to the unavailability of a suitable seed drill.

The benefits of conservation farming systems are well known, and this system of farming has reached an advanced stage in many parts of the world. However the equipment to put this into practice has been principally designed for traditional four wheeled tractors and there are no commercially available conservation farming implements

(principally seed drills) for two wheel tractor. Late planting is one of the main constraints to successful crop production in this region. Saunders (1988) reported that a linear decline in yield of 1-1.5% per day was observed when wheat was planted after the end of November irrespective of short or medium duration varieties. In this case increased nitrogen applications can not compensate for the decline in yield from late planting. Zero tillage option increases the water and nutrient use efficiency by allowing timely planting and producing high yields (Hobbs, 2003).

Haque et al (2004) reported on the fabrication and testing of a power tiller operated zero tillage seed drill in Bangladesh. The development and testing of a prototype was conducted between 1999 and 2004. Results indicated a cost saving of 83-89% over the traditional tillage system, and a time saving of 10-15 days, when planting rabi crops into aman rice residue in October/November. The research was funded by USAID, FAO and carried out by WRC, CIMMYT Bangladesh. However funding ceased in 2004, and no commercially available implement has been produced.

Justice et al (2004) also reported on an associated project in Bangladesh where a commercially available Chinese Power Tiller Operated Seeder (PTOS) was modified for strip tillage. This also was used to plant rabi crops into aman rice residue in October/November. One pass full tillage was compared to strip tillage. In the strip tillage treatment, half of the tiller blades were removed and the seeds placed into the tilled strips. Field capacity of the seed drill was increased by 25%, fuel consumption was reduced by 20% and planting cost reduced by 8% compared to the full tillage treatment. Adoption of the power tiller operated rotary tillage seed drill has been more successful and 400 units were sold in Bangladesh between 2005 and 2007. However ongoing research into this planting system also ceased in 2004.

In 2006 the authors realised that the ongoing research and development of seed drills for two wheel tractor was effectively at a standstill. Also we realised that this technology, although developed for Bangladesh, could also be applied to other South Asian countries where two wheel tractors is the main farm traction unit (East India, Cambodia, Laos PDR, Vietnam, Indonesia, and Mainland China).

Materials and Methods

In mid 2007, application was made to the Australian Centre for International Agricultural Research (ACIAR) who agreed to fund a continuation of this research work. An original Wheat Research Centre (WRC) made zero till (ZT) drill, and a standard rotary drill were modified in Bangladesh in late 2007 at WRC, Dinajpur and field work with these units commenced in November 2007. In addition, A Chinese made (Dong Feng brand, 12Hp) two wheel tractor was imported into Australia in early 2008, along with a rotary drill. This tractor and seed drill was used as the test modules for further prototype seed drill fabrication. Improved examples of the two seed drill types were fabricated at Spring Ridge Engineering using local expertise. This experience has been acquired in the manufacture of larger zero tillage seed drills in Australia. They are as follows:

Tined Type Zero Till Drill. (Tool bar mounted)

This implement is essentially an improved model of the original tined type ZT drill as described by Haque et al (2004). A much improved three bar tool bar frame that is 1000mm. wide has been made up from 50mm x 4mm thick square tube. There are two side rails, of 75mm wide x 10mm thick x 825 mm long flat steel. Holes have been drilled in the side rails every 90mm. The tool bars can be fitted at various points to allow adjustable bar spacing. The resultant frame can be set up as a one bar, two bar, or three bar implement at bar spacings of up to 700mm.

Up to four tines can be fitted to the tool bar. The tines are made of 50mm x 12mm high tensile steel. Each tine is 700mm long, and is fitted with a non-detachable point (which is tungsten tipped) and a seed tube. Each tine is in a holding bracket and is clamped to the bar by 50mm square "U" bolts. Tines can be adjusted both vertically and laterally along the bars. Mounted 250mm diameter x 50mm wide press wheels are fitted to a 25mm axle at the rear of the implement. Press wheel spacing is adjustable, and the number of press wheels can be varied to suit the number of tines being used for sowing.

Dual two row bi-compartment boxes are fitted, with the front compartments for seed, and the rears for fertiliser. In order to ensure good seed drop, and allow good clearance for the tines and tool bar, the boxes are mounted either side of the handlebars of the tractor. Box position is adjustable vertically and laterally to allow for suitable fitting to different types of two wheel tractor. Fig.1 shows the two wheel tractor zero till drill.

The front box is fitted with Asian made dual system fluted roller seed meters. These meters can measure out seed of all sizes from maize to mustard at variable rates. A second set of fluted roller meters in the rear box. These meters deliver fertiliser also at variable rate as required. Toolbar frame also facilitated fixing different type of seed metering devices and other implements.

Drive to the seed and fertiliser boxes is by a chain drive, from the main drive wheel of the tractor intermediate shaft above the front bar and hitch. A clutch is fitted to the intermediate shaft. External chains then drive to the metering shafts.

Modification to Rotary Tillage Seed Drill

In the standard commercially available arrangement this Asian made seed drill is set up for one pass seeding with 100% rotary tillage. The seed box is set up above the tillage unit, and the seed delivered by tubes and lightweight soil openers to the soil immediately behind the tilled zone. A steel long roller then lightly firms the soil behind the seed drill. No fertiliser box is available.

The authors noted that seed positioning into the tilled soil behind the unit was poor. Some seeds were on the soil surface, some at intermediate positions in the tilled zone, and some were at the bottom of the tilled layer. Seed pressing was also poor. This setup may be satisfactory in optimum moist soils, or where the new crop is to be 'watered up' by irrigation, or where follow up rain to germinate the seeds is assured. However in dry soils, or rabi crop planting with no follow-up rain, seed placement is unsatisfactory.

Fertiliser application is by a separate operation, and fertiliser cannot be positioned in the seed row with the seed. The seed box was removed and an add-on tool bar, the width of the tiller (1200 mm.) was made up. This tool bar is also of 50mm x 50mm x 4mm square bar, with similar tines to the tined unit described earlier. The bar is positioned immediately above and behind the tiller. It is attached to the main frame of the tiller. Tine type openers are positioned so that all the seeds can be delivered to the bottom of the tilled layer, and into the untilled subsoil if required. Fig. 2 shows the rotary till drill. The steel roller was removed, and replaced by a 25mm axle with press wheels similar to the tined unit.

Figure 1. Two wheel tractor zero till drill Figure 2. Two wheel tractor driven strip till drill

Seed and fertiliser boxes similar to the boxes used on the no till drill are fitted. Drive from the two wheel tractor axle, through an intermediate shaft is similar to the no till drill.

General Field Performance

A prototype of each of the Australian made ZT drill and the rotary drill modification were sent to Bangladesh in mid 2008. They are currently undergoing exhaustive evaluation behind a Chinese made (Dong Feng) two wheel tractor.

The ZT drill generally has excellent penetration when used for rabi planting in Bangladesh. The 12HP two wheel tractors will pull three tines in the sandy loam soils of NW Bangladesh under most conditions. It will also operate three tines in the clay soils of the Barind High Tract under ideal conditions. However in clay soils when the topsoil is dry and the moist soil layer is at 8-10cm. a 12HP tractor could not operate three tines, and there was excessive wheel slip and vibration.

Many of the clay soils of the Barind High Tract are poorly structured, and when the tined seed drill is operated, the topsoil breaks into large dry clods. Seed cover and pressing under these conditions is poor. There has also been some slot smearing in clay soils under wetter than ideal conditions.

The modified rotary drill has proved to be successful under practically all conditions in Bangladesh. This seed drill generally produces a satisfactory environment for crop establishment, with good seed placement at the bottom of the slots and a fine tilth of soil over the seeds, except under very wet conditions, when slot smearing by the tractor blades still occurs. It has been evaluated as a 100% tillage unit, or as a strip tillage machine. In strip tillage mode, strip widths from 20-50mm. have been tried, with the narrow strip system disturbing less soil. However depending on tractor blade shape and slot width, some disturbed soil from the strips is thrown into the inter-row spaces, and this sometimes results in insufficient cover for the sown seeds in the seed rows.

With both drills the addition of press wheels has been very positive. Loose disturbed soil is considerably compacted over the seeds in the planted rows. Increases in crop establishment rates have been observed. The two wheel tractor driven zero till drill has been evaluated by stress analysis and computer simulation and found to be structurally adequate for the tasks for which it was designed (Fraser, 2008).

Results and Discussion

Data from the last three years using the old version zero till drill, and earlier versions of the modified rotary tillage drill as well as the latest models have been summarised and are presented below. Field performance of the ZT drill for wheat, maize, mungbean establishment and comparisons with the standard tillage system in several farmers fields indicate that wheat can be established immediately after rice using the ZT planter. Data is shown in Table 1. Soil moisture content is the key factor for utilization of ZT machine. It is very difficult to operate drill over soil moisture 35% due to excessive tiller wheel slippage. Effective field capacity of the drill for wheat, maize and mungbean planting is shown. The effective field capacity for maize planting was higher than wheat planting due to wider sowing width in maize planting of 1.30 m ( 2 lines spacing 65 cm) but in wheat seeding it was 80cm. Fuel consumption figures are also shown. Field efficiency during maize planting 75% which was comparatively lower than wheat and mungbean planting due to more time loss with adjustments.

Table 1. Field performance of power tiller operated ZT planter

Sl No. Parameters Wheat Maize Mungbean

1 Fuel consumption, lit./hr 1.20 1.2 1.2

2 Speed of operation, km/hr 2.50 2.5 2.5

3 Soil moisture content, % 24 27 25

4 Effective field capacity, ha/hr 0.15 0. 20 0.20

5 Field efficiency, % 75 75 75

Crop performance of the ZT planter is shown in Table 2. Originally the persian wheel type seed metering device was used, but this has now been replaced with the dual system fluted roller meters of Chinese origin. The average widths of opening slots are shown. It was found that slower speed is comparatively better for seed placement into the slots. The adjustment of row spacing between two successive passes depends on operator skill and experiences. The width of slot during maize sowing was bigger due to the slightly deeper position of the opener. No till seed drill minimized turn around time 10-12 days between the two crops. Farmer can establish crops utilizing the residual soil moisture without extra land preparation. As no need pre irrigation, that means water, electricity, diesel fuel and valuable time to be saved.

Table 2. Crop performance on zero tillage

Sl No Parameter Wheat Maize Mungbean

1 Variety Prodip NK 40 BARI Mug-6

2 Seed rate, kg/ha 120 20 20

3 Row to row spacing, cm 20 65 30

4 Depth of planting, cm 3-4 4-5 3-4

5 Width of opening slots, cm 2-3 2.5-3.5 2-3

Table 3 shows the variations of seeding depth and plant population with and without press wheels. Press wheels cover the seeding line which ensures superior seed/soil contact. In the zero press wheel seeded plot direct sunlight and bird damage also contributed to lower establishment. Similarly, in maize and mungbean plots, plant populations in press wheel plot were higher than without press wheel plots.

Table 3. Effect of press wheels on plant stand

Sl Name of crop Seed germination, Seeding depth, mm Plant population/m2 (CV %)

No. % (+) Press wheel (-) Press wheel (+) Press wheel (-) Press wheel % Increase

1 2 3 Wheat Maize Mungbean 95 90 93 30 20-25 40 25-40 30 30 265 (8) 206 (10) 22 12(7) 10 (11) 17 32(12) 24 (12) 25

The yield of wheat, mungbean and rice in ZT system and conventional method is presented in Table 4. The yield of wheat in zero till method varies from place to place due to land type, soil moisture and weed management. The average wheat yield was found 3.8 t/ha which was 21% higher than conventional method. Mungbean and maize yield were 0.9 t/ha and 8.4t/ha respectively. Maize yield was statistically similar with conventional method. Immediate after T. aman harvest, there was less weed burden and the land was suitable for zero till wheat cultivation. Mungbean was planted immediate after wheat harvest (April 1st week). Planting date should be within March for better crop yield and management. Generally farmers in this area do not grow mungbean conventionally, but plenty of wheat land remains fallow up to T. aman planting June -July and a mungbean cop can conveniently be planted by ZT methods. It was found that BARI mung-6 performed well within this fallow period. It can be harvested within 60-63 days. Last three years demonstration, farmers reported that yield of Aman rice increased average 10-15% over non mungbean planted field. There was a great potential to fit mungeban in rice-wheat cropping system reducing the turn around time. It was also critically observed that zero till wheat was less lodge compare to conventional planted wheat. It was due to not much loose soil as conventional till soil. Three crops can be fitted within a year utilizing the efficient performance of the drill.

Table 4. Comparison of yield between zero tillage and conventional method

Sl No. Planting system Yield (t/ha) (CV%)

Wheat Mungbean Maize

1 Zero tillage system 3.8 (12) 0.90 (13) 8.4(10)

2 Conventional method 3.0 (14) 0.55 (11) 7.6 (14)

Planting cost of wheat, mungbean and maize in zero till with conventional method were presented in Table 5. Planting cost of wheat, mungbean and maize in zero till system were Tk. 1951.27, Tk.1576 and Tk.1576.0/ha, respectively. Similarly wheat and maize planting costs were Tk.3740.0 and Tk.7250.0/ha respectively. The planting cost of wheat and maize in zero tillage planters were 48% and 78% less than that of conventional planting method. The cause of variation of planting cost in different crops was different effective field capacity during operation.

Table 5. Comparison of cost (1US$=Tk.69.0) of planting by zero tillage and conventional system

Sl No. Planting system Cost of planting (Tk./ha)

Wheat Mungbean Maize

1 Zero tillage system 1951.0 1576.0 1576.0

2 Conventional method 3740.0 3740.0 7250.0

Farmers are getting more interest using no till drill considering less cost involvement and less effort on seed sowing.

Beak-even use of the zero till drill was shown in Fig.3 and it wascalculated on the basis of fixed cost and variable cost of the drill considering purchase price, interest on investment, and machine life according to Hunt (1995). It was observed that cost per hectare decreased with the increasing of land area use annually. Break even use of zero till drill was found 6.5 ha which indicated that it was the point where no loss no profit. An owner must plan for profitable use of the drill over 6.5 ha land annually.

Lantf us«,

Figure 3. Break even point of zero till drill

Conclusions

The authors consider that these two seed drills have considerable potential to greatly increase productivity in South Asia, and other countries of the world where the two wheel tractor is the main traction unit in farming.

The main task now is to promote this technology and have these drills readily available to farmers at an affordable price. The zero till drill can be readily made from local components in most workshops. Most of the steel for fabrication is simple in design, and tines can be made from old automotive leaf springs. The only specialised items required are the seed meters, which sourced at an inexpensive price from a Chinese manufacturer or local promoter.

The modification to the rotary tillage drill is one which we believe should be seriously considered by the Asian manufacturers of this unit.

Further Work

Zero Till Drill

Although the power tiller ZT seed drill generally operates well, there are avenues for further research that could be contemplated. These include:

• Varying press wheel materials, weight, and profiles to suit different soil types and conditions.

• Different point types on the tines to suit different soil types and cultural operations. (This implement can also be set up as an inter-row cultivator)

• Design and fabrication of a mounted boom spray for power tiller using the seed drill frame.

• The design and fabrication of a small land leveller/road grader for two wheel tractor.

Strip Till Drill

This drill, both in 100% tillage and strip tillage modes is more suited to clay soils which are hard and dry on the surface. The action of the rotary blades pulverises the soil and clods, and there are more small aggregates available in the seed zone for better seed cover and pressing.

• However depending on tractor blade shape and position, some soil is thrown out of the tilled slots and into the inter-row spaces and this can result in insufficient soil being available for adequate seed cover. Further work on the development of shielding to alleviate this problem has commenced.

• Tractor blade shape and seed position can also affect vibration throughout the whole machine as well as the overall quality of the seeding operation. Re-arrangement of blade position and number as described by Lee et al (2003) could be a fruitful area of further development of this seed drill.

• In the author's opinion, both seed drills also have potential for direct seeding of rice at the beginning of the monsoon (kharif) season. This could be the subject of further work.

• Both seed drills, with little modification, can be used in bed planting systems.

• The disc opener options have not yet been tested in Asia. (However they may be unaffordable to most small farmers).

• One each of the tined drill prototype has also been sent to Cambodia and Lao PDR. These are being evaluated behind a Thai built (Siam Kubota) two wheel tractor. A rotary tillage option is not readily available for Thai built two wheel tractor and thus the strip tillage unit is not being considered in these countries.

Acknowledgements

The authors gratefully acknowledge the support of the Australian Centre for International Agricultural Research

(ACIAR) who has funded the work.. The authors also acknowledge the contribution of Dr. Craig Meisner, Dr. Peter

Hobbs, Mr. Scott Justice and R.Gupta who devised the original concepts and did the original development work.

References

Alam, M.M.; M.A.Satter; M.O. Faruque; M.S.Hasan and Chowdhury M.G.R..2007. Manufacturing of agricultural machinery: It's problems, prospects and quality assurance. Proceedings of the national workshop on strengthening agricultural mechanization: policies and implementation strategies in Bangladesh held at Dhaka on 11 June 2007.

Fraser M.J. 2008. Development of a No-till toolbar for a two wheeled power tiller. Bachelor of Engineering project thesis. Univ. of Southern Qld. Toowoomba, Australia.

Haque E.M., Meisner C.A., Hossain I., Justice C., Sayre K. 2004. Two-Wheel Tractor Operated Seed Drill: A Viable Crop Establishment and Resource Conservation Option. Proc.Int. Conf.' Beijing Sponsored by CIGR, CSAM and CSAE Beijing, China 11- 14 October 2004.

Hobbs,P. 2003. Problems addressed by reduced and zero-tillage and bed planting. Addressing resource conservation issues in Rice-Wheat systems of South Asia. A resource book.pp113-114.

Hunt, D. 1995.Farm Power and Machinery Management . Cost Determination. 9th Edition, Iowa State University Press, America..

Justice, S., Haque E.M.,. Meisner C.A., Hossain I., Ganesh Sah, Tripathi, J, Rashid, M.H. Amin, M.R.. 2004.Giving South Asia Farmers a Choice: A Single Drill for Reduced and Strip Till Crops for 2-Wheel Tractors", Proc.Int Conf.' Beijing Sponsored by CIGR, CSAM and CSAE Beijing, China 11-14 October2004.

Lee, K. S., Park S. H., Park W.Y., and. Lee C. S. 2003. Strip tillage characteristics of rotary tiller blades for use in a dry land direct rice seeder Soil and Tillage Research 71 (1) pp 25-32.

Saunders, D.A.1988. Crop management research: Summery of results, Monograph No.5: Wheat Research Centre, Dinajpur, Bangladesh.

Research and Development of Light No-till Seeders in China

Li Hongwen, Wang Qingjie, Wang Xiaoyan, He Jin, Gao Huanwen, Li Wenying

China Agricultural Unviersity, Beijing, 100083, China (Email: lhwen@cau.edu.cn)

The adoption of conservation tillage in China, particularly in dry-land farming areas of Northern China, has significant resource, environmental and economic benefits. However, no-tillage seeding in heavy residue cover field is the main limiting factor for the application and extension of conservation tillage in China. Some foreign no-till seeders have strong anti-blockage ability, but they are heavy (765-1130kg/m) and expensive. From 1992, we started the research on lighter and cheaper no-till seeder. These no-tillage seeders with 316-500kg/m of unit weight (50% of foreign seeders) are suitable for Chinese small and middle size tractor (500-650kg/m), while the prices are only 10-15% of foreign no-tillage wheat seeders.

Key words: No-till Seeders, Light-size, Active Anti-blockage, Passive Anti-blockage

Wheat and corn no-till seeders play an important role in the application and extension of conservation tillage. However, due to the unsound implements, especially undeveloped no-till seeders, although we've started conservation tillage research since 1960s, it hasn't yet been widely applied till 1990s. Admittedly, oversea no-till seeders are qualified enough and backed with complete development and large application, but they could only match with large-sized tractors and travel on massive fields. Besides, heavy weight and high price can also lead to the incompatibility with restrictions of mini-sized fields, small tractors and impoverished farmers in China. Therefore, we have to self-develop light no-till seeders particularly suitable to Chinese requirements [1].

The main task of designing no-till seeders is to handle crop straw, namely anti-blockage. Actually, compared with heavy seeders, light seeders are less likely to pass through residues, so when compounded with the significantly increased residues and large noticeable straw which commonly happen in China, the demanding level of anti-blockage of light seeders has been consequently further heightened [2].

Our research team-Conservation Tillage Research Centre (CTRC), Ministry of Agriculture (MOA) first attempted to design light no-till seeder in 1992, with two distinct options: active anti-blockage and passive anti-blockage. Generally, the passive anti-blockage method is used on the field of single-crop a year with relatively small yield and less coverage. By referring to the foreign advanced passive anti-blocking techniques, multi-beams structure and anti-blocking components have been specially developed and strengthened in order to get high trash flow. As a result, more than 10 years efforts have brought out a series of light no-till seeders with passive anti-blocking techniques, possessing advantages of 60% weight lighter, 90% price lower and reasonable anti-blockage ability and thus popularly adopted in single-crop one year regions. While in the double-crop one year fields, due to its strong capability of handling corn stubble, active anti-blocking was chosen. After 16 years research, apart from the strip rotary hoe mini-till seeder and strip chop no-till seeder, we've also achieved with leading technology on wheat no-till seeder through heavy corn residues, which is superior in weight of 50% lighter and expense of 80% cheaper and thereby has formed the series of light no-till seeder in Chinese context.

1. Why to Develop Light No-till Seeder in China?

According to oversea machinery patterns that huge equipment couple with powerful tractors and massive fields, generally in that case blockage is solved by strong cutting forces from heavy weight or lessened by plenty space between openers. Usually, foreign no-till seeders at least weigh about 800-1100 kg/m (Table 1).

Meanwhile, as listed in Table2, light tractor (300-600 kg/m) and small- field in China could only allow middle-sized implements to match with and practice on. So it's impossible for China-produced tractor to lift up such heavy seeder as 800-1100 kg/m even if it is adapted to that tractor's width. The only solution appears to lighten no-till seeder and independently develop small-size no-till seeder with equivalent weight of 300-600 kg/m.

Resulting from 20 years exertion, as illustrated in Table 3, an array of passive and active anti-blocking no-till seeders have been developed, weighing 150-250 kg/m and 300-500 kg/m, respectively, and could be well matched with domestic middle to small-sized tractors.

4th World Congress on Conservation Agriculture — February 4-7, 2009

Table 1. Unit Weight of Foreign No-till Seeders

Country Type/Opener Overall Weight/kg Rows and Spacing/cm Weight per Meter/ kg.m-1

USA Great Plains1500/ Disc 3577 22 19 852

John Deere 750/ Disc 2917 16 19 958

John Deere 1590/ Disc 2917 16 19 959

Canada Morris 7000/ Shovel 11191 52 19 1131

Morris 7300/ Shovel 13409 64 19 1100

Italy GASPARDO/ Disc 4090 22 18 1032

Table 2. Unit Left Force of Domestic middle /Small Tractors

Tractor Type Power/ kw Lifting Force/kg Width/mm Lifting Force per Meter/ kg.m-1

X700 51.5 1570 1930 814

600 44 1071 1798 595

550 40.5 918 1715 535

450 33.1 816 1730 471

350 25.7 734 1634 449

250 18.4 408 1205 338

180 13.24 336 1205 279

Table 3. The Unit Weight of Chinese Light No-till Seeders

Manufactory Type / Opener Overall Rows and Weight per Demanded

Weight / kg Spacing/cm Meter/kg.m-1 Power/kw

Nonghaha, Hebei *2BMFS-5/10 / Shovel 630 10*19 331 44.1

2BMF-6C / Shovel 210 6*20 175 13.2

Xinjiang, Shanxi 2BMF-11 / Shovel 450 11*20 205 44.1

2BMF-2 / Disc 175 2*60 146 11

Wafangdian, Liaoning 2BQM-6 / Disc 900 6*60 250 44.1

Haofeng, Henan *2BMTF-12 / Disc 1200 12*20 500 48

Agro-machinery Station, Liaoning *2BML-2 / Shovel 276 2*60 137 22.3

Nonghaha, Hebei *2BMXP-12 / Shovel 710 12*18 328 44.1

Note: * refers to active anti-blocking no-till seeder

2. Light Passive Anti-blocking No-till Seeders

As mentioned above, because of the relatively small yield and low coverage of residues, passive anti-blocking no-till seeder is applicable to single-crop a year region, but owing to its light weight, stubbles are unlikely to be effectively cut off only by discs, so alternative anti-blocking methods have to be attempted and developed.

2.1 Light Passive Anti-blocking Wheat No-till Seeder

As shown in Fig. 1, light passive anti-blocking wheat no-till seeder normally enhances trash flow by saving an opener with seeder-fertilizer-combined but vertically separated openers, eliminating press-wheels with self-cover opening shovel to enlarge space, and adopting multi-beams structure and front-rear arranged openers to maximize trash flowing clearance and avoid stubbles blockage.

2.2 Light Passive Anti-blocking Corn No-till Seeder

Dual dentate disks and front-mounted removers, which will be described in following text, are yet the two major passive anti-blocking manners in China.

2.2.1 Light Passive Anti-blocking Corn No-till Seeder with Dual Dentate Disks

With the accordance of Fig. 2, the main anti-blocking device of this machine is the disk coulter combined with dual dentate disks. When working, firstly, disk coulter will cut the residue, and then the following dual dentate disks

Figurel. Multi-beams structure and maximized trash Figure 2. Light passive anti-blocking corn no-till seeder

flowing clearance with dual dentate disks

will remove residues from seeding rows, so the narrow-point opener can easily complete no-till seeding. This dual dentate disk method is especially applicable to no-till corn seeding in single-crop one year region.

2.2.2 Light Passive Anti-blocking Corn No-till Seeder with Front-mounted Removers

Those front-mounted and vertical-set removers (see Fig. 3) are capable of correspondingly moving via bearings when encountering with residues or stubbles and self-propelled rotating along with the off-set force coming from the friction between residues and stubbles, in that sense, checking trashes by conducting them to move off removers and thus deviate from opening area.

3. Light Active Anti-blocking No-till Seeder

The main idea of light active anti-blocking wheat no-till seeder is to avoid blockage by cutting straws with actively powered cutting device. Since 2000, China Agricultural University joined with Linfen Agricultural Machinery Bureau, Shanxi Province[3], North-western Agricultural and Forest University[4], Hebei Agricultural University[5] has researched and developed several active anti-blocking no-till seeders, which could not only meet the strict requirement of high yield and also appreciably improve seeding quality.

3.1 Light Active Anti-blocking Wheat No-till Seeder

3.1.1 Strip Rotary Hoe Wheat Mini-til3 6

The strip rotary hoe wheat mini-till seeder mainly use power-driven rotary blades to loose seedbed, cut off stalks and break roots only in the sector of seeding area, so that the openers can pass through easily. As an example cited with Fig. 4, 2BMFS-5/10 strip rotary hoe wheat mini-till seeder, produced by Nonghaha Manufactory, Hebei Province, its main parameters are: rotary width 12 cm, no-till depth 10cm, 2 rows of wheat, 1 row of fertilizer, non-soil-disturbed width 26 cm and disturbance rate 32%. This type of seeder could practice fairly well under different amounts or levels of coverage with 5-10% increase in emergence rate and yield. But its deficiency in productivity and slightly immoderate soil disturbance can form a constraint on its extension progressing.

3.1.2 Strip Chop Wheat No-till78

To reduce soil disturbance and power consumption, a strip chop no-till seeder named 2BMDF-12 strip chop wheat no-till seeder, has been developed. As shown in Fig. 5, the power driven chop blades beside the opener cut off or push away the stalks hanging on the opener and crush the roots. Disk opener, following the tine opener, pushes away chopped stalks or grass to the sides, and then evenly puts seeds into the soil. Moreover, because the driven blades do not touch the ground, reduced soil disturbance and power consumption and increased seed depths uniformity could be achieved. This seeder is proved to have mild soil disturbance rate, even seeding quality and satisfactory emergence rate, and suitable to those areas where economy has been developed or environment is highly respected.

Figure 3. Light passive anti-blocking corn no-till seeder with front-mounted removers

Figure 4. 2BMFS-5/10 strip rotary hoe wheat mini-till seeder

Figure 5. 2BMDF-12 strip chop wheat no-till seeder Figure 6. oblique driven disc wheat no-till

3.1.3 Oblique Driven Disc Wheat No-til91

The key part in this oblique driven disc wheat no-till seeder (Fig.7) is that the disc is not set vertical to the shaft, but at a 5 degree angle. By using disk swaying to push away 80% stalks on the seedbed, the disc only need to cut off the remained 20%. In that way, blockage and energy consumption are considerably decreased. Furthermore, though the vertical disk can only open a 1cm wide furrow, the following oblique opener could extrude this furrow to 45 or 6 cm -wide, hence- let the 4 cm—diameter seed tube pass through.

In order to control the problems of obvious vibration, high resistance force and heavy disk wear, appropriate rotating speeds are selected so as to work properly well under different yield or covering conditions. Indicated by the results tested from the field of Shenze County in Hebei Province which was covered with chopped corn residues, when the stalks on the seedbed were 3.06kg/m2, 0.58kg/m2 before and after planting, 80% stalks were pushed away to the seedbed sides and the roots cut-off rate could reach 98%. In this case, anti-blockage could be significantly achieved.

Advantaged with its simplified light and cheap configuration, this oblique driven disc wheat no-till seeder has promising potential of being widespread extended in China. However, the disc is vulnerably being partially worn over time, so it should be reversible to use the other side if needed. Besides, exceeding amount of fertilizer sometimes tend to cause the consequence of burning seeds.

3.2 Light Active Anti-blocking Corn Rigid-till Seeders

3.2.1 Powered Disc Corn Rigid-till Seeder1101

Powered disc corn rigid-till seeder (Fig. 7) is mainly designed for ridge tillage in northeast China, to actively anti-block via components consisted of serrated disc, driving shaft and depth-control wheels. Specifically, the serrated disc is firmly fixed with driving shaft and rotating correspondingly with it, vertically to the ground and

Figure 7. Powered disc corn rigid-till seeder Figure 8. Powered coulter corn rigid-till seeder

paralleled with heading direction. At the same time, by bearings depth-control wheels are semi-connected with driving shaft and are able to every possible spatial rotation. During operation, serrated disc, driven by tractor, cuts corn roots and residues, and open furrows, and then the following narrow-point opener can further open the furrows and produce a comfortable seedbed for the seeds without the occurrence of residue blocking.

Commonly, depth-control wheels travel on the rigids, and, with the help of ground resistance, they could rotate accordingly and uniformly guarantee the cutting strength of serrated discs and seeding depth of openers. In addition, the uneven suburbs of depth-control wheels could interact with rigid side-face and help to prevent machinery from slipping into rigid furrows.

3.2.2 Powered Coulter Corn Rigid-till Seeder1111

With the objective of merely cutting soil not turning over soil in the consideration of preserving soil sustainability, a powered coulter corn rigid-till seeder has been developed by mutual efforts of China Agricultural University and Fuxin Agricultural Machinery Bureau, Liaoning Province. As presented in Fig. 8, driving power is originally output from tractor to gearing box, and then transferred to roller chain which finally propels the rotating coulter that is set right on the front of opener. Opener and coulter are supposed to be so closely installed that rotating coulter is possible to swing away disturbing stalks and clear blockage as long as they are stocked on the opener handle. Under the help of this front-mounted and powered coulter which could pre-open a 5-6 cm wide furrow before the arrival of seeding openers, the real opening conditions are significantly improved, thereby press-wheel slippage and seeding depth variability could also be reduced.

3.2.3 Cutting and Digging Corn No-till Seeder1121

Briefly, the principles of cutting and digging corn no-till seeder (Fig. 9) are to motivate cutting and digging devices which are fixed on the front of opener. Because these devices only need to cut corn root and dig it out individually with no chopping, lower rotating rates demand less energy and thus conserve more. The cutting device previously slices the bed and breaks corn roots beneath it, and then keeping acting to the curved surface, digging device will follow the crack to unearth the roots so that the seeds could be comfortably planted in soft bed soils. Additionally, stalk eliminating, seeding and fertilizing are designed to be completed over a single bout.

4. Experimental Tests Results and Discussions of Wheat No-till Seeders

During the years from 2004 to 2006, comparative experimental tests of 2BMDF-12 strip chop wheat no-till seeder; 2BMFS-5/10 strip rotary hoe wheat mini-till seeder and John Deere-1590 disc no-till seeder were carried out in Daxing District, Beijing, with outcomes elaborated as follows[13]:

1. Trash flow: 2BMDF-12 strip chop wheat no-till seeder and 2BMFS-5/10 strip rotary hoe wheat mini-till seeder performed less pleasantly than John Deere-1590 disc no-till seeder in terms of soil disturbance rate and residue retaining rate. However, in the double-crop a year region which is featured with massive residues and where wheat seedless are usually able to shortly catch up, foregoing slight unsatisfactory performance could hardly affect the process of soil and water conservation.

Figure 9. Cutting and digging corn no-till seeder

2. Seedbed and emergence: 2BMDF-12 strip chop wheat no-till seeder and 2BMFS-5/10 strip rotary hoe wheat mini-till seeder demonstrated encouragingly performance relative to John Deere-1590 disc no-till seeder, with higher emergence rate of 9% and 6%, respectively, heavier wheatears of 2% and 6%, and greater output of 3% and 5% as well. It's reasonable to attribute these satisfactory outcomes to the less coverage of seedbed and promising emergence rate in the treatment of active anti-blocking devices which will develop a soft and favorable under-earth environment for crop roots.

3. Fuel consumption: on the aspect of fuel consumption, 2BMDF-12 strip chop wheat no-till seeder and 2BMFS-5/10 strip rotary hoe wheat mini-till seeder individually demand 15% and 35% more than John Deere-1590 disc no-till seeder, resulting in 10 yuanha-1 and 15 yuan 10 yuanha-1 extra fuel cost to the later treatment. But considering the 160 yuanha-1 and 180 yuanha-1 less depreciation and 180 yuanha-1and 300 yuanha-1higher income, light active anti-blocking no-till seeders contributed more financial benefits than John Deere-1590 disc no-till seeder, though on the respect of resource and environment, their advantages tended to the opposite direction. Therefore, economically, non-soil-disturbance anti-blocking device or oblique driven disc appeared to be the leading pattern in the future.

5. Experimental tests results and discussions of corn rigid-till seeders

Different treatments of powered disc corn rigid-till seeder and BAFFOLA corn rigid-till seeder were layout in Sujiatun District of Liaoning Province, producing results as below:

1. Trash flow: as to trash flow ability, powered disc corn rigid-till seeder performed better than BAFFOLA corn rigid-till seeder, but with regard to soil disturbance rate and residues retaining rate, the two treatments displayed no significant differences.

2. Fuel consumption: powered disc corn rigid-till seeder consumed 1.5% less fuel than BAFFOLA corn rigid-till seeder, which could be possibly caused from the evidently distinguishing weights.

3. Seedbed and emergence: powered disc corn rigid-till seeder represented roughly similar emergence rate with BAFFOLA corn rigid-till seeder, albeit producing 4.5% more grain. Less soil disturbance could be a likely causal factor to the effects of rigid-form maintaining and soil water reservation.

6. Conclusion

Rather than following the steps of foreign heavy-sized no-till seeders, China has developed a series of light no-till seeders in its own domestic context and they have been proved, based on a great many practices, to be of vital importance in widespread extension. Regarding to the key technique of anti-blocking, let passive anti-blocking device thoroughly exert their advantages in middle or low productivity regions; while when coming up with the confliction between light weight and pressing demand of anti-blocking ability in high producing area, active antiblocking technique has been creatively explored. In that, two levels of no-till seeders which are respectively light series of 100-250 kg/m weight, middle or small tractor powered and 2000-7000 yuan/m cost and the other series of

316-500 kg/m, large tractor and 4000-10000 yuan/m, cope with two levels of grain producing capabilities. Thanks to the proper anti-blocking solutions, seeding qualities, crop yield and operation input all have been improved, which will also be much helpful to widen popularity no-till seeders and facilitate their extension progress. Till 2007, throughout the whole country there have been over 80 thousand sets of no-till seeders and 2 million more hector area setting out to apply conservation tillage, among which active anti-blocking no-till seeders were more than 20 sets and the area of double-crop a year and conservation tillage a whole year occupied more than 600 thousand hector. China is the first country in the world who leads her conservation tillage extension progress onto all-round stage with light implements.

References

1. Gao Huanwen, Li Wenying, Li Hongwen. Conservation tillage technology with Chinese characteristics [J]. Transactions of the Chinese Society of Agricultural Engineering, 2003,19(3),1-4;

2. Zhou Xingxiang, Gao Huanwen, Li Xiaofeng. Experimental Study on Conservation Tillage System in Areas of Two Crops a Year in North China Plain[J]. Transanctions of the Chinese Society of Agricultural Engineering, 2001,17(6),81-84;

3. Chai Yuejin. Test and Research on Cingulum Zero Tillage Covering Seeding-machine[J]. Chinese Agriculture Mechanization, 2004,(2),39-40;

4. Xue Huilan; Xue Shaoping; Yang Qing; Yao Wansheng; Lei Shuwu Implementation of combined work of straw crushed for mulching and seeding with fertilizer and design of the machine[J]. Transactions of The Chinese Society of Agricultural Engineering, 2003,19(3),104-107;

5. Zheng Dong xu, Jiang Hai yong, Li Bing, Li Hong wen, Zhang Jin guo. Study on the no-tillage mulch planter for wheat under the bestrow of the whole mealie straw[J]. Journal of Agricultural University of Hebei, 2003,S1,285-287;

6. Jiang Jinlin,Gao Huanwen. Corn rootstalk and residue cutting mechanism of no-tillage planter[J]. Transactions of The Chinese Society of Agricultural Engineering, 2004,20(2),129-131;

7. Wu Ziyue, Gao Huanwen, Zhang Jinguo. Study on Cutting Velocity and Power Requirement in a Maize Stalk Chopping Process[J]. Transactions of The Chinese Society of Agricultural Machinery2001,32(2),38-41;

8. Yao Zonglu, Li Hongwen, Gao Huanwen, Wang Xiaoyan, Zhang Xuemin. Experiment on No-till Wheat Planter under the Bestrow of the Maize Stubble in Double Cropping Area [J]. Transactions of the Chinese Society for Agricultural Machinery, 2007(8),57-61;

9. Ma Hongliang, Gao Huanwen, Li Hongwen, Wei Shuyan. Design and Experiment of No-till Planter with Oblique Driven Disc[J]. Transactions of the Chinese Society for Agricultural Machinery, 2006,37(5) ,45-47;

10. Wang Qingjie, He Jin, Yao Zonglu, Li Hongwen, Li Wenying, Zhang Xuemin. Design and Experiment on Powered Disc No-tillage Planter for Ridge-tillage[J]. Transactions of the Chinese Society for Agricultural Machinery, 2008,39(6) ,68-72;

11. Xu Dijuan, Li Wenying, Wang Qingjie. Development of 2BML-2(Z) type no-till maize seeder in ridge-field [J.] Journal of China Agricultural University, 2006, 11 (3),75 -78;

12. Jiang Jinlin, Gao Huanwen. Corn rootstalk and residue cutting mechanism of no-tillage planter [J]. Transactions of The Chinese Society of Agricultural Engineering, 2004.20(2),129-131.

13. Wei Yanfu, Gao Huanwen, Li Hongwen. Experiment and analyses of the adaptabilities of three wheat no-tillage drills on corn stubble in the areas with two ripe crops a year [J]. Transactions of The Chinese Society of Agricultural Engineering, 2005, 21(1), 97-101.

Avoiding Soil Compaction in CA: Controlled Traffic Systems for Mechanized CA and their Effect on Green House Gas Balances

J.N. Tullberg and CTF Solutions

Brisbane, Australia (Email: jeff@ctfsolutions.com.au)

Wheel and tyre combinations used on cropping land cannot function without compacting soil to increase its strength. If we spread this impact randomly over fields it is highly visible, damaging, and an ongoing incentive to tillage. Alternatively, we can use controlled traffic and confine damage to permanent traffic lanes, where it will improve trafficability and traction. This requires accurate guidance, and compatible machine track, tyre and operating widths.

Guidance can be provided at low cost by furrows in more intensive Permanent Raised Bed (PRB), or at moderate cost by RTK-GPS in more extensive Controlled Traffic Farming (CTF). Research on both systems has demonstrated major productivity/sustainability benefits, and farmer adoption has shown that these occur on-farm, in practice. Research and adoption of CTF occurred primarily in extensive farming in Australia, in contrast to PRB which was focused largely on more intensive environments, often in low-resource areas.

PRB and CTF are really variants of the same fundamental CA ideas. With controlled traffic:

• Energy requirements of field operations are reduced by ~ 50%.

• Greater infiltration and plant available water capacity increase water use efficiency.

• Hard, compacted permanent wheel lanes improve the timeliness of all operations.

• Material and time input per unit production is reduced.

• Crop yields are greater and cropping frequency increases in some environments.

• Soil erosion and waterway pollution is reduced.

• Soil carbon and greenhouse gas balances can be significantly improved.

The paper will provide evidence of each of these, with greater detail on greenhouse gas impacts, particularly fossil energy use (tractor fuel and equipment manufacture; herbicide and fertiliser manufacture) and soil emissions (soil structure/hydrology impacts on nitrous oxide and methane production, soil organic matter).

The paper will demonstrate that significant improvements are relatively easy to achieve when traffic is controlled, but a number of cropping system changes are crucial to this process. Overwhelmingly, the measures required to improve environmental outcomes are identical to those required for improved productivity and economics. Anecdotal data suggests a positive social impact.

The underlying idea of Conservation Agriculture is care for the soil resource. Controlling traffic is a fundamental part of this care for all soils known to the author

For most practical purposes, mechanised agriculture depends on wheels — usually pneumatic tyred. Wheels supporting relatively small loads (<1t) cause significant structural damage and compromise productivity and sustainability in most of soil types. Controlling traffic, whether by the use of permanent raised beds or "on the flat" avoids this damage and provides a range of benefits, direct and indirect.

To date, the major focus of conservation agriculture research and extension has been on the reducing or eliminating tillage. In Australia this has often involved the replacement of tillage with herbicide weed control, with other system changes occurring only slowly. More recently many farmers have found that zero tillage works much better with controlled traffic, and controlled traffic farming provides more options for system change by improving timeliness and increasing water use efficiency.

This paper attempts to provide a concise comparison and evaluation of the impact of these systems on greenhouse gas emissions from cropping. The objective is to compare systems with and without soil disturbance, and systems with and without compaction and disturbance. Real systems are considered here where, (for instance) "zero tillage" is compromised by occasional requirements to till out harvester ruts, and "zero compaction" is compromised by the need to maintain 10 — 20% of field area as permanent traffic lanes.

Data given here is relevant to three typical systems (defined below) used in extensive semi-arid dryland grain production in Australia, with appropriate equipment and herbicide data. Despite the large differences in scale and level of technology, much of this approach would apply equally well to dryland grain production in northern China. Permanent raised beds (PRB) are a very different situation, but most of the same ideas apply. The systems are:

Stubble mulching, where traditional tillage has been reduced to 1-3 minimum-inversion tine or sweep operations, with 1-3 herbicide operations. Soil is tilled and wheeled, with some residue retained. (probably most common system in Australia).

Zero tillage, with no regular soil disturbance except at planting and full herbicide weed control. Occasional chisel tillage or subsoiling is required to relieve soil compaction, or deal with surface ruts after wet harvests. Soil is wheeled but not tilled, most residue retained. (probably less common than stubble mulching).

Controlled traffic farming, (CTF or PRB) with all heavy wheels restricted to permanent lanes and oriented to provide drainage and safe disposal of surface water. CTF overcomes the problems of wheel traffic in the cropping area, but requires accurate guidance and equipment systems with compatible working, track and tyre widths. No tillage, maximum residue, but 10-20% area is wheeled (this is the least common practice, but growing rapidly in Australia).

The relative impact of stubble mulch (tilled wheeled), zero tillage wheeled and CTF (non-tilled non-wheeled) on infiltration rates, plant available water capacity and earthworm numbers in a clay vertosol is illustrated in figure 1, a), b), and c). Figure 1 d) illustrates the effect of controlling traffic on the tractor power required for planting, where the lower section of the bars illustrates the draft effect of disturbing soil compacted by random traffic (v. non-compacted soil), and the upper section the tractive efficiency improvement when operating on permanent traffic lanes. The centre bar (tractor only) represents the situation where the grain harvester is not included in the controlled traffic system.

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This data — discussed in more detail in Tullberg et al. (2007) — explains why greater water use efficiency, and greater crop yields can be achieved in controlled traffic zero tillage systems (CTF or PRB), while simultaneously reducing fuel and tractor power requirements. For most practical purposes, CTF systems don't waste power compacting soil under tractor tyres, and also avoid the additional power wasted by non-CTF systems in re-loosening soil, (achieving only partial soil amelioration over a limited depth range)

Grain yields from these long-term, side-by-side plot trials precisely reflected the increase in water available to the crop. In side-by-side comparisons, all treatments have to operate at the timescale of the slowest treatment (i.e. stubble mulch), so on-farm yield improvements have been much greater than the 15% effect demonstrated in these

Environmental Effects — Soil, Water

The beneficial environmental effects of CTF or PRB are well accepted and have been quantified in a number of environments (e.g. Wang et al. 2008). Greater infiltration and plant available water capacity reduces runoff and erosion while supporting greater cropping frequency. Reduced runoff obviously reduces soil erosion and waterway pollution by soil, fertiliser and agricultural chemicals. Reduced tractor power requirement and fuel use is also a significant environmental benefit.

The system impact of CTF can be extremely important. Harvesting grain crops high, so minimal residue can be well spread, with no harvester traffic to obstruct re-planting, has allowed cropping frequency to increase. With precision (2 cm) autosteer it is also not difficult to plant interrow. This has allowed unsophisticated planters to operate effectively in heavy residue, placing seeds in a precise relationship with the previous crop, avoiding disturbance of the standing stubble and achieving additional disease control benefits.

Timeliness and damage-free access to growing crops (with system layout for proper drainage) is the other major system impact, allowing efficient in-crop application of fertiliser or agricultural chemicals. CTF has allowed some Australian farmers to claim "doubled production with reduced costs", including fertiliser and herbicide costs (e.g. Ruwolt 2008). These claims have not been examined in detail, but a large-scale survey of CTF farmers has demonstrated an average ~70% improvement in gross margin, with farmers attributing the effect equally to improved soil conditions and CTF system effects.

As with all forms of conservation agriculture, uptake of CTF has been relatively slow. No precise information is available but it has been estimated that less than 5% of Australian farmers are using full CTF (all heavy wheels on permanent traffic lanes). Another 20% are probably in some partial controlled traffic system, and another 30% might be in zero tillage.,

Environmental Effects — Greenhouse Gases

A simple Excel spreadsheet approach has been used to compare greenhouse gas (GHG) emissions from the different farming systems, and a copy of this spreadsheet appears here as Figure 2 — a numbered series of tables. The tables follow a rational order, dealing first with those emissions that are easily quantified and converted to CO2 equivalent.

Input-Related Emissions

Fuel emissions obviously relate to the operations involved in the cropping system, and the energy requirement of these operations. Operations typical of the each system are set out in Table 1, where zero tillage has been assumed to need one tillage operation every three years, and CTF requires less spraying, but additional in-crop liquid N application. Fuel requirements are given in Table 2, (based on DPIF 2008 and Tullberg 2000). The total field fuel requirement for each system appear in the right-hand columns of Table 2.

Herbicides emissions, related to the energy embodied the materials, manufacture and transport etc., are large. Zentner (2004) has tabulated the energy data quoted for commonly used herbicide in Table 3. This table also includes an estimate of the frequency with which each herbicide is used, to allow calculation of a "mean spray impact" — the CO2 equivalent of the average herbicide spray operation, set out below Table 3.

Fertiliser nitrogen is usually represents the largest single energy input to cropping. Nitrogen efficiency of cereal production is generally very poor, with a mean value often around 40%. Fertiliser application typically occurs at seeding, and large nitrogen losses are associated with subsequent rainfall events. Loss mechanisms include leaching and denitrification associated with high water-filled porosity, which occurs in situations of soil compaction and waterlogging. These occur more often in zero tillage when seed and fertiliser are placed in narrow slots cut into a compact surface soil where random traffic has reduced infiltration, exacerbating the problem, particularly in some soils (Rochette 2008).

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Fertiliser is applied only to the highly-porosity crop bed areas of CTF where greater soil organic matter and biological activity will tend to reduce losses, and migration into permanent wheel lanes will be restricted by their limited porosity. Leaching could occur more rapidly from beds with better infiltration, but CTF facilitates efficient in-crop fertiliser application, using liquid N via sprayers to achieve high workrates. This is the basis of the different N fertiliser requirements quoted in Table 4, which includes the energy embodied in fertilisers (Zentner 2004), and the reduction in CO2 output which occurs because most fertiliser is produced from natural gas.

Soil Emissions

Nitrous oxide (N2O) has approximately 310 times the greenhouse impact of carbon dioxide, so small quantities have a significant global warming effect when expressed in terms of their carbon dioxide equivalent, "CO2 -e". Many authors have demonstrated the association of emissions with compaction, porosity and pore connectivity (e.g. Ball et al.2008).

Methane (CH4) has approximately 23 times the greenhouse impact of carbon dioxide, but emissions from dryland cropping are small compared with those from animal production or paddy rice production. Nitrous oxide and methane emissions are often studied together, and a number of authors have compared emissions from wheeled and non-wheeled rows and interrows of potatoes (e.g Ruser et al.1998), but this has usually been carried out in an environment of intensive tillage and random traffic.

Research into CTF impacts on greenhouse gas emissions is rare, but Vermeulen and Mosquera (2007) compared nitrous oxide and methane emissions from random traffic and "seasonal" precision CTF and these results are the basis for the values summarised in Table 5a. They demonstrate a large, consistent and significant reduction in nitrous oxide emissions from seasonal CTF, and a small improvement in the methane balance, over several crops.

It is highly speculative to use results obtained in European organic production to quantify greenhouse gas impacts on semi-arid production in Australia or China, but no other data is available, and porosity and pore continuity data is consistent with the emissions from random traffic zero tillage (v. conventional tillage), demonstrated by Aulakh et al. (1984). Porosity of zero till is likely to be less than that of stubble mulch, increasing emissions, so zero till emissions are assumed to be greater than those from stubble mulch by an increment similar to that between controlled and random traffic. Values are set out in Table 5b. Duration time estimates for emissions and total nitrous oxide and methane estimates for each system are set out in Table 6, together with the CO2 e values.

Overall totals are given in Table 7, in which emissions related to inputs, based on good evidence, are separated from the more speculative soil emission estimates.

Conclusions

1. Greenhouse gas emissions from inputs (fuel, herbicides and fertiliser) are demonstrably smaller from controlled traffic zero till systems, compared with (random traffic) zero tillage or stubble mulch systems.

2. Evidence on greenhouse gas emissions from soils indicates that these should also be substantially smaller from controlled traffic systems. Surprisingly, emissions from (random traffic) zero till appear greater than those from stubble mulch tillage.

3. Further work is required to establish more precise values for nitrous oxide and methane emissions under different cropping systems.

Controlled traffic or permanent raised bed farming is based on a self-evident truism "plants grow better in soft soil, wheels work better on roads". It has been shown to increase productivity, reduce costs and improve all measures of environmental impact. Different assumptions might change the quantum of the improvement due to CTF, but or evidence suggests it will still be very large.

CTF requires more precise field guidance, and compatible machine track, tyre and operating widths. Greater standardisation would make adoption much easier in all environments.

References

Aulakh M. S. Rennie D. A. and Paul E. A. (1984) Gaseous Nitrogen Losses from Soils Under Zero-Till Compared with Conventional-Till Management. J Environ Qual 13:130-136

Ball B.C., Crichton I. and Horgan G.W. (2008). Dynamics of upward and downward N2O and CO2 fluxes in ploughed or no-tilled soils in relation to water-filled pore space, compaction and crop presence. Soil and Tillage Research. (in press)

DPIF (2008) Selection and matching of tractors and implements. http://www2.dpi.qld.gov.au/thematiclists/9155.html

McHugh, A.D. Li Hongwen, Zhang Liqin, E Shengzhe, Ma Zhongming, and Cao Xinhui (2006) Controlled traffic farming takes Conservation Agriculture into China. In Proceedings of China-Canada Conservation Agriculture Forum. September 21-23 Beijing, China. Pp: 75.

Rochette P ( 2008) No-till only increases N2O emissions in poorly-aerated soils. Soil & Tillage Research 101 (2008) 97-100

Ruser,R, . Flessa,H., Schilling,R., Steindtl,H., Beese F. (1998). Soil compaction and fertilisation effects on nitrous oxide and methane fluxes in potato fields. Soil Sci. Soc.Am..J. 62; 1587-1595

Ruwolt, R. (2008). CTF/No till Farming 2008 — What We Learned? 6th Australian controlled traffic conference, Dubbo NSW. Proceedings, p.50.

Tullberg J.N. (2000) Traffic Effects on Tillage Energy. Journal of Agricultural Engineering Research 75(4).375-382.

Tullberg J.N., Yule D.F. and McGarry D. (2007) Controlled traffic farming— From research to adoption in Australia. Soil & Tillage Research 97 272-281

Vermeulen, G.D., Mosquera, J. (2008). Soil, crop and emission responses to seasonal-controlled traffic in organic vegetable farming on loam soil. In press, Soil Tillage Res., doi:10.1016/j.still.2008.08.008

Wang Xiaoyan, Gao Huanwen, Tullberg J N , Li Hongwen, Kuhn Nikolaus, McHugh A. D. and Li Yuxia(2008) Traffic and tillage effects on runoff and soil loss on the Loess Plateau of northern China. Australian Journal of Soil Research, 46, 1-9

Zentner,R.P., Lafond, G.P.,Derksen, D.A.,Nagy,C.N., Wall,D.D., May, W.E. (2004) Effects of Tillage Method and Crop Rotation on Non-Renewable Energy Use Efficiency in the Canadian Prairies. Soil and Tillage Research 77; 125 - 136.

Improving No-Till Seeding Quality with Low Disturbance Furrow Openers and Residue Handling Devices

Augusto Guilherme de Araújo

Agronomic Institute of Parana State (IAPAR), C.P. 481, CEP 86001970, Londrina, Paraná, Brazil

(Email: agaraujo@iapar.br)

In the last two decades, no-tillage in Brazil has increased rapidly reaching more than 25 Mha in 2006. This widespread adoption of no-tillage for crop production, specially corn and soybeans, has generated new mechanization challenges, such as: seeding with high amount of residues over the soil surface; assure high seeding quality specially regarding emergence speed and furrow cover with residues and, finally, decreases the energy demand during seeding operation. This presentation will focus the results obtained by a modified type of a narrow chisel opener for fertilizer deposition, in order to reduce the demand of energy during seeding operation, and also the effects of residue handling components designed for covering seed furrow under high amount of residues (more than 8 Mg ha-1).

The chisel opener is commonly used in Brazilian no-till seeders as a soil-engaging component for fertilizer deposition due to its capacity to penetrate in hard and, specially, medium to clay soils which, in general, present a surface compaction after some years of no-till adoption. There are many different designs and types of commercial chisels in the market and consequently the performance regarding energy demand and soil mobilization are variable. The depth of operation (H) for this component should not be more than 100 mm because energy demand and soil mobilization increase with depth.

The objective was to develop a new design for the chisel opener in order to reduce energy and soil mobilization for the most common operational conditions adopted by farmers. Sixty designs were evaluated and the best results were obtained for a chisel's rake angle of 20°, pointer thickness of 20 mm and frame thickness of 13 mm. During operation, the chisel compresses the soil forward and upward breaking it in a transversal direction. The selected design required less energy to break the soil and its mobilization was smaller. Results showing the relationships between design parameters of the chisel, named rake angle, pointer thickness and H/L (relation between operation depth and the distance from a vertical projection and the frame, which defines the parabolic shape of the chisel) and horizontal draft force, vertical force and soil mobilization area are discussed.

Residue handling components for no-till seeders, like row cleaners, have been used in temperate regions to remove the residues ahead of the openers as a way to clean the soil surface and raise soil temperature for the seeds. In Brazil, they have been evaluated as an alternative to avoid residue's clogging in the openers, mainly in the chisel. Meanwhile, when residue handling components operate afterwards of the openers, they can return the residues over the seed furrow protecting the soil surface from direct exposition to solar radiation and from the impact of rains and preventing from excessive soil temperature and loss of soil moisture in the seeding region, which are very important aspects to achieve a high seeding quality in tropical and dry regions.

Different types of residue handling components, both ahead and afterwards of the chisel opener, are being evaluated comparing with traditional soil-engaging components of no-till seeders under high amount of residues and distinct seeding periods. The effect of these components over soil covering, soil temperature and moisture in the seeding zone and also in the speed of emergence for corn seeds are discussed.

Resource Saving Equipment for Conservation Agriculture Leading to

Higher Productivity and Profitability

Nawab Ali

Indian Council of Agricultual Research, Krishi Anusandhan Bhawan II, Pusa, New Delhi, 110 012, India

Agriculture is a complex and risk-prone profession but it is a must for the survival of human being on the planet earth. Resource conservation in agriculture through minimum tillage, in-situ management of crop residues, saving in water use and that of inputs like seeds, fertilizers and pesticides are needed for higher productivity and profitability on sustainable basis. This could be achieved through appropriate engineering interventions which have shown an increase of 10-35% in productivity, 20% saving of seeds, 15-20% saving in fertilizer, 15-25% enhancement in cropping intensity and 30-50% increase in farmer's gross income and return and thereby resulting in better quality living of farmers.

The goal in production agriculture is to get the higher productivity out of the limited land and water resources on sustainable basis whereas the goal in post-production agriculture is to prevent post-harvest losses and produce value added products. All these are being done through a set of agricultural operations carried out by farmers to produce biomass of plant and animal origin to meet the food and feed requirements of people and their livestock.

For each operation, appropriate tools and machines are required to achieve timeliness in operation, enhanced inputs use efficiency, operator's comfort, higher productivity, lower cost of cultivation and better quality products. Tillage is a laborious and time consuming operation and uses maximum energy in crop cultivation.

Tools and Machines

Mechanization plays a very important role in enhancing the agricultural production and productivity specially that of dryland areas leading to better profitability. Appropriate tools and equipment improve work efficiency of doing work at low cost, faster speed, with high precision and more comfort. Farm mechanization is a process of adoption of need based, location specific, efficient and precision tools, devices, equipment and machines matching to available power source, suitable for local soil, crop and socio-economic conditions. It helps to lower the operation cost, improve resource use efficiency, timely operation, enhance crop productivity and profitability. Dryland agriculture requires a tillage practice which can conserve basic resources namely soil, water and nutrients. Both, prevention of soil erosion and in situ moisture conservation are of utmost importance. Tillage practices also aim at complementing basic soil and water conservation measures such as graded bunds, land leveling and/or smoothening of surface. Rapidity of tillage operations for keeping the field ready for seeding immediately after the rain sets in is the key to the success of crops. It gains further importance when a second crop is to be sown subsequent to the harvest of first crop. Mechanization of agriculture has been shown to result in :

• Higher productivity to the extent of 10-35%.

• Saving in seeds and fertilizers (15-20%)

• Enhancement of cropping intensity (15-25%).

• Increase in gross income and return to the farmers (30-50%).

• Dignity to agriculture profession and better living conditions

Resource Conservation Measures

Resource conservation agriculture generally implies to the systems of cultivation with minimum tillage, in-situ management of crop residues; savings in water use and that of inputs like seeds, fertilizers and pesticides. Minimum tillage is aimed at reducing the soil manipulation activities to a bare minimum that is necessary to facilitate favourable seedbed condition for satisfactory germination, plant establishment and crop growth. Excessive tillage can be minimized either by eliminating the operations which are not cost-effective or combining the tillage, seeding and fertilizer application in one pass operation. Zero tillage is however an extreme form of minimum tillage. Experiments

have shown that minimum tillage has improved soil conditions due to decomposition of plant residues in-situ, facilitated higher infiltration due to vegetative matter present on the top soil and passage formed by the decomposition of old roots, less compaction to soil by the reduced movement of tractor and heavy tillage equipment and less erosion compared to the conventional tillage. These advantages are more visible in coarse and medium textured soils. Use of appropriate equipment and power source would save a considerable amount of energy and time and thereby reduction in cost of cultivation.

Energy and Cost Effective Equipment

Energy is a basic requirement for the development of every sector of Indian economy including that of agriculture and allied sector. As a result, consumption of energy in all forms has been steadily rising all over the country. Rising prices of oil and gas and potential shortage in future lead to concerns about the security of energy supply needed to sustain our economic growth.

Increased use of fossil fuel also caused environmental problems both locally and globally. As a result, promotion of energy conservation and increased use of renewable energy sources are the major two options to have a sustainable energy supply. Besides, increase in energy and water productivity need immediate attention. A good number of solar gadgets; such as solar dryer, solar water heater, solar cooker, solar refrigerator, biogas plants, biomass cook stove, biomass digesters, wind powered generator, alternate fuels for running engines have been developed and need to be promoted on a large scale.

Direct drilling equipment such as no-till drill, strip-till drill and roto-till drill for wheat after rice were compared with conventional tillage sowing as practiced by farmers. The result showed that no-tillage drilling was the most time, energy and cost effective for 70%, 67% and 6% respectively over the conventional practice. Raised bed planting has shown saving of 55%, 42%, and 44% in time, energy and cost of operation over conventional system on fresh beds. On permanent beds, these are 63%, 56% & 57% respectively,

New science-based farmer participatory consortium model for efficient management of natural resources and for improving livelihood of poor rural households has been developed and tested and found substantial reduction in run-off and soil loss, improvement in ground water level, reduction in pesticide use, better land cover and overall enhancement in productivity and farmer's income. The major driving forces for the success are selection and construction of watershed and check dam on a demand driven basis, higher farmers participation in watershed programme, good local leadership, use of improved agricultural tools and implements that provide benefits to large segment of the farming community.

As of now, technically feasible, economically viable and socially acceptable water resource conservation technology and equipment are pressurized irrigation systems. Drip and micro need to be popularized for row crops, horticulture and widely spaced high value cash crops on undulating terrains, shallow and porous soils and in water scarce areas.

Besides tillage and water conservation tools and machines, there are equipment which help to conserve and save inputs like costly seeds, fertilizers and timely harvest the crop to save from weather and pests. Some such equipment and machines are plastic mulch laying machine, inclined plate planter, self propelled rice and vegetable transplanters, power weeders, high capacity multicrop threshers and grain combines.

Water and its Nutritional Productivity

Water is one of the crucial limiting factors for increased food and fibre production to meet the demand of an ever growing population under increasing competition with other uses of water (municipal, industrial, environmental etc.). The optimum population of the planet earth depends to a large extent on the availability of water for both rainfed and irrigated agriculture to grow crops and produce food, in the most efficient way. Here comes the importance of water productivity in terms of nutrients rather than biological mass per unit of land and water. The nutritional productivity of water is calculated in terms of protein, energy, minerals and vitamins output per unit of water.

The concept of water productivity has, in recent year shifted from crop per unit area to crop per unit volume of water. Water productivity has been expressed in kg/m3 whereas nutritional water productivity (NWP) is expressed in nutritional units/m3 (Protein, energy, mineral, etc.).

In estimating NWP, one source of uncertainty is the ratio of yield per unit of water consumed. Another source of uncertainty is the nutrition content of the product in which there are significant deviations. For example, the energy content of cereals varies from 2700 kcal/kg to 3500 kcal/kg. Water productivity in kg/m3 or water requirement in m3/kg for some of the food commodities have been worked out.

Future Strategies

Foodgrain production of Indian in 2007-08, was about 230 million tonnes. In order to enhance Indian foodgrain production to a higher level, an integrated approach focusing on land preparation, inputs use efficiency and farm management using appropriate mechanization is needed. As of now, it is possible to double foodgrain production in India by the end of the 11th Plan (2007-2012) with available technologies. Some of the immediate needs are package of commodity and location specific production technology and equipment; right and quality inputs of seeds, fertilizers, pesticides and water; marketing of produces; and facilities for processing and value addition in rural sector to provide better economic returns to the farmers and rural entrepreneurs. This requires investment in post-harvest facilities like cleaning and grading, cold storage and marketing, processing and value addition and wholesale and retailing of the processed products. This would also lead in arresting unhealthy urbanization and result in India becoming a large foodgrain producers for the world. Comprehensive farm management and a missionary zeal through leadership at the highest level would help to achieve the target of food and nutritional security for the people of the country.

Session 1.6: Genetic Strategies

Constraints to Zero Tillage in Mediterranean Environments

E. Acevedo*, E. Martínez and P.Silva

Laboratorio de Relación Suelo-Agua-Planta. Facultad de Ciencias Agronómicas. Universidad de Chile.

Casilla 1004. Santiago. Chile *Corresponding author. E-mail address: eacevedo@uchile.cl

The projected world food demand will require a sustainable intensification of field crops agriculture, fine tuning genotypes and agronomy for the various growing environments. No-till is central to agricultural sustainability, yet its adoption in Mediterranean environments is lagging behind, particularly in high yielding areas. These environments are characterized by having winter rainfall and hot, dry summers such that crop residue decomposition on top of the soil does not start until the break of autumn rains and decomposition occurs at low temperatures. The accumulated residues cause problems to the planters; allelochemicals limit germination and cause seedling mortality and sexual reproduction of pathogens occurs on the residue during the summer. When rainfall is high slugs thrive in the cool, humid environment provided by the straw. Eventually farmers burn the residues defeating a major purpose of conservation agriculture. Based on our experience with no-till in Central Chile, a high yielding Mediterranean environment, we briefly analyze the effects of crop residues on the soil, the effect of crop residues on the next crop of the rotation and propose agricultural practices and ideotypic traits of wheat for no-till that would help to overcome most of the production problems in these environments. The proposed traits are intended to overcome changes that occur in soil mechanical impedance, anoxia, weed control, diseases and allelopathy when no-till practices are adopted.

Key words: No-till, cereal crops, sustainable agriculture.

Globally the wheat demand is expected to increase to one billion Mg by the year 2020, what implies a fantastic intensification of the production systems to almost double the mean wheat yield, from 2.5 to 4 Mg ha-1 (Rajaram, 2001). The intensification has to be done in a sustainable way and it will require an almost perfect coupling of genotypes, agronomy and crop management (GM) to increase system productivity avoiding damage to the environment. In this paper we focus on the agronomical and breeding implications of using no-till, a central management component of any agricultural sustainable system, for Mediterranean environments. We tap heavily on our 14 year experience working with no-till in the Mediterranean environments of Central Chile. Based on a parallel between no-till (NT) and conventional tillage (CT) systems we disclose phenotypic traits of interest for high yielding Mediterranean environments.

The Mediterranean Environments

The mediterranean eco-region includes all the areas with a prevalent mediterranean climate. It includes the countries around the Mediterranean Sea, California in the US, Central Chile, South-West Australia and the Cabo region in South Africa (Boydak and Do6ru, 1997; UNESCO-FAO, 1962; Di Castri, 1973). The Mediterranean climate is characterized by cool rainy winters; hot, dry summers with high solar radiation and high water evaporation and a moderate influence of marine air throughout the year (Figure 1) (Leisz, 1982). It corresponds to Koppen's (1923) olive climate, due to the cropping of olives in this environment.

The Mediterranean environments, particularly those in the Mediterranean Sea, are mostly affected by intensive tillage, overgrazing and the use of fire (Boydak and Doóru, 1997; Naveh and Dan, 1973). Conservation agriculture is aimed at counteracting the negative effects of conventional agriculture on the renewable natural resources. One of the central elements of conservation agriculture is the minimum and/or no-till. The soil is not inverted and the crop residues are usually, but not always (e.g. Acevedo and Silva, 2003a) left on top of the soil aiming at maintaining and/or increasing the soil organic carbon, which is an essential element of soil sustainability (Rasmussen and Collins, 1991; Reicosky et al, 1995; Martínez et al, 2008).

No-till is part of a different way of doing agriculture, it responds to a new agronomy in which environmental sustainability is as central as crop yield. When the soil is not tilt and the crop residues are left on top of it, several agronomical consequences are generated. The crop residues are not incorporated into the soil and an accumulation and stratification of soil organic matter occurs (Rouanet, 1995; Valle et al., 2004). The residues slowly decompose, adding organic matter to the soil which changes its physical, chemical and biological properties. This type of agronomy/agriculture has rapidly extended around the world (Acevedo and Silva, 2003a) but it is only partially used in the Mediterranean environments, particularly if these are high yielding (e.g. Central Chile). In the Mediterranean

Figure 1. Climate Diagram for Talca, Chile (35°26' lat. S., 71°26' long. W., alt. 110 m.a.s.l)

Figure 2. Available soil water in a mollisol under continuous tillage (CT) and four years of no till (NT) in Central Chile (Reyes et al., 2002)

environments the summer rainfall is nil, therefore residue decomposition during this time period is limited by the lack of moisture and the crop residues stay on top of the soil for a long period of time, from December-January through April-May in the southern hemisphere, almost through the planting of the next crop, causing among others, physical problems to the planter (Acevedo and Silva, 2003a). At the break of autumn rainfall the residues start to decompose at a time when the temperatures are lower and limit the residue decomposition rate. The production of allelochemicals by the decomposing residues may also limit germination and cause seedling mortality, particularly in the case of legumes following cereals in the crop rotation (An et al., 2002; Silva, 2007; Ordonez et al., 2007). These problems do not occur in environments with summer rainfall where temperature and moisture are adequate for residue decomposition. In the high yielding Mediterranean environments usually the cereal straw has low value and the farmers finally decide to burn it, defeating the purpose of organic carbon incorporation into the soil to provide sustainability to the agricultural system.

The question is to what extent could variety traits help to overcome some of the constraints to no-till in Mediterranean environments.

No-Till the Effect of Crop Residues on the Soil

When the soil residues are left on top of the soil, many phenomena occur in the soil-residue interphase which are determinant for crop growth. These include the partitioning and balance of radiation, energy, water and carbon. The soil residues act as a physical barrier altering the mass and energy exchanges, the solar radiation does not arrive to the soil surface but it strikes the residues decreasing the direct radiation flux on the soil surface and hence the direct soil evaporation (Greb, 1983; Campbell and Norman, 1998; Carr et al., 2003) . As a result, more soil water is available for plants (Carr et al., 2003; Reyes et al., 2002). The rain drops fall on the residue dissipating their kinetic energy without affecting the soil structure. The soil water infiltration may improve due to the lower kinetic energy of the water reaching the soil surface, decreasing the water runoff and soil erosion (Acevedo and Martinez, 2003). The end result is that the soil water balance generally improves increasing the soil water availability to the plants (Figure 2) (Martinez, 2007; Reyes et al., 2002; Uribe and Rouanet, 2002). Black (1973) estimated that an additional 0,6 cm of available soil water resulted for each Mg of crop residue maintained on the surface of the soil in the northern Great Plains of the US. A relatively low amount of residue, covering approximately 40% of the soil is usually enough to decrease soil water erosion significantly. Finer residues such as wheat straw protect the soil better than thicker residues such as corn stalk (Acevedo and Silva, 2003a).

The lower solar radiation reaching the soil surface in no-till along with the higher water content of the soil decrease the mean soil temperature (Figure 2) lowering the rate of biological processes.

The main effect of the crop residues on the soil chemical properties is related to the increase of soil organic carbon in the form of soil organic matter. The organic matter provides essential nutrients such as N, P, K and micronutrients directly (Figure 4), stabilizes the soil structure and provides colloids that increase the soil cation exchange capacity (Green et al., 1995; Burgess et al., 2002; NREL, 2003; Mubarak et al., 2002, Martinez, 2007).

Time (month)

Figure 3. Maximum and minimum temperature at 2 cm depth in a mollisol under no-till (NT) and continuous tillage (CT) in Central Chile. There was a decrease in the maximum soil temperature of the soil under NT, having residues on top, along with a lower thermal amplitude than in CT. (Acevedo, unpublished).

Figure 4. Tillage system x soil depth x year interaction for

aerial reygrass (Lolium perenne) biomass production (Biomass) and some soil chemical properites in 2006-2007 season. NT and CT correspond to no tillage and conventional tillage treatments, respectively, for 0-2, 2-5, and 5-15 cm soil depth. SOC is soil organic carbon, NO3- is soil nitrate, P ext.

is the Olsen extractable phosphorus, K ext. is the extractable potassium (ammonia acetate 1N, pH 7), EC is the soil electrical conductivity and pH correspond to soil reaction (Martínez, 2007).

The initial availability to the crop of some nutrients, particularly N, is lower in no-till than in conventional tillage in spite of higher total N (Acevedo and Silva, 2003a). In an Entic Haploxeroll of Central Chile the N availability became higher in NT compared to CT only after 4 years of NT, when a new organic matter level, between 3.5 to 4.0 % in the top (0-2 cm) soil had been reached.

The microflora and microfauna of the soil increase with increasing organic matter content, mainly in the upper 5 centimeters. The microbial population of soils under direct drilling may increase by 30 to 40%. The combined and integrated action of fungi, actinomycete, bacteria and soil mesofauna transforms the organic matter coming from the crop residues into humus.

In synthesis, the crop residues on top of the soil may have multiple positive effects which include:

• Protect the soil against wind and water erosion.

• Decrease surface runoff.

• Increase soil water infiltration rate.

• Decrease direct soil water evaporation.

• Suply organic matter (C, N, P, S and others) to the soil.

• Upon decomposition provide organic colloids.

• Improve soil structure and aggregate stability.

• Avoid surface soil crusting.

• Improve soil aeration.

• Avoid extreme soil temperatures.

• Improve soil fertility.

• Improve the biological activity of the soil.

In the no-till systems, however, the beneficial effects of the increased organic matter are confounded with the effects of no tillage per se. Initially in the growing season the soil mechanical impedance is lower in conventional tillage than in no-till what decreases the growth rate of seedlings. Furthermore, the inappropriate use of no-till in heavy soils or in soils having unpaired drainage usually generates soil compaction (Figure 5). Martínez (2007) observed in an Entic Haploxeroll of Central Chile that plowing increased the soil macroporosity from planting to flowering. The soil under no-till had more stable aggregates but they were closer together forming a matrix throughout crop growth. As a result the soil water infiltration rate of this heavy soil under no-till was lower than under conventional tillage from sowing to flowering causing water pounding and the development of root fungal diseases such as root fusarium in wheat. Attention has to be given to water management and to farm machinery in terms of weight, tire width and air pressure as well as traffic in order to minimize soil compaction (Martínez, 2007). Medium to light

Impedance ^o cm'2)

0 i0 20 M » 60

Figure 5. Soil mechanical impedance profile in an Entic haploxeroll of Central Chile showing the effect of no-till (NT) as compared to conventional tillage (CT). The soil had been managed for seven years under NT (After Martínez, 2007).

texture soils cropped under direct drilling would not show the compaction problems and they usually will have an increased soil water infiltration rate and a decreased soil compaction as a result of an increased organic matter content and higher biological activity (Sheehan et al., 2004).

When the soil is compacted (clay, sandy clay) by machine traffic or the soil has a poor drainage, the soil water content may go beyond field capacity and anoxia may prevail.

No Till. Effect of Crop Residues on the Next Crop

Crop residues may produce physical, chemical and biological problems to the next crop._High yielding crops leave a high amount of residue in the field. A wheat crop yielding 7.0 Mg ha-1 leaves around 10 Mg ha-1 of crop residues, while an irrigated maize crop yielding 18 Mg ha-1 leaves 18 Mg ha-1 of corn residues. These amounts of residues may physically induce sowing problems to the next crop. The amount of water in the residue, its temperature and its chemical composition, particularly its C/N ratio determine the decomposition rate and hence the time of residence of the residue on top of the soil (García de Cortázar et al., 2003). As mentioned, in Mediterranean climates the crop residues stay dry for a long period of time, from harvest (December-January) to the break of autumn rains, April-May in the southern hemisphere, therefore, little decomposition takes place in that period in rainfed agriculture. The residues of annual crops left on top of the soil start decomposing at the start of autumn rains at a time when temperatures are relatively low and decreasing, what induces slow decomposition causing the crop residues to persist on the soil for a longer period of time. Table 1 shows C/N values for residues of various crops. Crops having residues with a high C/N ratio such as winter cereals will show a lower straw decomposition rate when compared to crops with lower C/N ratio in their residues such as legumes.

No-till in the presence of high quantities of crop residues on the soil makes the weed control more difficult due to a lower efficiency of soil-active herbicides, mostly used to control weeds in legume crops. The composition of dominant weeds, insects and pathogens change in no-till. The non inversion of the soil, lower soil temperatures, higher soil water content and the residues on top of the soil add to this effect. The pressure and genetic make-up of microorganisms that complete their development cycle having their sexual reproduction in the residues increase and plagues like slugs that thrive in the wetter environment provided by the straw increase markedly, particularly under high rainfall (1000 mm year -1 or more).

Table 1. Carbon / Nitrogen (C/N) ratio of residues of the main annual crops

Crop C/N

Wheat 60-90

Rice 80-90

Barley 80-90

Maize 50-60

Canola 40-50

Lupin 30-40

Lentil 30-40

Soil 10-12 Soil microorganisms 6-7

The straw decomposition generates chemical substances (allelochemicals) that may have an effect on the crop establishment of the next crop in the rotation. Residues of cereal crops being especially allelopathic to the legume crops such as lupine.

Crop Rotations

The result of a rotation of crops using no-till with crop residues left on top of the soil depend on several cropping factors including the species involved, the type, quantity and management of the straw, sowing date, changes in soil fertility and variety. Overall, the wheat crop is the most important annual crop in Mediterranean environments. It is also the crop that leaves residues on the field having the slower rate of decomposition owing to its high C/N ratio. Several crop rotations are common in Mediterranean environments such as wheat-oat, wheat-canola, wheat-lupine and wheat- irrigated maize.

Wheat-Oat Rotation

Even high amounts of wheat or oat residues (Figure 6) do not have an important effect on the establishment of these cereal crops as exemplified by wheat and oat straw on the establishment of wheat and oat in Central Chile (Table 2). The observed lower initial number of plants of the crop are compensated by fertile tillers such that the crop yield is not affected.

Table 2. Effect of residue management on the establishment of wheat and oat crops. Total amount of straw was 8-10 Mg ha-1 (adapted from Vidal and Troncoso, 2003)

Straw Management _Wheat_ _Oat

Establishment (plant m-2) Grain Yield(Mg ha-1) Establishment (plants m-2) Grain Yield(Mg ha-1)

Burned 368 6.75 373 5.73

Rowed 348 5.20 336 4.67

Chopped 318 6.37 254 4.85

Standing 307 6.17 271 4.95

LSD (0.05) 38 0.70 91 0.97

There is an increase in the incidence of some diseases in wheat when grown under NT. these include Root Fusarium, Septoria tritici, Helmintosporium tritici and Erysiphe graminis (Madariaga, 2003). Root Fusarium may become extremely important if the soil is compacted and the soil drainage is poor. The main weeds of this rotation are grasses such as Lolium multiflorum. Vulpia sp. and Bromus sp.

Wheat-Canola Rotation

The wheat straw decreases canola yield at a rate of 88 kg Mg-1 of wheat residue at planting of canola (Vidal y Troncoso, 2003). This is a mechanical problem caused by the wheat straw affecting the germination and establishment of canola which has a very small seed. An increase in the incidence of the disease Lepthosphaeria maculans = Phoma lingam in canola has been observed when wheat residues are left on top of the soil. Furthermore in the presence of wheat residues the canola crop is heavily infected by slugs with a severe damage when 2 slugs m-2 (D. reticulatum) are found in this crop (Acevedo y Silva, 2003a)._The wheat - canola rotation facilitates the control of broad leaf weeds (during the wheat crop) and of grasses (in the canola phase).

Time (years)

Figure 6. Simulated values of wheat residues on the soil for a rainfed wheat-oat rotation for Santiago (33oS) and Temuco (41 oS) (García de Cortázar, unpublished)

Time (years)

Figure 7. Simulated values of wheat residues on the soil for a rainfed wheat-lupin rotation for Santiago (33oS) and Temuco (41oS) (García de Cortázar, unpublished)

Wheat-Lupine Rotation

There is a strong depressing effect of the wheat residue on lupine yield. Above 3 Mg ha-1 of wheat straw the decrease of lupine yield is 20% Mg straw-1 (Vidal and Troncoso, 2003). Figure 7 shows a computer simulation of the accumulation of wheat residues in the wheat-lupine rotation at Santiago (33o S) and Temuco (41o S) under rainfed conditions. At year 4 of the rotation the wheat residues in Santiago reached a steady value of 6.5 Mg ha-1 and in Temuco 7.6 Mg ha-1.

Many lupin seedlings are lost immediately after emergence due to the incidence of Fusarium and Rhizoctonia sp. and to the allelopatic effects of the wheat residue on this crop. Table 3 shows that L. angustifolius cv Danja has a greater sensitivity than L. albus cv Rumbo when planted on wheat straw.

Table 3. Relative establishment (%) of L. angustifolius cv Danja and L. albus cv Rumbo on 5 and 1 Mg ha-1 of wheat residue. Values are relative to a control established without wheat straw (Silva, 2007).

Species Wheat residue

1 Mg ha-1 5 Mg ha-'

L. angustifolius cv Danja 62.3 b 30.9 d

L. albus cv Rumbo 85.9 a 35.4 c

LSD (0.05) 4.2

An option to avoid allelopathic effects is to delay the sowing of lupin towards the end of winter planting on a more decomposed cereal residue. This allows a better lupin establishment, particularly in the case of L. angustifolius (Figure 8).

Pre-emergence herbicides are used to control broad leaf weeds in legumes such as lupin. Carrasco (2003) evaluated using Linuron, Metribuzine, Simazine and Alaclor on the yield of L. albus cropped on NT and CT. The herbicides had to be chosen according to the tillage system being Linuron the best herbicide in NT and Metribuzina in CT .

Wheat-Maize Rotation

Maize is a summer crop usually planted around six months after the wheat harvest. The wheat straw is substantially decomposed when the maize is planted, therefore it does not cause problems to the maize establishment (Figure 9).

On the contrary, wheat plantings (May) immediately after a medium yielding (14 Mg ha-1) grain maize harvest on chopped maize straw have decreased the number of wheat plants established by 50%. Sweet corn, on the other hand, leaves a lower amount of residue (5 Mg ha-1) than grain maize, with lower lignin content and a longer time period between the harvest of sweet corn and the wheat planting not affecting the wheat establishment.

April July

Planting time

Figure 8. Relative establishment of L. albus (a) and L. angustifolius (b) under NT with respect to the establishment in a soil in which the residue had been burned. Early (April) and a late (July) sowings in the foothills of the Andes in Chilean Region VIII (Acevedo and Silva, unpublished).

Figure 9. Maize yield under conventional tillage CT and no-till NT in Central Chile (Martínez, 2007).

We have observed that during the first four years of the wheat-maize rotation there is a decrease in N availability which is particularly expressed in the wheat phase of the rotation. The reduction in wheat yield has been as high as 34% of the yield obtained under CT and is mainly due to a decrease in the number of grains per unit area. This period coincides with the highest amount of carbon sequestration by the soil in NT. On the average (10 year) the soil fixed 500 kg C ha-1year-1 mainly in the form of humus (C/N @10/1) what implies 50 kg N sequestration ha-1year-1. After 4 years of NT the N availabilty was restored and even increased when the soil organic matter has reached a new equilibrium.

Ideotypic Traits of Wheat for No-Till

Due to the changes in the soil physical, chemical and biological properties and the effects of crop residues on the next crop, the agronomy of a crop under no-till differs from conventional tillage. Furthermore, the varieties developed for conventional tillage systems do not necessarily have the same performance under no-till and specific genotypes are recommended for no-till (Chevalier and Ciha, 1986; Yang and Baker, 1991; Tillman et al, 1991). The reasons for the GM interaction include soil mechanical impedance, diseases (type and intensity), soil temperature, anoxia, allelopathy and weed control.

Soil Mechanical Impedance and the Rhizosphere

Compacted soils under no-till show an increase in bulk density (Ball-Coelho et al., 1998; Lampurlanés and Cantero-Martínez, 2003), lower soil temperature (Drury et al., 1999), and a decrease in oxigen diffusion rate (Russell, 1988). As a result no-till reduces the wheat growth rate (Braim et al., 1992; Kirkegaard et al., 1995). The increase in soil mechanical impedance negatively affects the growth of roots (Watt et al., 2005), particularly during the initial growth phases (Lampurlanés et al., 2001) due to a lower absorption of water and nutrients (Qin et al., 2006). The root length density, however, is higher in the surface soil of no-till (0-5 cm) when compared to CT (Wilhelm and Wortmann, 1996; Martínez et al., 2008) due to a higher fertility (Franzluebbers and Hons, 1996; Thomas et al., 2007) and soil organic matter (Havlin et al., 1990, Salinas-García et al., 1997, Franzluebbers, 2001), what in turn favors microbial activity (Anderson and Domsch, 1989; Renz et al., 1999) nutrient cycling and root growth. Furthermore, in hard soils wheat roots are more susceptible to Fusarium and Rhizoctonia (Gill et al., 2004).

Vigorous wheat genotypes appear to grow better in no-till soils as shown by Watt et al. (2005) who compared two bread wheat genotypes, "Janz" (conventional) and a line selected for its vigorous leaf growth, "Vigour 18". Both genotypes showed distorted roots and shorter apices in NT vs. CT soil. The roots of Vigour 18, however, grew 39% faster, were thicker and were less distorted than the roots of Janz in the NT soil. The shoot growth of Vigour 18 was 64% faster than Janz in NT.

When anoxia is a problem varieties having an over expresión of aerenquima in their roots may be indicated (Malik et al., 2003), or transgenics allowing the subsístanse of the plants in flooded soils, similar to the gene SubIA with the ethylene response factor found in rice (Xu et al., 2006). Wheat and barley, two species intolerant to anoxia, if subject to anoxia at the seed state adopt a quiescent state which does not allow the growth of the coleoptile (Perata and Alpi, 1993). Unfortunately the wheat and barley seeds rapidly loose viability under anoxia due to fermentation of starch (Guglielminetti et al., 2001; Perata et al., 1997). An interesting alternative is the cross between Hordeum marinum (sea barley grass) and wheat to produce hybrids which are able to tolerate flooding and salinity (Mc Donald et al., 2001; Colmer et al., 2006).

Weed Control

A different strategy to weed control allowed the expansion of no-till of crops like maize and soybean to millions of hectares. The basic idea is to create varieties resistant to an easily degradable wide spectrum herbicide like glyphosphate. In those countries where transgenics are not allowed, the use of imidazolinone resistant varieties is playing a similar role. New spring canola varieties are being produced which are resistant to imidazolinones) allowing an excellent weed control in the canola crop grown under no-till. Similar to canola there are maize hybrids resistant to imidazolinones which allow a good weed control. The IMI or Clearfield hybrids (resistant to imidazolinones) have even shown an increase in grain yield when planted on wheat straw (Table 4).

Table 4. Biomass and grain yield of the maize hybrids Mexico IMI (M. IMI) treated with imidazolinones in NT in Central Chile (Acevedo and Silva, 2003b)

Treatments Biomass (Mg ha-1) Yield (Mg ha-1)

M. IMI width out weed control. 22.3 11.1

M. IMI (D1) 28.2 13.5

M. IMI (DD2) 30.9 16.4

LSD (0.05) 5.7 4.1

1 Dose A of imidazolinona (euro-lightning)

2 Dose B of imidazolinona (euro-lighting)

Diseases

Many of the most relevant pathogens in cereals, including fusarium and septoria in wheat belong to the ascomycetes fungi. These fungi complete their life cycle (sexual phase) in the residue of the crop that infected in their pathogenic (asexual) phase, generating new types that may be more virulent than the original pathogen (Madariaga, 2003).

Much work is needed to decrease the infection of soil borne pathogens on crops like cereals and legumes. Major problems may be caused by rhizoctonia and root fusarium at the seedling stage, and root fusarium in cereals undergoing some degree of anoxia at the flowering stage.

Allelopathy

When the residue of some winter cereals (oat, wheat, barley, rye) is in a relatively high amount (more than 5 T ha-1) at sowing time and it has not undergone decomposition due to lack of moisture, it is possible that phytotoxic compounds may generate along with the first autumn rains. The compounds are leached into the soil producing allelopatic symptoms in the seedlings of the next crop (Guenzi et al., 1967; Kimber, 1973) in the rotation. particularly if it is a legume such as lupine (Silva, 2007).

A plausible solution to this complex problem is through crop improvement, selecting cereals genotypes having a lower degree of allelopathy in their straw or selecting legumes which are tolerant to allelopathy (Silva, 2007). This idea seems to be supported by two pieces of evidence: 1) There is genetic variability in the allelopathic capacity of some crops included wheat (Guenzi et al., 1967; Kimber, 1967; Ben-Hammouda et al., 1995; Ahn and Chung, 2000; Olofsdotter, 2001). 2) There is genetic variability in the tolerance to allelopathy of some crops including lupine (Herrin et al., 1986; Bruce y Christen, 2001; Silva, 2007).

Silva (2007) used 50 wheat genotypes and 16 lupine genotypes and showed in field and laboratory trials that the wheat residue had allelopathic effects on L. albus and L. angustifolius. The allelopathic capacity of the wheat

Table 5. Synthesis of the main problems of no tillage with residues on top of the soil and plausible solutions in rotations involving wheat, canola, lupine and maize.

Problem (Severity1)

Plausible Solution

Crop establishment after maize (*) Mecanical Wheat Nitrogen deficiency (**)

Weeds (**)

Diseases (**)

Crop establishment (**) Mechanical Canola Slugs (**)

Weeds (*)

Crop establishment (***) Diseases

Lupine Allelopathy

Slugs (**) Weeds (**)

Nitrogen deficiency. (**)

-Reduce the quantity of straw (rowing, baling, animals, biofuel).

-Increase N fertilzer by (30%).

-Use wheat genotypes with a higher N use efficiency.

-Rotation with oil crops and / or legume crops.

-Development of wide spectrum herbicide tolerant wheat genotypes.

-Use of tolerant varieties.

-Avoid soil compaction (anoxia).

-Use of fungicides.

-Reduce the quantity of straw (rowing, baling animals, biofuel). -Rowing of the residue plus molluscicide. -Resistant varieties? -Rotations

-Use of clearfield varieties.

-Avoid soil compaction (anoxia). -Fungicide.

-Reduce the quantity of straw (rowing, baling animals. biofuel).

-Change the sowing date from autumn to spring.

-Use of varieties having lower sensitivity to straw.

-Rowing of the residue plus molluscicides.

-Use of more efficient soil-active herbicides in NT e.g. Linuron.

-Development of varieties resistant to wide spectrum herbicides.

-Increase N dose (30%).

-Develop hybrids having a higher N use efficiency

: low. **= moderate. *

= high

genotypes, however, had a high GxE and low heritability, therefore she selected wheat genotypes (high and low) having a more stable allelopathic capacity across environments and identified L. angustifolius as a more sensitive species to the presence of wheat straw, sensitivity that was associated to a lower lupine germination rate in the presence of wheat exudates. The interaction between wheat genotype and lupine species was significant hence the selection of less allelopathic wheat genotypes had to be done independently for L. albus and L. angustifolius. Intraespecific differences in allelopathic sensitivity to the wheat extracts were also found for both lupine species. She also showed that summer rainfalls may reduce the allelopathic effect considerably and identified an inhibitory effect of the soil previously cropped to wheat on lupine establishment.

Synthesis

The main constraints to zero tillage in Mediterranean Environments and plausible solutions expressed in this document are shown in Table 5

Acknowledgments

Financial support for the Chilean work presented in this paper was obtained by the research projects FONDECYT N° 1050565, FONDEF D99I1081, DI-University of Chile, SIRDS -SAG-INDAP- University of Chile Convenio on No-Till and FIA.

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Breeding for improved adaptation to conservation agriculture

improves crop yields

Richard Trethowan1*, Yann Manes2 and Tariq Chattha1

1 University of Sydney, Plant Breeding Institute, PMB 11, Camden, NSW 25702Intemational Maize and Wheat Improvement Center (CIMMYT). Apdo. Postal 6-641, Mexico D.F., Mexico (*Email rtrethowan@camden.usyd.edu.au)

Food production must be increased to meet projected global demands. However, declining investment in agriculture, reduced inputs and an increasingly variable production environment make this a significant challenge. Combining resource efficient agronomy with better adapted crop cultivars will be vital if the productivity of the world's food producing systems is to be maintained or increased. The existence of genotype x resource conserving crop management practice interactions, traits controlling these interactions and breeding strategies that can be used to improve yield under conservation agriculture are discussed.

The adoption of reduced or zero-tillage reduces erosion, improves soil structure, minimizes costs and more importantly, enhances the water use efficiency of cropping systems. However, even when zero tillage is the common practice at the farm level, often crop breeding programs do not evaluate and select segregating germplasm in conservation agricultural systems. To compound the impact, in many developing countries advanced materials are evaluated for yield and adaptation on research stations under conventional or complete tillage. These data are then used to release cultivars to farmers. In countries such as Australia, breeders have historically selected segregating materials under conventional tillage, but tested their advanced products on-farm in multi-environment trials before release to farmers, thereby sampling farmer practices in time and space.

Yield improvement is the primary goal of all crop breeding programs and to a large extent breeders use genetic resistance to maintain yield in the face of changing disease virulence. However, achieving significant improvements in underlying yield potential is considerably more difficult. The historic rate of yield increase of 1% per year since the Green Revolution (Trethowan et al., 2007) is a combination of genetic and agronomic interventions (Bell et al., 1995). The development of short-statured wheat and rice cultivars allowed farmers to apply more N, the most basic of all agronomic interventions, resulting in significantly improved yield. The semi-dwarfing genes radically changed plant morphology, significantly improving harvest index. However, it is unlikely that such dramatic improvements in yield will be observed in the future and gains are likely to continue to be cumulative over time.

Reports indicate that water will become increasingly limiting in many cropping systems (Trethowan et al., 2005). Clearly, combining water and resource conserving agricultural practices, such as zero-tillage, with better adapted, more water-use-efficient cultivars will enhance the overall productivity and profitability of most cropping systems. Plant breeding can contribute to this improvement if genotype x farming system interactions can be exploited. This paper reviews the extent of these interactions and their genetic control and examines possible strategies that plant breeders may use to improve cultivar adaptation to conservation agriculture.

(I) Evidence of Genotype * Farming Practice Interactions in Crop Plants

The existence of genotype x tillage practice interaction is critical if plant breeders are to make progress in the development of better adapted cultivars. There is little published evidence of such interactions as much of the early work was conducted by agronomists using relatively small numbers of genotypes, all of which were developed under conventional tillage. Cox et al (1991) found no interaction in wheat. However, in a later study utilizing a more diverse range of wheat genotypes, Gutierrez (2005) found significant interactions for yield and industrial quality across vastly different environments. Non-significant interactions have been reported for barley (Ullrich and Muir, 1986), sorghum (Francis et al., 1984), rice (Melo et al., 2005) and soybean (Elmore, 1990) and conflicting results obtained for maize (Brakke et al 1983; Newhouse, 1985). In a recent study, diverse wheat genotypes were grown under contrasting tillage regimes in Australia and Mexico and no significant genotype x tillage interaction was noted (R. Trethowan and Y. Manes, unpublished data). However, in most environments the mean yield was significantly greater under zero-tillage highlighting the advantages of conservation agriculture in moisture limited environments

Table 1. Mean yield (kg ha) of tillage treatments of trials grown in Australia and Mexico in 2007 & 2008

RK 2007f

RK 2008

GV 2007

GV 2008

Zero-tillage Complete till

Zero-tillage Complete till

1945 a 1658 b MEXRI 2007 4350 4120

3145 a 2604 b MEXFI 2007 6210 5930

1359 a 1139 b MEXDR2008 3340 2730

2561 a 2647 a MEXRI 2008 4260 3820

MEXFI 2008 6440 6430

t RK = red kandosol soil at Narrabri, Australia; GV - grey vertosol soil at Narrabri, Australia; MEXDR = drought trial at Ciudad Obregon, MEXRI = reduced irrigation trial at Ciudad Obregon, Mexico; MEXFI = fully irrigated trial at Cd. Obregon, Mexico

Figure 1. Results of soil moisture from drought conventional and zero tillage trials grown in Mexico in 2007

(Table 1). Moisture samples taken from the same trial in both CT and ZT drought treatments in 2007 confirm that zero tillage keeps more soil moisture than conventional tillage treatment, as expected (figure 1).

The non-significant genotype x tillage practice interaction may reflect a lack of genetic diversity for those traits conferring adaptation to conservation agriculture in the materials tested.

(II) Traits to Consider When Developing Crops Better Adapted to Conservation Agriculture

Once the existence of a genotype x farming practice interaction has been established, the plant breeder requires easily measured traits to drive the selection process, particularly in the early generations when the numbers of progenies from each cross combination are large. Coleoptile length (Rebetzke et al., 2007; Trethowan et al., 2001) and thickness (Rebetzke et al., 2004), emergence from depth (Trethowan et al., 2005), seedling vigour (Liang and Richards, 1999), rate of stubble decomposition (Joshi et al., 2007), root depth (Reynolds and Trethowan, 2007), allelopathy (Bertholdsson, 2005), N-use-efficiency (Ginkel et al., 2001), disease resistance (Trethowan et al., 2005) and seedling temperature tolerance (Boubaker and Yamada, 1991) are all considered important traits that influence crop establishment in zero-till systems.

Clearly, some of these traits are interrelated, such as emergence from depth and coleoptile length. However, not all the variance observed in coleoptile length explains emergence and stand establishment (Rebetzke et al., 2007) hence we can consider them to be independent characters. Although many of the references for these traits pertain to wheat, the same principles of adaptation apply to all crops.

The difficulties of applying N in conservation agricultural systems can result in N deficiency (Hobbs et al., 1998) and selection for improved N-use-efficiency can improve general adaption (Ginkel et al., 2001). In some farming systems weed growth during early crop development can limit yield and selection for cultivars with increased early vigour or greater early biomass development will reduce weed competition. In addition, allelopathy can be a significant constraint and genetic variability for response to weed infestation does exist and can be exploited (Bertholdsson, 2005). Some Australian grain growers consider that the high levels of surface residue from previous crops makes these systems difficult to manage (R McClean, personal comm.). However, variability among wheat cultivars for the rate of stubble decomposition does exist and could enhance the acceptance of such cultivars (Joshi et al 2007).

Thermo-tolerance will also improve cultivar adaptation to early season temperature fluctuations, as the rate of emergence and general seedling vigour are influenced by temperature fluctuations. Good early vigor combined with vegetative frost tolerance is advantageous in areas where cold temperatures come rapidly after planting and early frost can occur. Nevertheless, changes in disease patterns linked to stubble retention remain the primary constraint to cultivar adaptation to conservation agriculture. The introduction of zero-till tends to increase the incidence of wheat diseases such as crown rot (Fusarium pseudograminearum), tan spot (Pyrenophora tritici-repentis) which over summer on the surface residues (Mezzalama et al, 2001), or fusarium head blight in the case of wheat rotating with maize. Nevertheless, significant genetic variation for these diseases exists in the wheat gene pool and although the inheritance may be complex, as in the case of crown rot resistance, it is possible to make significant progress in genetic resistance.

Except in the case of disease resistance where the impact on yield is obvious, most of the other traits mentioned above affect only the early stages of the crop cycle. Their impact on yield under CA practices is only putative, and remains to be confirmed. This could be done as follows:

• Evaluation of elite lines showing differential response under conventional tillage and zero tillage for expression of the traits mentioned above.

• Collection of materials which show extreme expression of the traits mentioned, followed by head-to head testing under zero tillage and conventional tillage.

• Creation of isogenic materials for traits such as coleoptile length to study responses to zero and conventional tillage.

(III) Breeding Strategies to Improve Adaptation to Conservation Agriculture using Wheat as an Example

The first step in any breeding program is to assemble sufficient genetic variability for the key target characters. There is limited variability within the primary wheat gene pool for the traits discussed in section II. However, the probability of success is improved if genetic variability can be increased. The landraces and synthetic wheats, produced by re-synthesizing hexaploid bread wheat by crossing both modern and ancestral tetraploid durum wheats with Aegilops tauschii, the donor of the D-genome (Mujeeb-Kazi, 2006), offer significant genetic diversity that can be crossed directly to modern bread wheat. Both these sources provide useful variability for root depth (Reynolds et al, 2007), emergence from depth (Trethowan et al, 2005), alternative sources of dwarfism that do not significantly reduce coleoptile length (Rebetzke et al, 2007), early vigour (Liang and Richards, 1999), increased specific leaf area (Olesen et al., 2004), increased seed size (Liang and Richards, 1999), improved water and N use efficiency, better seedling tolerance to temperature extremes and improved disease resistance.

Transgenes conferring herbicide tolerance can also improve crop adaptation to zero-tillage as they effectively control weed competition and need only to be deployed in one element of the crop rotation. An example is the deployment of herbicide tolerant soybean in rotation with wheat, very common in Argentina for example; weed growth in the subsequent wheat crop is significantly reduced (Cook, 2006).

A possible breeding plan for the development of wheat cultivars with improved adaptation to zero-tillage is outlined below.

I. Screen adapted and unadapted germplasm for response to conservation agriculture measuring yield, disease and product quality to determine the extent of genotype x tillage interactions.

Locally adapted cultivars, introductions from CIMMYT and or regions where conservation agriculture is dominant, landraces and synthetic derivatives are tested under contrasting residue management practices. Yield and product quality are determined and disease screening is conducted concurrently.

II. Identify/introduce parental materials that represent extreme expression of the traits in section II, assuming these traits really improve yield under CA practices.

Screen available germplasm for trait expression and acquire additional diversity from gene banks and the published literature. Assess all materials head-to-head and select those with the most extreme expression of the trait in the best agronomic and disease resistance background.

III. Combine genetic diversity in crosses with emphasis on adaptation to the target conditions

Genetic diversity for the key characters in section II must be combined with those traits considered key to the target region. These include characteristic such as yield potential, stress tolerance, product quality and disease resistance. This may require backcrossing to an adapted parent or top-crossing using the adapted line as the top-cross parent. In some cases it may require multiple cycles of crossing and selection.

IV. Implement a selection strategy to identify genotypes with good emergence and establishment and disease resistance in a zero-tillage system

Large segregating populations (F2 - F5) are screened and selected under zero-tillage. In crosses with significant variability for coleoptile length, additional pressure on emergence may be applied by deep planting these generations. If possible, field evaluation for adaptation to zero-tillage should be combined with disease inoculation. A selected bulk or modified pedigree scheme are effective methods that can be used to advance each generation.

V. Evaluate fixed lines for response to conservation agricultural practices in the target region.

Once fixed lines have been selected, generally by selecting individual plants or spikes in the F5 of F6 generation, they are screened for disease resistance prior to testing in multi-locationl yield trials. These trials will represent a range of conservation agricultural practices across the target region and are usually conducted over several years. Grain yield, product quality and disease resistance are key selection goals.

VI. Select those materials with high yield, appropriate quality and stable performance across farmer practices within the target region for release.

A significant portion of the success of any plant breeder lies choosing the correct parents and the importance of Step III cannot be overestimated. Attempting to combine too much variability is a recipe for failure as it becomes impossible to grow sufficiently large enough segregating populations to select adapted materials combining all the targeted traits. A stepwise process, where traits are combined through successive cycles of breeding, will enrich the gene pool and in time the adaptation of the derived cultivars. Of equal importance is the management of gene frequency through appropriate selection pressure in the segregating generations. For instance, deep planting is a quick and easy way to select for longer coleoptiles and better emergence, but will work only in crosses where the right genetic variability exists. Selection in zero tillage with heavy residues will probably improve emergence although it is not clear how many successive generations of selection are necessary to do so. As in any cultivar development program, the exposure of segregating generations to diseases, particularly the rusts of wheat, is critical. Once rust resistance has been established, inoculation of materials for zero-till specific disease such as tan spot and crown rot will increase the proportion of fixed lines carrying all the desired characters needed for release to farmers.

Conclusion

This paper focuses on genetic aspects of adaptation and assumes an optimized farming system. In reality this is never the case and genetic improvement and improvements in crop management will proceed hand in hand. Optimizing the choice of cultivar and resource conserving farming practice can improve the adaptation and yield potential of traditional crops. However, as climate and markets change, the distribution of crops regionally may alter if the productivity and profitability of today's farming systems are to be maintained

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Adapting Wheats to Zero Tillage in Maize-Wheat-Soybean Rotation

System

Man Mohan Kohli* and Jorge Fraschina

BIOCERES, Moreno 878-4th Piso (S2000DKP) Rosario, Argentina; Instituto Nacional de Tecnologia Agropecuaria, INTA, CC 21, 2850 Marcos Juarez, Cordoba, Argentina

Adoption of conservation agriculture, especially zero tillage and associated practices, in the Southern Cone region of South America have revolutionized the cereals and oilseeds production systems over the last two decades. Of the total 50 million hectares under zero tillage in the region, there are approximately 20 million hectares sown to grain crops in Argentina, up from less than one million hectares a decade ago. Since wheat is an export commodity for Argentina, it became important to adapt its varieties and germplasm to the newer set of cultural practices. The evaluation and exploitation of genetic variability have been for the following adaptation characteristics: uniformity of early crop establishment associated with soybean/maize stubble; need for high or low tillering capacity and plant height depending on the number of years of zero tillage and/or the rotation followed; resistance to frost damage in the vegetative (tillering) stage; stronger straw strength; synchronous heading; resistance to foliar and spike diseases especially tan spot, septoria leaf blotch and fusarium head blight; rapid grain filling or quick finish to allow early seeding of the following crop; lack of late tillers; higher yield potential etc. While it has been difficult to establish a genotype x tillage interaction in every situation, superior genotypes for either tillage environment can be observed. Their identification based on the traits mentioned above is a key to developing newer wheats adapted to zero tillage conditions. To achieve this goal, the breeding programs need to adapt to the dynamics of the physical, chemical and biological changes occurring in the soil system which permit the crops to achieve ever increasing yields as a result of higher water holding capacity and accumulated soil fertility over time.

Key words: Wheat, Triticum, Breeding, Adaptation, Zero Tillage, Conservation Agriculture, Lessons

The world cereal need of 2.5 billion metric tons by the year 2020 projected by the International Food Policy Research Institute (Rosegrant et al.., 2001) or of 2.8 billion tons by the year 2030 as projected by the FAO (FAO, 2002) is not a far fetched target to be met with the technology available at present and others that are under development. However, these production increases are not likely to occur by bringing increased area under agriculture as done in the past. Most of the opportunities to bring new agricultural land under cultivation have already been exploited. While there are large unexploited tracts of land in Africa and South America, only some of it will eventually come into agricultural production. Bringing world's unexploited but potentially cultivable lands into agricultural production poses formidable challenges not only in terms of sustainable technologies but also needs expensive infrastructure development.

Besides global challenges on food production, the farmers in the Southern Cone countries of South America (Argentina, Bolivia, Brazil, Chile, Paraguay and Uruguay) faced traditional challenges, such as soil erosion or degradation, the loss of cropland to non-farm uses, an ever increasing demand for production inputs, the volatile world food prices and a dire need to produce more but with sustainable technologies. Intense cropping without proper rotations, lack of fertilization and exploitive soil tillage were major elements of soil degradation and deterioration of the best agricultural areas of the region. Soil erosion and a decreased fertility were major factors for stagnation of Argentine cereals and oilseed production between the 1940s and 1970s. These tasks required reshaping the region's farming systems to allow simultaneous achievement of a higher level of productivity, sustainability and profitability in order to be adopted widely. The production revolution seen over the last two decades is primarily based on the soil and water conservation programs.

Adoption of conservation agriculture, especially zero tillage and associated practices have not only helped increase the cereals and oilseeds production but also improved the farm economy by making agriculture a profitable enterprise. As a result, the area under zero tillage in the region increased from less than one million hectares in 1989/90 to almost 50 million hectares in 2005/06 (Fig. 1). During the same period the combined production of wheat, maize and soybeans almost tripled from 76 million tons to over 230 million tons (FAO, 2008).

In Argentina, the rapid adoption of conservation tillage practices combined with adequate rotation and fertilization as well as introduction of Round Up resistant soybean varieties have resulted in a historic increase in grain production. Almost two thirds of the 30 million hectares sown to grain crops in Argentina are under zero tillage and the

Figure 1. Increase in the area under zero tillage and combined production of wheat, maize and soybeans

in the Southern Cone countries

Figure 2. Evolution of Argentine cereals and oilseed area and production, 1941-2007 (SAGPyA, 2008) production of cereals and oilseeds has increased from 40 million tons to almost 100 million tons in a decade (Fig.

Considering that zero tillage was introduced, modified and promoted by the farmers all over the region, it took some time before the researchers realized its benefits and adopted the technology on their experimental fields. Benefits from zero tillage practices are now well recognized including reduced erosion, improved soil structure and infiltration, reduced runoff and water conservation etc. From the stand point of crop improvement, varieties developed under conventional tillage have been used till now but the agronomic characteristics that provide better adaptation to zero till conditions are continuously being identified.

Inclusion of Wheat in the Agricultural Rotation

In the drier parts of the wheat region, the precipitation towards the end of the summer crops (maize and soybean) leaves an excess of water in the soil thus providing a unique opportunity to grow a winter crop and add more stubble cover on the soil. A wheat crop is seen to use this water very efficiently by transforming it into biomass and grain and also provide well distributed stubble with a high C/N ratio (Fraschina et al., 2008). Another less seen contribution of the winter cereal crops to the system is their root mass. The characteristic root system of wheat conducts a true "biological tillage" by breaking the compaction caused by the transit of the machinery during harvest of the summer crop. Gerster et al., 2006, believe that wheat, with its stubble cover and root mass, contributes to an adequate implementation of the zero tillage system. In general, the quantity of stubble a wheat crop will leave on the soil surface depends more on the grain yield of a variety than the variety per se. However, at same yield level, there are some varieties that leave relatively more stubble than others (Fraschina et al., 2006).

Given that most of the wheat crop in Argentina and other parts of the region is grown in rotation with soybean and maize, the knowledge of specific traits needed to improve its adaptation has led to large scale germplasm screening. Some of the lessons learnt in the process and key germplasm characteristics identified under zero tillage are discussed in this paper.

Agronomic Characters of Importance under Zero Till Conditions

Early Plant Vigor and Crop Establishment

The maintenance of crop residue on the soil surface is one of the major components of zero tillage in the Southern Cone region. Depending on the quantity and quality of the crop residue and its degradation before the seeding of wheat crop, early crop vigor and stand establishment have become important characteristics to screen for. In a series of experiments, Abbate et al. (1997) observed significant genetic variability among Argentine wheats for early crop growth. At mid tillering stage the average dry weight of the foliar mass of a variety varied between 500 and 745 g/m2. While the purpose of the study was to measure radiation use efficiency (average 2.5 MJ/m2/d1) and rate of crop growth (average 25 g/m2/d1) to correlate it with the total number of grains/m2 and grain yield, these differences have become very useful to identify varieties with much needed early ground cover in the dryland agriculture.

Given that higher water accumulation under zero tillage allows the farmers in Argentina to seed facultative or early winter wheats, a new set of experiments is underway to determine similar variability for early vigor in this germplasm (Abbate pers.comm). Initial results presented in the Fig. 3. demonstrate that varieties with winter growth habit (BAG 21, BIO 2004, Nogal and JN 5007) differ significantly in their capacity to produce early biomass on per plant or per plot basis. Higher biomass production per plant of the intermediate or facultative types at the tillering stage also coincided with higher biomass production per plot and seemed to be genetically controlled.

Dry weight (a/m2) ♦ Dry weight (mg/plant)

BAG11 BAG21 BIO 2004 BI03000 BI03004 NOGAL JN05007

Figure 3. Differences among wheat varieties for total biomass production at mid tillering stage

Uniform crop establishment in fields with higher quantity of stubble, especially after maize, has been another common problem. The difficulty arises from the lack of seed placement at uniform depth, often on the stubble and not in contact with the soil, thereby promoting frost damage in the seedling stage. While a large kernel size would theoretically provide nutrition for a longer period of time to reach the first leaf through coleoptile stage, no such differences were observed. It seems to be a problem for the engineering companies to solve with new seeding machines that are capable of providing a uniform stand even under higher stubble situations.

Tillering Capacity, Plant Height and Stubble Yield

Depending on the number of years of zero tillage, crop rotation schemes and climatic conditions of a region, the need for high or low tillering capacity and stubble yield has become apparent. In its initial stages of adoption or for the lack of maize or other cereal crops in the rotation in the warm dryland regions, the fields under zero tillage retain very little quantity of crop residue. As a result, wheat varieties with higher tillering capacity and biomass production (such as tall dwarfs) were better adapted than lower tillering varieties. However, as the stubble retention on the soil surface increases with the passage of years and/or from the inclusion of cereal crops in the rotation system, lower tillering varieties are preferred because wheat stubble not only decomposes slowly but also provides a hot bed for the disease pathogens.

Wheat Group of INTA, Marcos Juarez, conducted two on farm trials in the drier part of the Pampas region during 2006-07 to demonstrate significant differences in stubble production associated with high or low tillering capacity and plant height among spring and facultative wheat varieties. Both farms, in Monte Buey and Corral de Bustos, have used zero tillage for almost two decades. The rotation followed in Monte Buey, wheat-soybean II/maize/ soybean I, represents a crop of wheat every third year; while that in Corral de Bustos, wheat-soybean II/maize, represents a wheat crop every second year. The data presented in the Table 1 shows that the facultative wheats, seeded early, retain marked differences in the stubble they leave on ground at the harvest time at both locations. However, in the case of spring wheat varieties these differences are only clear if the crop comes on the maize stubble (Corral de Bustos), representing higher water profile in the soil. Spring crop seeded on the soybean stubble (Monte Buey), meaning less water in the profile at the time of planting, leads to more competition among higher tillering germplasm. As a result there is more tiller loss in this germplasm compared to low tillering varieties which end up producing more stubble and even grain yield.

Table 1. Tillering capacity, plant height and stubble yield of selected facultative and spring wheats at two locations in the dry Pampas region of Cordoba Province, Argentina

Varieties Tillering capacity/ Plant height Stubble (tons/ha) Monte Buey Corral de Bustos (wheat on soybean stubble) (wheat on maize stubble)

Facultative wheats

Baguette 11 Low/Short 8.6 11.4

BI0INTA3004 Interm./Interm 11.7 11.5

BI0INTA3000 Interm./Tall 11.6 12.1

Klein Gavilan High/Tall 13.2 12.7

Spring wheats

Baguette P 13 Low/Tall 11.8 9.8

Klein Tauro Low/Tall 11.9 9.2

BI0INTA1001 High/Interm. 10.2 12.7

Cronox High/Interm. 10.7 10.7

Resistance to Frost Damage in the Vegetative (tillering) Stage

Resistance of genotypes to changes in high and low temperature is a critical trait for germplasm adaptation to zero tillage in the Southern Cone region. There are common spells of high temperature regimes (high 20s and low 30s C°) of several days in the middle of the winter season that promote higher crop growth. Whenever such a period of lush growth is followed by a sudden fall in the temperature leading to frost, severe loss (burning) of biomass in the susceptible germplasm is observed. There are significant varietal differences in both facultative and spring wheat germplasm. In addition, these differences are further accentuated by the type of rotation used and the amount of crop residue on the soil surface which modifies the duration of the low temperature. In general, a susceptible wheat variety is more likely to suffer severe damage following a maize crop (higher crop residue) than a soybean crop which leaves less stubble.

A field classification of major Argentine wheat varieties for their reaction to early frost damage is presented in the Table 2. Although farmers have been seeding both resistant and susceptible wheat varieties through the years, their strong inclination to add maize or some other cereal crop to the rotation system (to generate more stubble) in the drier regions is slowly changing the varietal picture in favor of frost resistant varieties. Therefore, breeding for frost resistance has become an important goal in the wheat program. A genetic analysis of the frost resistant germplasm shows that most of them have some vernalization requirement Fu et al. (2005). However, varieties carrying similar genetic combination for known vernalization genes (Vrn) still show marked differences in the frost resistance indicating thereby the presence of additional modifying factors or other frost resistance genes in the germplasm.

Plant Height and Stronger Straw Strength

Heavy ground cover, as one of the key components of zero tillage, is promoted in the region not only to reduce the erosion but also to help retain higher humidity in the soil profile. Additional dynamics of the physical, chemical

Table 2. Field classification of major Argentine wheat varieties to frost reaction

Facultative wheats VrnA1* VrnB1 VrnD1 Frost resistance** Spring wheats VrnA1 VrnB1 VrnD1 Frost resistance

ACA 303 w s s S B 75 ANIVERSARIO S

BCHACARERO s s s S BAGUEIIE9 s w w MR

BGUAPO w s w R BAGUETTEP13 w w s S

BAGUETTE 10 s w w MR BIOINTA 1000 w s w S

BAGUEIIE 11 s w w S BIOINTA1001 w s s MR

BAGUETTE 19 s w w MR BIOINTA 1002 w w s R

BIOINTA2002 w s w MR BI0INTA1004 s w w MR

BIOINTA3000 s s s S CRONOX w s s MR

BI0INTA3003 w w w R I CHURRINCHE s s w S

BIOINTA3004 s s s S I CONDOR s s w S

KL CARPINCHO w s s S KL CASTOR w w s MR

KL ESCORPION w s s S KL CHAJA s w w S

KL GAVILAN s w s MR KL TAURO w s s S

P.PUNTAL w w w R ONIX w s s MR

S NOGAL w w w R PGAUCHO w s s MR

"Vernalization gene analysis conducted by Dr. Marcelo Helguera, INTA, Marcos Juarez ** R= Resistant, MR= Moderately resistant and S= Susceptible

and biological changes occurring in the soil system are making it a better productive system in a continuous manner. The higher water holding capacity and accumulated soil fertility over time have allowed farmers' to use agronomic practices that achieve ever increasing yields in all crops. Higher crop yields mean more stubble for ground cover leading to the next cycle of improvements of the system.

In the highly productive systems in the humid regions, lodging associated with plant height and weak straw is a problem. In parts of Southern Argentina inter seeding of soybeans between the standing rows of wheat before its harvest is being evaluated (Abbate pers comm.). This gives the farmers an advantage to seed soybeans almost a month in advance resulting in higher yields and economic benefits. Under this system of inter seeding, varieties with weaker straw strength are unacceptable. Given the wide variability in germplasm for plant height, selection of semi dwarf varieties is a general norm. Although semi-dwarf varieties suffer a serious reduction in height and biomass under drier conditions, this situation is less likely to occur on well managed zero tillage farms. In general weaker straw strength of the regional germplasm is associated with selection for low input environments. As a result of this negative trait the locally bred varieties are losing ground to high yielding French germplasm with stronger straw strength.

As the productive systems improve with zero tillage and the economic criteria favors to maintain its dynamics, stronger straw strength in high yielding varieties will become an important selection asset.

Resistance to Diseases

Frequent rainfall and moderate temperature during the winter and early spring produce a highly predisposing environment for several disease pathogens that attack wheat in the Southern Cone region (Antonelli, 1983; Kohli, 1985). However, only a few of them, especially of fungal origin, develop in a sufficient manner or have wide distribution to constraint wheat production seriously. A few of these acquire more significance under conservation agriculture due to little o no removal of the stubble from the soil surface or when the correct rotation scheme is not followed. Relatively slow decomposition of the wheat stubble in the major wheat growing region allows it to be colonized by facultative parasites which constitute as a bridge for the crop the following year (Annone and Kohli, 1996).

Wheat-soybean sequence of crops every year in the acid soils of Brazil led to serious infection by Take All root disease caused by Gaeunmannomyces graminis var. tritici, earlier known as Ophiobolus graminis (Reis, 1990). Although Take All infection was observed to increase by incorrect liming practices, it was wheat followed by wheat that really accentuated the seriousness of the disease under Zero Tillage system (Table 3). Incorporation of black oats and horse radish in the rotation system to replace wheat during the one or two winter seasons, not only improved the soybean yields but also the wheat yield significantly.

Table 3. Effect of tillage system and liming on the spread of Take All disease of wheat in Brazil (Reis, 1990)

Tillage system Take All incidence (%)

Control Limed Average

Zero tillage 10.2 36 23.1 a*

Conventional Tillage 7.6 6.4 7.0 b

Average 8.9 B 21.2 A

* Averages followed by different letters indicate significant statistical differences (0.05P).

Table 4. Stubble quantity managed under different tillage systems and its relation to the inoculum of B. sorokinianaand D. tritici-repentis

in Brazil (Modified from Reis et al.., 1992)

Treatment Conservation tillage Conventional tillage

Zero Minimum Disc plough Mould Board plough

Wheat residue (g/m2) 271.1 170.8 36.1 12.4

Percent 100 63 13 6

B. sorokiniana (spores/m2) 159 x106 9.99x105 2.11X105 7.27x104

D. tritici- repentis (pseudotecia/m2) 11653 7310 1548 516

Foliar and spike diseases, caused by various species of Alternaria , Fusarium, Helminthosporium and Septoria, are all related with the wheat stubble left on the soil surface and have become more severe under zero tillage system. Of these, tan spot caused by Pyrenophora tritici-repentis (Died.) Drechs. (teliomorph of Drechslera tritici-repentis (Died.) Shoem. has become of worldwide importance and is associated with the increase in the conservation agriculture (Gilchrist et al., 1984; Hosford, 1982; Kohli et al., 1992, Rees and Platz, 1992). Early in the adoption of zero tillage in Brazil, Reis and colleagues (1992) measured the number of Pyrenophora and Drechslera spores under different tillage systems to demonstrate the need for correct crop rotation as a key to the success of conservation agriculture (Table 4). In this case again, the addition of black oats in the rotation system has become critical to the continued wheat production in the humid parts of the region.

In addition to tan spot the frequency of the epidemics caused by Fusarium head blight, FHB, (Fusarium graminearum) under zero tillage has also increased significantly. Given that maize is one of the favored crops to add extra stubble in the rotation system, it has also become a major source of FHB inoculum to infect wheat (Table 5). Galich et al.. (1994) demonstrated the impact of maize crop on the FHB infection; indicating thereby a strong need evaluate the rotation system practiced to generate high quantity of stubble. In spite of its economic importance, leaf rust disease caused by Puccinia recondita, does not modify its infection pattern based on the tillage system.

Table 5. Disease index and severity of Fusarium on wheat based on tillage system and preceding crop (Galich et al., 1994)

Preceding crop Severity (%) Disease index

Zero tillage Minimum tillage Zero tillage Minimum tillage

Maize 47.0 33.6** 46.3 31.0**

Soybean 38.3 34.8* 37.1 31.8**

*: Statistically significant at 0.05 P and **: Statistically significant at 0.01 P.

While there is significant variation in the germplasm for resistance to individual diseases, most of the high yielding varieties lack a combination of resistance to diseases prevalent each year. The most difficult of the combination is to foliar blights such as septoria leaf blight and tan spot and FHB in the southern humid regions and that of spot blotch, Alternaria leaf blight and FHB in the northern humid regions. In a series of experiments conducted in Uruguay to understand the tillage x germplasm interaction, its most important component was defined by fungicide application to control the diseases (Table 6).

The climatic conditions of the years were variable enough (data not shown here) to impact the disease development significantly, which in turn effected the cultivar performance and its interaction with the tillage system. In a combined analysis over the years, the cultivar x fungicide interaction remained strongly significant over the years (P 0.004) while cultivar x tillage interaction remained significant at a lower level (P 0.063).

Table 6. Statistical analysis (Pr> F) in Type 3 tests of fixed effects of tillage interactions

Effects 2001 2002 2003

Tillage 0.366 0.08 0.869

Fungicide <.0001 <.0001 0.002

Tillage x Fungicide 0.004 0.229 0.979

Cultivar <.0001 <.0001 <.0001

Tillage x Cultivar 0.075 0.005 0.414

Fungicide x Cultivar 0.0005 0.003 0.002

Tillage x Fungicide x Cultivar 0.66 0.382 0.77

Synchronous Heading, Rapid Grain Filling and Quick Finish

The Southern Cone wheat germplasm, in general, lacks synchronous heading. In extreme cases the heading period in some regional cultivars can extend over weeks. While non synchronous heading escapes severe damage caused by spike diseases or frost, increased flower abortion and grain filling under high temperature conditions result in lower grain yield and physical quality characteristics. The rapid adoption of high yielding French germplasm in Argentina is not only due to its stronger straw strength but also to synchronous heading which allows uniform grain development and better spike fertility.

Baethgen (1998) reported the grain filling period to be one of the two critical periods in grain yield formation in the region. He also identified minimum temperature and solar radiation as two fundamental factors affecting this period. However, there are large parts of the region affected by high temperatures during the grain filling period. In addition wheat cultivation has expanded to newer and warmer regions in the lowlands of Bolivia, central Brazil and Paraguay.

In order to determine the variability for grain filling in Northern Paraguay, 1000 grain weight (TKW) at 25 and 35 days after heading was measured as a percent of TKW at the harvest time. Compared to Estanzuela Cardenal (Cordillera 3 in Paraguay) of Baethgen study, a rapid grain filling variety, and other local varieties which filled almost 80 and 90 percent of their weight at 35 days, several others filled the grain almost 100 percent, Fig. 4. Such a variation in grain filling characteristic under high temperature conditions is of key importance to be exploited especially when a second crop of soybean needs to be seeded on the same land.

Besides rapid grain filling, a quick finish without shattering is another useful character to allow an earlier seeding of the soybean crop. A quick finishing variety, such as PROINTA Puntal, can be harvested almost a week or more earlier than other varieties seeded on the same date. Data from official trials conducted at INTA Balcarce, Argentina, where lower temperatures generally favor longer grain filling period, PROINTA Puntal matured on an average 4.9 days before the average of the trial over a five year period, Fig. 5, (Abbate unpublished). Such quick finish did not seem to hurt its average yield over the years (5704 kg/ha), which was 451 kg/ha over the average of the trial. However, a comparison of P. Puntal with Jagger and Baguette 10, another popular variety of French origin, conducted at INTA Marcos Juarez did not demonstrate any significant difference in the rate of grain filling between them (Fraschina unpublished).

Lack of Late Tillers

Significant differences among the varieties for their susceptibility to producing late tillers have been observed. The production of late tillers which affects the normal harvest is caused by precipitation after a prolonged period of drought, freezing damage or by lodging of a crop. At present such a condition is being dealt by the farmers through application of desiccants. Given the genetic variability available for this character, its inclusion in the desirable traits to be selected is becoming important.

Higher Yield Potential

Ferrari (1998) conducted long term yield trials on wheat/soybean-maize and wheat/soybean rotation schemes on two types of soils to report a 3-8 percent decrease in grain yield under zero tillage when compared to conventional tillage. It raised serious questions regarding specific needs to identify or develop high yielding germplasm adapted to zero tillage conditions considering a genotype x tillage interaction shown by Hall and Cholick (1989). As a result,

Figure 4. Relative grain weight of selected wheat varieties at 25 days and 35 days after heading compared to it at harvest time. Yjovy, Paraguay, 2003-04.

Figure 5. Days between heading and maturity of PROINTA Puntal wheat variety compared to the trial average at INTA Balcarce, Argentina

Kohli et al. (1999) analyzed a large number of agronomic characteristics to propose an ideotype that will adapt better under zero tillage conditions. Trials conducted in Uruguay during 2001-03 confirmed the Cultivar x Tillage interaction but also observed it to be seriously effected by the level of fertilization and disease control, Fig. 6, (unpublished data).

Malbran et al. (2008a) studied similar interaction of facultative wheat varieties under very dry conditions in Argentina (Fig 7). In their study the precipitation during the critical period, when grain yield and quality is defined, was 54 percent lower than the historical average. In addition, high temperature during this period accentuated the evapo-transpiration and demand for more water by the crop. Such conditions allowed visualizing the effects of the tillage systems on the crop development, grain yield and quality parameters. Contrary to the earlier results, grain yield of all varieties under test improved under the zero tillage. Some advanced lines (LACL 04 and 09) performed

[□Conventional B Zero tillage

■o6000 ——~—pm—^—i———-m--

4000 ; S , li:;-B-LiS-Ljl-bM , -' I -: " I

Figure 6. Grain yield of ten cultivars under two tillage systems, La Estanzuela, Uruguay

Tillage

Figure 7. Grain yield of six facultative wheats under two tillage systems in Argentina. (modified from Malbran et al., 2007)

relatively better under conventional tillage conditions while Buck Guapo variety produced much higher yield under the zero tillage. Quality parameters measured in this study, such as percent protein and gluten, test weight and thousand kernel weight, suffered a serious loss under the zero tillage conditions due to lower nitrogen availability in the trial. A similar study on the spring wheats failed to demonstrate similar interactions. (Malbran et al., 2008b).

Another recent study compared grain yield of several wheat advanced lines at an experiment station (INTA Marcos Juarez, MsJz,) and a nearby farmer's field at Corral de Bustos (CB) Figs. 8 a, b, c, d. MsJz adopted the zero tillage in the year 2000 while CB field had adopted the system more than a decade earlier. In the year 2000, higher yields obtained at MsJz are indicative of germplasm adaptation to conventional tillage. In the year 2007, although the grain yield increased at both locations, the facultative wheats still perform relatively better at MsJz (Fig 8b) indicating that varieties specific to zero tillage are still not developed (high incidence of the FHB). While spring wheats yield similar at both locations, there are significant differences among the lines selected at each location (Fig 8d). The only plausible explanation can be the lack of stubble cover at MsJz compared to CB trials, which not only points to a strong influence of the stubble on the selection of varieties but also shows wider germplasm variability for grain yield in the spring wheat germplasm. A correlation analysis between these two locations over the years (not shown here) demonstrates that, four out seven years, they fall in different groups indicating thereby a strong year x cultivar x management interaction observed in Uruguay.

Fig. 8a. 2000 Facultative

Fig. 8c. 2000 Spring

Fig. 8d. 2007 Spring

Figure 8. Grain yield of wheat advanced lines in two environments differing in stubble quantity on the soil in the year 2000 and 2007

In general, Argentine farmers have an impression that early seeding of facultative wheats not only allows good initial stand helped by higher soil humidity under zero tillage but also results in higher grain yield. However, in a recent study, Fraschina et al. (2008) found no difference between the grain yield potential of the facultative and spring wheat varieties. The only significant difference observed during one year was due to lower nutrient use efficiency caused by winter drought and late rains that effected spring wheats more than the facultative wheats.

The results discussed so far demonstrate that any Cultivar x Tillage interaction observed in a study depends on multiple factors including crop rotation followed, stubble quantity and quality, fertilization, frost injury, disease incidence and the environmental conditions of the year etc. As the development of newer germplasm under zero tillage conditions receives more attention and becomes successful, a significant increase in the grain yield is expected to follow.

Conclusions

Adoption of conservation tillage practices, especially zero tillage, in the Southern Cone countries has not only reduced erosion related soil losses drastically but also increased the productivity and profitability of wheat/soybean-maize or wheat/soybean-maize-soybean rotation schemes. Over the years wheat yields under zero tillage have increased benefiting from higher water accumulation and soil fertility caused by better stubble management. Although some Tillage x Cultivar interactions have been observed in the dryland areas, they are not always clear and/or significant. Such interactions are accentuated by the amount of stubble, nutrient availability and the environmental conditions of the year which in turn impact the disease incidence and severity.

In order to improve adaptation of wheat germplasm to zero tillage, selective exploitation of genetic variability in some agronomic characters such as crop cycle, early stand establishment, tillering capacity, frost and disease resistance and grain yield is seen essential. The specific combination of these traits required to develop a variety may differ from one geographical region to another depending on its climatic conditions and the crop rotations followed. Yet, the development of zero tillage specific germplasm will not only help achieve ever increasing yields but also guarantee the sustainability of production systems over a long period of time.

Acknowedements

We thank Dr. Pablo Abbate of INTA Balcarce for sharing some of his unpublished data with us. References

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Challenges and Prospects to Realize Diversified Agriculture in the Tropics: The Brazilian Savannah Case

Carlos R. Spehar

Faculdade de Agronomía e Medicina Veterinaria, Instituto Central de Ciencias Ala Sul, C. Postal 4.508 Brasilia, DF, Brasil CEP 70.910-970 (Email: spehar@unb.br)

In view of predicted world population, the pressure over natural environments shall increase considerably. Induced changes in climate, causing weather fluctuations, compound to affect crop performance by drought or excess rain when they are not needed. Additionally, more demand on agricultural products requires high amounts of fertilizers, forcing prices to move upwards. Combination of these factors and their interface are serious threats to agriculture and to mankind. The Brazilian Savannah development has been marked by key events to face intrinsic and extraneous challenges, leading to efficient production. The large-scale occupation, intensified in the 1960's by beef cattle ranchers, was marked by vicious clearance of exceedingly diverse vegetation and disregard to the environment. Great advances on research, especially crop breeding have revolutionized this scenario, turning the savannah into a major food and raw material producer. Prevailing cropping systems, however, have based mostly on soybean and maize, causing income reduction, due to bad soil management and pest and disease problems. These have forced changes of which the most recent comprise the use of zero-till, associated with crop diversification. The former has picked up quite rapidly, while there is a slow move towards introducing innovative crops for soil protection and income source. Considerations about diversified and balanced agro-systems are presented, indicating directions for participatory research and development. The successful experiences and respective outcome serve as template, guiding initiatives in similar, potentially developing, world-wide areas.

Key words: breeding, diversification, innovative crops, zero-till, participatory research.

Many tropical regions of the world have not realized the potential for environmentally balanced efficient production. The Brazilian Savannah, as an example of can be done, had incipient agriculture until the 1960's, despite covering a large cultivable territory all year round. Mostly subsistence activities were secluded into patches of naturally fertile soils in midst of the Cerrado, the local name for savannah. Technological approaches to land use had been extended from traditional areas in Brazil (Spehar, 2008).

Commodity cycles in the traditional areas were confined to former Atlantic Rain Forest, at the expense of devastating exuberant flora and fauna. Possessing reasonably fertile soils, by requiring little input soon after land clearing, they could be exploited for a long period, before replenishing nutrients. Farmers had a chance to capitalize, although were not aware that soils would be depleted, either by the exported end product or poor management (Spehar, 1998; 2008). Such agricultural systems were not sustainable.

In view of this, the savannah land of Brazil had a negligible contribution, with its unfertile soils (Ferralsol group) bearing little production capacity in their natural state (Goedert, 1986). The main activities were restricted to beef cattle ranching, wood for fuel and charcoal, subsistence staples, and native fruits production on extractive basis.

Only a sparse population was found in its domain, originated from pioneer beef cattle ranchers' settlement. No considerable trading, having impact on the country's economy was registered and production was inefficient, requiring large areas. The ratio cow/area was very low, around 5.0. Long distances, associated with lack of technology and understanding on how to manage environmental attributes, were major setbacks (Spehar, 1998).

Pioneer research had identified, as early as 1950's, the need of lime and phosphate to amend savannah soils (Harrington & Sorenson, 2006). These were starting points for strategic management, triggering the changes to the Cerrado scenery.

At that time, technology, however, was not fully available, although few experiments with grain crops were conducted in the savannah core. These actions, expressing the concern about food supply to the inhabitants of Brasilia - the newly built capital, yielded encouraging results to further action. The pioneer initiatives, demonstrating responsiveness of crops, once soils were improved, inspired public policies for research and development, culminating with the creation of institutes in the early 1970's (Spehar, 2008).

The Key to Development

The savannah lands of Brazil, although possessing setbacks were managed long before the modern conquest (Spehar, 1998). Beef cattle ranching activity relied on scheduled burning for the re-growth of native grasses. At this phase their forage is most utilized by livestock, yielding economical results only because of its reduced production cost. There was little prosperity and the living conditions of local populations were very modest, based on mining scarce nutrients from soils (Spehar, 2006).

There were favourable aspects that long attracted the attention of producers from other parts of Brazil. These were i) defined rainy season and ii) vast flat areas, easy to mechanize and suitable for annual crops. Modern settlement, however, needed the support of knowledge and technology to incorporate entrepreneurial agriculture. Even when these became available, it was difficult for common farmers to undertake the conquest of savannahs. The main factors reducing the prospect of rural populations were isolation from the rest of the country, lack of education and training to overcome soil problems and to profit from major investments opportunities (Spehar, 2008). So, this huge area, covering one fourth of the country, remained neglected for a long time (Spehar, 1998).

It must be emphasized that, along time, naturally fertile land in Brazil was restricted and over farmed in the traditional zone. Natural resource exploitation model, marking the tradition on agriculture and rural development, was a dead end in itself (Navarro, 2001).

A combination of forces drove the Cerrado and other parts of the country into a new paradigm of development, shifting from extensive ranching into intensive, modern and profitable agriculture. Incorporation of technologies, culminating with no-till and crop diversification, is discussed, giving examples and insights useful in similar conditions.

Natural Trends and the Human Factor

The success in Brazilian Savannah settlement relied on the support for research and development. Without sound information on soil amendment, constructing fertility, the inertia would still prevail. Even though the necessary knowledge to make use of savannah land was being generated, it needed on-farm testing and application (Spehar, 2008).

The actions of research, including crop adaptation, soil and plant management and protection, the ones on development and extension have been associated with effective entrepreneurial attitude of pioneer farmers. The emptiness was gradually filled by settlement of medium to large farm holds, which brought expertise and capacity from the traditional zone of agriculture in Brazil. Their associations, with the inclusion of family farmers, have facilitated technical assistance with improved efficiency (Spehar, 2008).

Concomitant to the settlements, acquisition of technology was strategic. Embrapa (the Brazilian Corporation for Agricultural Research and Development), at the national level, in addition to the state institutes, played a key role. So did demonstrations and validations, while preparing farmers to launching commercial production. The organized extension service, with similar functioning structure, was equally important (Spehar, 2008).

Improved agricultural colleges, associated with research, development and extension, acting together with farmers' participation, was paramount to assure best practices accessibility, leading to biological and economically efficient production (Spehar, 2006).

Permanent search for appropriate technology has resulted in creative solutions being added to the existing frame. Absence of soil movement, associated with protective crops in diversified systems has been the most recent approach. It has been accessible to the range of farmers: from family farms up to large-scale homesteads. As a result, all sectors related to agriculture, have benefited from the process of settling the savannah (Spehar, 2006).

The output has caused positive impact on Brazil's economy, turning the country into a major food supplier, diminishing national famine threat. Before this accomplishment, large quantities of food and agricultural raw material were imported, originating huge deficit in the balance of trade. Considerable decrease in prices of agricultural goods at the consumer level has been the consequence of applied technology. The resulting food, fibber, wood and more recently agro-fuel productions, besides supplying the country's demand, have attracted the international commodity market (Spehar, 2006).

The national development plan, supporting the Brazilian capital move to the hinterland, had relevant effect on the changes. The need to overcome major limitations and the adjustments to it are pointed out, aiming at realized

improvement at the farm. Even though Brazil has reached apparent stability, by the help of Cerrado's conquest, there are set backs in need to be addressed, one of them is lack of diversified production systems.

Land Incorporation, Agricultural Evolution and Threats

The old model of soil exploitation, related to land tenure concentration, aggravated the state of the country's economy. Available land was in the hands of few estate owners, where extensive, sole-crop agriculture compensated for reduced efficiency. As a consequence, small family holds, located in southern Brazil, originated from foreign immigrants, became limited in their perspective for future generations and. With population increase, farmers were forced to search for new areas (Spehar, 2008).

These family farm establishments were the place where skills developed, in addition to the aspirations already maintained by the immigration spirit. At the same time, soybeans became an important cash crop. Its prices in the international market were attractive, with advantages added by subsidies, creating conditions for expansion. Motivated, farmers soon mastered technology for soil improvement. The big jump at this phase was the introduction of high performance soybean genotypes from Southern USA into Southern region (Spehar, 1994). The two areas are located at the same latitude, even though in different hemispheres.

Agricultural advances in the Cerrado have been a result of acquired technology and respective application in the farm. It amplified the prospect for reclaiming and improving soils, turning them agriculturally viable (Spehar, 1998). Extension service and education were added and complemented by strategic public policies, incorporating savannah land into production. Key research advances shall be discussed further in the paper.

The initial efforts, based on the understanding of environment and soil functionality, were to adapt major staple and commodity crops to these conditioners; and to define soil and plant management for competitive yields. Socioeconomic studies, to understand the local existing populations and their production scheme were carried simultaneously (Spehar, 1998). In addition, farming conditions and farmers' skills were improved, with the prospect of social organization in the new environment.

On the infrastructure side, the access to new capital, placed in the core of Cerrado, was made possible by new roads, connecting the most distant regions in country. The aim of these communication infrastructures was to integrate the vast territory into the nation and to facilitate the flow of inputs and agricultural products.

Additional factors such as, low prices of land, incentives for clearing virgin savannah, and facilities for storage stimulated farmers to move from southern Brazil to the agriculture frontier. Road transportation, however, was economically viable at that time, when crude oil was abundant at low prices. Efficient energetic solutions for economical exploitation have led into agro-fuel. In addition, applied technology, increasing average yields of main commodities is needed to compensate shipment costs (Table 1). Inter-modal transportation is under construction, to diminish cost factor in most distant areas (Spehar, 2008).

Table 1. Yield evolution (t ha-1) for major crops, from 1975 to 2005, compared to the potential identified by research

Crop1 1975 Average Yield 1993 2005 Increase Rate (1975-2005) Potential Yield2

Soybean 1,32 2,20 2,81 113 4.5

Maize 1,57 2,70 4,36 177 10,5

Upland Rice 1,03 1,20 2,32 125 3,5

Phaseolus Beans 0,48 0,71 1,83 281 3,0

Wheat 2,80 3,95 5,23 87 7,0

Cotton 1,60 2,63 3,64 127 4,5

Coffee 0,82 1,33 2,35 187 3,5

Adapted from Spehar, 2006.1rain fed crops, except wheat; 2average research yields.

Integrated transportation associated with the improvement of seaport and storage capacity and hydroelectric power availability have consolidated development. Soybean price and respective production cost, for different regions, however, illustrate the need to rationalize infrastructure. If the national average yield of 2.7 t ha-1 is considered, farmers in most distant states may not pay the production cost. (Table 2). Efficiency increase, although necessary, demands farmers' training to achieve highest output/input ratio, reducing the gap between potential and obtained yields.

Table 2. Distance effect on income for major soybean producing States

State Distance1 Received Price2 Production Cost3 Net Income4

(Km) (US $ ha-1)

Rio G. do Sul 500 613 545 68

Paraná 500 613 545 68

Sao Paulo 500 613 545 68

Minas Gerais 700 587 545 43

Mato Grossoa 1,200 555 570 -15

Mato Grossob 1,800 525 550 -25

Goiás 1,200 555 570 -15

Bahia 1,000 565 570 -5

Tocantins 1,200 555 570 -15

1Average distance of production areas to port or industry; 2Average price in 2006; 3Regional average yield = 2.7 t ha-1; 4Net income = received price - production cost; Ssouthern; Nnorthern.

Adding to efficiency, the use of ecological solutions, diminishing demand for high energy requiring input and reducing CO2 emissions, has placed the Cerrado into a reference for tropical agriculture. This is the case of no-till, by suppressing soil movement, a new paradigm for advanced agriculture (Spehar, 2006). The change from raw material supplier into transformed products, with appropriate incentive, has attracted industry to its domain, adding value to raw material (Spehar, 2006). Major achievements need to be implemented, by encompassing crop diversification with associated efficiency, leading to clean agriculture to supply food demand (Spehar, 2005). Moreover, production systems should consider the induced climatic changes, with direct impact on agriculture. These require strategic partnerships to adjust production systems in the whole planet (Spehar, 2008).

Agricultural Potential and Development

The Brazilian savannah was unknown in the world and over shaded by the Amazon rain forest. Its importance for agriculture is higher than the plains of North America, Europe, Argentina and Australia (Spehar, 2006). The common points with the even larger African Savannahs are the poorly fertile soils, although being best supplied by water.

Savannah realms dominate the central part of Brazilian highlands, being influenced and affecting other major eco-physiographic regions such as Amazon Rain Forest, semi-arid Caatinga, Atlantic Rain Forest and Pantanal (Spehar, 2006). They cover huge catchments, being the origin of many rivers of major South American basins. Agricultural activities in the domains should be equitable and environmentally balanced, for long-term, agro-ecological exploitation (Spehar & Landers, 1997).

Technologies for plant and soil management, and the use of economical rates of lime, gypsum, phosphate, potassium, nitrogen and micronutrients, have changed the scenario (Goedert, 1986). Adapting crops and livestock to the environment and respective husbandry have been associated to soil amendment (Spehar, 1994). The technological outcome yielded competitive systems, to be validated in the territory, allowing marginal areas to develop.

There are important factors to depict from this unique experience. These are related to research and development focused on major problems, previously identified by survey. Considerations on the weight of environment components have been necessary to acquire technology for exploitation at economical levels (Spehar, 2006).

Resource characteristics, such as the climatic influences, the soil types, main vegetation features and composition, its fauna and mineral deposits are the key to utilize and manage them suitably. The association of agronomists, biologists and ecologists has been the up-todate approach directed at the agro-eco-system, respecting the natural forces conditioning this unique biologically rich biome (Spehar, 2006).

Changes Leading into Modern Production

Outstanding performance on grain, fibber, and fruit crops marks the participation of savannahs in the national production (Spehar, 2006). Considerable contribution is being achieved by the use of only a small fraction of the total arable land. If all crops, including pasture, are considered, quite a large proportion (about 40 %) of the savannahs has been occupied (Spehar, 2008).

Table 3. Physical and chemical analysis of a typical savannah Ferralsol

Area Physical Chemical

Sand Silt Cay oMT pH A Ca+Mg P K -g dm-3 --- cmol c+ kg-1 --— mg dm-3 -

Virgin 340 190 450 2.0 4.7 1.9 0.4 0.9 16

Amended2 - - - - 5.6 0.0 3.4 8.0 50

1- Organic Matter; 2 - Addition of lime, phosphate fertilizer and the FTE micronutrient source, as investment; potassium added annually.

Annual crops and pasture associations of aluminium-tolerant upland rice, combined with brachiaria grass, marked the beginning. The overgrazing for many years, by "mining" scarce nutrients, has led to chemical conditions close to native savannah (Spehar, 1998). The early erratic experience opened the way for zero-till, associated with crop-livestock systems. Comparison of virgin to improved soil (Table 3), illustrates the extent of changes in fertility needed to prepare for commercial production. In summary, 4 t lime and 240 kg P2O5 ha-1 are used in raclamation. Most important is to master what and when to replenish on the basis ox expected yield. Organic matter (OM is reasonably high in most virgin areas and extensive experimentation data illustrate its value in cation exchange capacity (CEC), water retention and soil favourable physical properties (Silva et al., 1994).

Thus, degraded pastureland can be reverted by accommodating annual nutrient demanding crops and pasture, associated with rational beef and milk productions (Spehar, 2006). This ensures a quite spectacular prospect, indicating the savannah is to become the largest area of continuous agriculture in the tropics. Predictions for 2050, based on present figures and improved technology, indicate major gains impacts on the economy (Table 4). Advances are expected on the implementation of already occupied area, where grain crops increase their participation by three fold, while beef production doubles. Other crops will increase their value, like sugar cane and other agro-fuel crops. With added value, the impact on the agribusiness has a projected value of US $ 350 billion dollars (Spehar, 2006). This envisions a consolidated and prosperous Brazilian hinterland, turning farmers independent of government support for education, health, housing and transportation, while their capitalization should reflect positively in the regional infrastructure (Spehar, 2006).

Table 4. Cerrado utilization, production and value: present and future

Utilization Area (ha) Present (2008) Future ( year 2050)

(million) Production Value Production Value

(million) (US$ billion) (million) (US$ billion)

Pasture 60.0 78 AU1 7.8 140 AU 14.6

Grain Crops 15.0 50 t 9.5 160 t 33.6

Other2 33.5 - 3.5 - 20.0

Total 108.5 - 20.8 - 68.2

Adapted from: Spehar (2006). 1AU=Animal Unit, irrespective of development phase and weight; 2vegetables, fruits, cotton, coffee, sugarcane, wood.

In summary, the key research and development outputs that have contributed to these advances are: definition of amendment techniques to overcome soil chemical set backs; improved crops, tolerant to savannah climatic and soil hindrances; crop husbandry for economical production and suitable soil management. More is waiting to develop, using the lessons of experiences and accumulated knowledge, adjusting technology for creative solutions and breaking of paradigm (Spehar, 2008).

Commodity Cropping Advances and Impacts

Upland rice-pasture pioneer cropping was followed by winter cereals. More than 20 years ago, it was demonstrated wheat was adaptable to the savannahs, fetching 5t ha-1 on irrigated areas (Silva et al., 1976; Silva & Andrade, 1983). Genetic improvement was the key for its adaptation. Nutritional hindrances were first identified, inspiring other studies to solve similar problems on major field crops (Spehar, 2006). Irrigated wheat, after continuous variety selection, has reached 8t ha-1. It is the highest yield in the world, considering 120 days of plant cycle, between emergence and maturity. Selected genotypes in the tropics can be tested and adapted for similar areas.

Barley, grown until 10 years ago only subtropical areas of Brazil, has been adapted to the savannahs. Cultivar acquisition, a result of partnership with private enterprises, shows high yields in experimental fields (5 to 6t ha-1) and protein content lower than 12%, within the quality standard required by malt industry. The results with summer and winter cereals are a demonstration of advances for their cultivation in the tropics (Embrapa, 2005).

Identification of late flowering soybeans, in low latitudes, has been the major factor for savannah development. The incorporation of long juvenile trait, inductive of late flowering, allowed plant grow for combine harvest, with higher yields than traditional cultivars, extending soybeans into tropical and equatorial regions (Spehar, 1995; Spehar; & Souza, 1999). In addition, savannah soils abide actinomycet fungi, which are antagonistic to nitrogen-fixing bacteria, preventing nodulation. Selected genotypes suffered from N-deficiency due to Streptomyces spp. (Coelho & Drozdowics, 1979). Thus, adaptation of soybeans combined genotypes with tolerant Bradyrhizobium strains.

Selection of early to mid-cycle cultivars has contributed reduce climatic risks and to the opportunity of double cropping and sowing expansion (Embrapa, 2006; Spehar, 1995; Spehar & Souza, 1999). Acquisition of genetically modified (GM) cultivars has reduced pesticide use, with lower production costs and environmental gain. To add value, family farmers have grown organic soybean, by using genotypes with special characteristics, creating alternative for food and trade. Moreover, produce transformation in the property allows adding value on milk, hogging and poultry productions.

Crop improvement by accumulating adaptive genes has been extended to other commodities. In general, it comprises germplasm introduction, characterization, selection, hybridization, progeny evaluation and regional and uniform trials, culminating in the recommendation of hybrids and cultivars. The continuity on this procedure has resulted considerable increase in numbers of superior genotypes, possessing high and stable yields on integrated production systems (Spehar, 2005). New genotype release has been associated with seed production, assuring access to effective input (Spehar, 1994).

The virtual absence of frost and extended rainy season, are favourable conditions creating opportunity for diversified cropping (Spehar, 1998). When irrigation is available, at least three full grain crops per annum are possible. Cropping associations and sequences can be arranged, ensuing production stability. Soybeans and maize monocrops need the synergetic effects of other potential species. Thus, phaseolus beans, wheat, barley, and less exploited grains and fibbers are gradually fitting in (Spehar, 2006).

Among the summer cereals, maize has shown considerable yield gain. Coming from the long tradition in agriculture, this crop has been incorporated into the food habits and raw material for livestock feeding. Its importance in the savannah land has grown, closely connected with soybean expansion. This crop has been a measure of technology adoption, where yields vary from less than 1t ha-1 to outstanding performance (>10t ha-1). Hybrids and open-pollinated varieties have created conditions for its economical cultivation to suit different farming conditions, responding for 35% maize production.

Contrasting with the best yielding hybrids, requiring high input, including seed cost, there are the open pollinated varieties (Machado & Fernandes, 2001). These are of low cost, useful to amplify double cropping under certain risk conditions, to reduce diseases and pests, to increase offer, improving food and feed security.

Rice cultivation in the savannah has declined, since soybeans have taken its place in savannah agriculture. The reason behind reduced area has to do with susceptibility to drought and diseases and the low grain quality, due to weather instability. Selection of dry land rice varieties, aimed at high grain quality and disease resistance, has created conditions for its return to the savannahs at a high technological standard. In rainier areas, the end-product is comparable to paddy rice from other regions in the country (Embrapa. 2007).

Sunflower is a crop showing outstanding performance in the savannah soils. Research has consolidated the crop as an alternative for diversification. Sixty-five thousand hectares have been grown in the Brazilian savannahs, or about 80% total. This has been based on crop adaptation to succeed soybeans in double-cropping scheme (Embrapa, 2005).

Cotton has been associated with the local culture since old times. It is a crop that, in certain occasions, became important to the Brazilian economy. Before the big rush to the savannahs, there were early settlements, established in naturally fertile patches. In these, cotton predominated at family farm holds (Spehar, 2006). Decline in prices and increasing pest problems due to its sole cultivation were major setbacks. Technology adjustments to savannah soils resulted in modern cotton production, or 74% of total. Its insertion into cropping systems has been

a result of variety acquisition, definition of nutritional needs and proper plant husbandry. Its rotation with other annual and perennial crops has improved management, diminishing pest and disease problems (Embrapa, 2005).

Kenaf, industrial fibber plant, has shown as potential crop for the savannahs, after being introduced in the 1990s. The extraordinary adaptability has been demonstrated in cropping systems, in succession to main summer crops (Spehar, 2008). Increasing demand for its fibber make it prone to be cultivated in large areas, by using available technology for cultivar, seed production, husbandry, soil fertilization, harvest and fibber extraction.

Innovation in Savannah Cropping Systems

With increasing demand for healthy and innovative food, agro fuel and other raw material, some under-explored crops have the opportunity in the production systems. Crop diversification on commercial basis has just been touched. Non conventional sowing such as relay and mixed species is being under study, although suffering from limited resources. This area deserves much attention and, unfortunately has received little. Only a few initiatives have been put into action, generating interesting pioneer results (Spehar, 2008).

By studying the performance of synergistic plants, such as pigeon pea (Cajanus cajan), kenaf (Hibiscus cannabinus), grain amaranth (Amaranthus spp), quinoa (Chenopodium quinoa) and other named innovative crops, new advances can be achieved to enhance production (Rocha, 2008). Examples are presented to illustrate possibilities.

The Grain Amaranth and Quinoa Example

Quinoa (Chenopodium quinoa) and amaranth (Amaranthus caudatus, A. cruentus and A. hypochondriacus) are grain species introduced and adapted to savannah cultivation. They have some common characteristics, such as high quantity and quality protein, and absence of gluten. These attributes make them useful to special diets due to protein quality, low cholesterol food (Spehar, 2007a; 2007b). Even though belonging to distinct botanical families, i.e., Chenopodiaceae and Amaranthaceae, their general composition in carbohydrates, fat and protein is proportionally close to the cereals. They are excellent source of iron, calcium and manganese, surpassing the other grains. That is why, after being neglected by the scale agriculture of the world and kept secluded to the regions of their origin, they are being re-discovered in modern times. Many other crops will follow.

These two grains, also known as pseudo-cereals, can be utilised as feed and in ration for domestic animals. In swine and poultry, they are more advantageous than maize and soybeans, for being naturally balanced in essential amino-acids (Spehar, 2007a; 2007b). This quality gives them also the chance to participate in human diets, improving the standards of food quality in the world. Their adaptability into the savannah environments, gives the opportunity for a better prospect of food security in developing countries.

Since there was virtually no work with these crops in Brazil, until the late 1980's, an ambitious programme was initiated. After germplasm introduction and selection, pioneer cultivars have been acquired and a technological package has become available for commercial production. The best performing progenies were included in sowing date and plant population trials. Foliar analyses have indicated their needs in nutrients, defining maintenance fertilization. Harvest techniques and post-harvest handling have culminated with a technological package for commercial production (Spehar, 2007a; 2007b).

The average yield of pioneer cultivars is superior to 2.0 t ha-1, possessing market-sought characters. The great opportunity of introducing them in double-cropping, following maize, soybean or phaseolus beans is the low cost in seed increase and other input., while fetching attractive price in the market (Table 5). As production increases, reductions in price are expected, even though profitable and advantageous to the system (Spehar, 2003).

The quinoa and grain amaranth cases have become reference to other pioneer initiatives aiming at introduction of diversity into cropping systems. The highly diversified native vegetation inspires the attempt to create new paramount production chains aiming at a long term prospect (Spehar, 2006).

Similar small grain plant species can be combined for cocktail relay sowing, giving opportunity fill gaps during the rainy season. Considering most savannah areas of the world have limited rain fall, their sowing over the maturing soybean maize, phaseolus beans and other summer crops allows best moisture use.

Carlos R. Spehar — Challenges & Prospects to Realize Diversified Agriculture

Table 5. Quinoa and maize production cost, income and net profit1

Item Unit Quantity Price

Maize Quinoa Maize Quinoa

Mineral Oil l 0.50 - 2.25 -

Desiccant l 3.00 - 30.15 -

Seed kg 20.0 15.0 141.00 15.00

Seed Treatment kg 0.30 - 18.00 -

Fertilizer 8-20-20 kg 500.00 400.00 255.00 204.00

Insecticide kg 0.03 - 5.50 -

Herbicide 1 l 0.50 0.50 38.00 38.00

Herbicide 2 l 3.00 - 25.40 -

N Band Application 1 kg 160.00 80.00 49.00 24.50

N Band Application 2 kg 160.00 60.00 62.90 23.60

Weed Management - - - 90.00

Indirect Cost R$ 474.78 474.78

Total Cost R$ 1,101.98 824.88

Yield T ha-1 7.20 2.00

Income R$ 1,440.00 2,000.00

Net Profit R$ 338.02 1,175.12

1 US $1.00=R $2.10; values and exchange rates for 2006.

The Challenge for Diversification

Production systems, to develop and reach stability levels, have to be harmonized with the natural forces (Spehar, 2008). Agricultural systems that include rotation, association and succession of crops, of unique botanical characteristics, i.e., different genus and families, are a target to be pursued, mainly in the tropics. Suitable combinations contribute to improve the biology of these systems, in addition to food security and the onset of new markets (Spehar & Souza, 1993; Spehar, 2007a; 2007b).

There are great challenges to achieve a diversified and balanced system. Crop improvement relies on the introduction of plants with special characteristics. Thus, drought and acid soil tolerance, efficiency of nutrient and waster use, tolerance to shade and adaptability to unconventional sowing, such as relay, are desirable. These plants should maximize the commercial product (grain, for example), while leaving considerable amounts of residues to protect the soil. They should contribute new products for human and livestock, cycle nutrients and increased income (Ascheri, et al., 2002; Spehar, 2002; Spehar & Santos, 2002; Spehar, 2007a; 2007b). Their inclusion results biological, economical, social and environmental optimization.

Adaptation has been based on progeny selection, followed by trials for cultivar acquisition; definition of cultivation methods, such as sowing dates, plant population, fertilization and sowing methods; identification of uses in domestic culinary and industry; connection of demand with farmers, launching the production chain (Ascheri, et al., 2002; Rivero, 1994; Spehar, 2007a; 2007b; Spehar & Santos, 2002; Spehar et al., 2003, Teixeira et al., 2002). Broadcast by media agents has contributed greatly to initiate demand, by the prospect of improving diets of city dwellers. The combination of interests on innovative crops to improve diversified farming, shall cause positive impact in the production chains.

In the effort to adapt novel crops, high importance is ascribed to genotype selection (Rocha, 2008). These, before recommendation to farmers, are evaluated in different environments, using the respective control (Spehar, 2007a; 2007b).

On the other hand, experimentation based on small plots, is not always replicated in farming areas, aimed at commercial production. In general, these are small seeded plants, with specific soil requirements, for which there is need to define a minimum technological package (Spehar, 1998; Spehar, 2000). By converting limitations into advantages, low-cost, sowing methods can be improved to fit theses crops into existing gaps. Under this prospect there is opportunity for income on competitive basis (Spehar et al., 2003).

On the biological aspect, new diseases and pests have become epidemics, which are promiscuous to the main crops. Among them, there quite a few examples such as: white fly (Bemisia spp.), white mold (Sclerotinea

sclerotiorum) and Pratylenchus brachyurus nematode. On the latter, little is know about novel crops reaction (Inomoto et al., 2007).

Considering sanitary benefits, the research results, for crops whose production chain is still being developed, are indicators of the changes that are to take place in agricultural systems (Spehar, 2007a Spehar, 2007b). In addition to grain amaranth and quinoa, other such crops are being studied, as kenaf (Hibiscus canabinus), sesame (Sesamum indicum), safflower (Carthamus tinctorius), guar (Cyamopsis tetragonolobus) okra, aibika and musk mallow (Abelmoschus spp.), enlarging the prospect for diversity. These species may combine relay and mixed cropping, for maximal yields (Spehar, 2008).

In order to materialize the technologies for diversification, amplifying the range of possibilities, it is necessary to invest in all levels, mainly on communication. The on-farm experimentation, should involve crop and soil management, aiming at the validation of techniques. Comprehensive agronomic coverage should be complemented by adding value and leading to commercial production. These actions should be contemplated by appropriate public policies favouring diversified cropping..

Advantages by the Insertion of Innovating Crops

Synergy to production systems is the first advantage in need to be best understood. Wild sunflower (Thitonia diversifolia), for example, is a mycorrhiza multiplier, favouring the succeeding crops that might be dependant of these soil borne fungi. They form associations with most plants, improving phosphorus uptake efficiency. The plant is perennial and herbaceous, turning its management easy to be done and being useful in weed control (Spehar, 2008). Knowledge on plant performance, in multi-cropping, should take into account interactive these effects. There is a lot to be done, discovering the benefits of associations, sequences and rotations, similar to the natural environments. In native savannah, inhabitants create means for reciprocal survival (Spehar, 2007a).

Many of these newly introduced crops do not multiply soil borne fungi and pests such as nematodes of great impact, especially in sandy soils (Inomoto et al., 2007). The great options turn higher the chances to establish favourable, synergistic and biologically balanced cropping systems.

One relevant point turning feasible the introduction of less exploited crops is the innovation in sowing methods. Even though relay sowing is desirable to improve farmer performance, much information is needed to consolidate the technique (Trecenti, 2005). A major advantage is given by the great multiplication rate, allowing farmers to produce their own seeds. They may also be used as a second choice, when the first option for double cropping does not work. Synergy to the cropping system may become an asset, when market has not yet been initiated. The advantages pointed out here need to be more studied and understood, being demonstrated to the farmers, before diversification takes place.

Addressing Questions

The feasibility of commercial production of agriculture innovating species, taking the examples of grain amaranth and quinoa is still limited. This is partly due to the reduced knowledge about their value to agricultural systems and market (Spehar, 2007a; 2007b). Increasing support for comprehensive projects on research and development, covering genetic improvement, crop husbandry, soil management, trading and uses, is needed, similarly to what has been done with major commodities (Spehar, 2008).

Innovating plants, to be inserted in the world market, need to have a minimum technological package defined, with producers' participation. The outcome should be economically efficient yields, on top of biological balance and better soil management (Spehar, 2008). Experimentation in farmers' fields, involving their direct participation, should be previously defined by competence, leadership and consequent interest in developing these crops, to popularize their use.

In the experimentation, some key factors should be taken into account such as variety acquisition belonging to differentiated maturity groups; spatial arrangement, sowing pattern and dates suitable for each genotype to express best performance by input; and appropriate nutrition to reach these efficient yields (Spehar, 2007a; 2007b). Such work has been carried out in loco, i.e., in agricultural properties, aim at demonstrating the benefits of innovative crops. The value of these actions is based on special events concomitant to experimentation such as field days and technical meetings, to ensue the participation of production chain representatives. Multiplication of events, such as these, is an excellent opportunity for contacts and agreements aiming at market and uses (Spehar, 2008).

The little promotion of crops and their advantages has limited them as options for food and raw material. The farmer does not cultivate them in face of limited knowledge of best techniques and trading; this, in turn depends on consumers, who do not know where to purchase the products (Spehar, 2008). Efforts geared at economical analysis, taking into account projected prices by emerging market, shall encourage adhesion of reluctant producers. Complimentary actions, by broadcasting information among producers and demanding public, aim at establishing new links among the segments, initiating the chain.

Prospect for Diversified Agriculture

Advantages being demonstrated, the need to involve interested people on both ends of the chain comes next. This is why, concomitant to experimentation, initiatives should be taken to develop and promote the innovative products (Spehar, 2008).

Product trading is the major set back to be circumvented by equally strategic pioneer actions. In market formation, up to the point of its production flow, there is need to stimulate involved sectors. The respective chains of innovative species shall evolve from comparative advantages; in traditional species this was realized along dozens or hundreds of years (Spehar, 2008). Given present technological advances, especially on communications, time can be shortened. Thus, it is proposed the use of virtual environment, connecting the links and making the chain, on independent trading. This should help farmers and consumers, but relies on education, training and special public policies to stimulate diversification (Spehar, 2008).

Well defined strategic actions, supported by public policies, on research and development, promotion of cultivation and uses on diversified basis, shall be target. It is expected that, in the years to come, innovative crops become a reality in farmers' fields. Well balanced farming for the tropics relies on these actions leading to clean food, fibber, agro-fuel and other derived products (Spehar, 2006). Needless to say but well enough to remind, the new agriculture, supporting a quickly changing world, should face the mirror of nature. The observations and coexistence of man and other living beings, in close ties of traditional agriculture should be revived in present times, using technology advance.

References

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Spehar, C.R. 2005. Opçoes de cobertura e suas influências em áreas de Cerrado. In Encontro de Plantio Direto no Cerrado, 8. p. 81-86. Tangará da Serra, MT, 2005. Tangará da Serra: APDC.

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Strategies for Developing Rice-Wheat Genotypes for Conservation Agriculture

B. Mishra1 and Ravish Chatrath2

1Sher-E-Kashmir Univ of Agricultural Sciences & Technology, Jammu, India 2Directorate of Wheat Research, Karnal, Haryana, India

Continuous adoption of rice-wheat system with maximum exploitation of natural resources has weakened the resource base. If we continue to exploit the natural resources at the present rate, productivity and sustainability are bound to suffer. Therefore, to achieve sustainable higher productivity efforts must be focused on reversing the trend in natural resource degradation by adopting efficient resource conservation technologies. Development of efficient genotypes for conserving natural resource base is increasingly looked as one of the viable options. The time has come for an integrated rice-wheat research towards development of varieties with efficient input use and complete compatibility with each other. Conservation agriculture aims at application of modern agricultural technologies to improve production while protecting and sustaining the natural resources. Application of CA promotes the concept of optimizing yields and profits while ensuring provision of local and global environmental benefits and services. Acreage under conservation agriculture which is characterized by minimal soil disturbance before seeding and by diverse strategies to increase crop residue retention on the soil surface to insure maximum ground cover over time has dramatically increased in many countries over the past 3 decades. There are now about 28 million ha of zero till seeding in Latin America with the bulk concentrated in the southern cone countries of Brazil, Argentina and Paraguay. Much of this acreage is zero-till with residue retention under rainfed condition.CA in the form of conservation tillage (zero/reduce/bed planting) and incorporation of crop residues have been introduced in the irrigated regions of IGP to reduce the cost of cultivation, saving the resources like water, fertilizers, energy and time, improve the soil health and enhance the system productivity. By 2025, 15 out of 75 million hectare of Asia's flood-irrigated rice crop will experience water shortage. Yet more rice needs to be produced with less and less water to feed the burgeoning population. Rice is an important target for water use reduction because of its relatively large water requirement compared to other crops. This aspect of rice cultivation is undergoing radical changes and technologies are being aggressively developed for more water productive cultivation practices. System of Rice Intensification (SRI), direct seeding under puddled soil, alternate wetting and drying, aerobic rice cultivation are some of these practices. The suitable varieties for different agroclimatic situations should be screened or developed through breeding for SRI, direct seeding, aerobic rice cultivation etc. The available information indicated that where high yielding lowland rice varieties grown under aerobic soil conditions but with supplemental irrigation as a measure to save water have shown severe yield penalty. Achieving high yields under irrigated but aerobic soil conditions require new varieties of aerobic rice that combine the drought resistant characteristics of upland varieties with high yielding characteristics of lowland varieties. The variety so developed should perform well both under aerobic condition as well as under normal irrigated condition, so that chance of getting a good harvest in a good rain fall year is not skipped. Rice variety that has competitive ability to suppress weed growth or which give a reasonably good yield under unweeded conditions should be developed to reduce investment on weeding including herbicide use. So far the development of rice and wheat cultivars were focused on individual crops under good seed bed condition involving more number of tillage operations. The breeding programme should consider system approach to suit the requirement of conservation agriculture. In areas where new resource conservation technologies are gaining popularity, farmers require cultivar adapted to the new practices. For surface seeding and reduced/zero tillage planting, the cultivar should posses faster root development to enable rapid establishment of the crop, thereby getting the seedling past an early and harsh environment and taking the best advantage of available soil moisture. Recently significant genotype x tillage interactions was reported in tests involving diverse genotypes, requiring plant breeders involved in wheat improvement to tailor the genotype to different resource conservation technologies. Varieties that possess faster root growth, and good vigour may present opportunities for increased productivity under reduced tillage condition. Biotechnological interventions in mitigating abiotic stresses are set to play a major role in conservation agriculture. Among abiotic stresses drought, extreme temperatures, and saline soils are the most common stresses that plants encounter. Genetic engineering for developing stress tolerant plants, based on the introgression of genes that are known to be involved in stress response and putative tolerance, might prove to be a faster track towards improving crop varieties for conservation agriculture.

Key words: Rice, Wheat, Genotypes, Conservation agriculture, Input use efficiency

Strategies for Developing Rice-Wheat Genotypes for Conservation Agriculture

The key feature of the Green revolution strategy included the expansion of irrigated area, the introduction of high yielding and input responsive dwarf rice and wheat varieties, and the promotion of fertilizer usage. Other supporting element included the expansion and strengthening of research and extension services, and agriculture support policies.

The combined effect of the increased use of these variables resulted in a substantial increase in food grain production from 55 m tons in 1951 to more than 200 m tons. During the past 30 years, agricultural production has been able to keep pace with population demand for food. This came about through significant area and yield growth. Area growth was a result of new lands being farmed and through increases in cropping intensity, from a single crop to double or even triple crops per year. However, the majority of the farm households have less than 5 ha of land. All farmers use improved varieties of wheat and rice with fertilizer. Mechanization levels are high, especially in the western regions, with resource poor farmers renting farm implements for tilling and harvesting. Animal power is still common in eastern parts of RWCS, but many farmers are moving to contract ploughing with tractors.

The problem associated with rice-wheat systems threatens the sustainability of this vital component of food security in India. The gains from the input intensive agriculture of the green revolution era, with high inputs, high yielding varieties, irrigation and other infrastructural facilities have been largely realized. At the farm level, priority should be given to the quantification of site specific problems. In most parts of India, farmers are responding to the problems of rice-wheat systems themselves by adopting precision farming techniques. Using their own ingenuity, the farmers are beginning to diversify crops through rotation, use alley cropping techniques and reduced tillage operations and increased water use efficiency.

Sustainability of Rice-Wheat System in India

Due to continuous use of the rice-wheat systems in the country, concern about the declining sustainability has been widely expressed (Regmi et al., 2002; Ladha et al., 2000). Decline in the yield on long term experimental plots, stagnating farmer yields, declining productivity growth rates and factor productivity in both farm and research settings and degrading soil and water resources have raised questions about the sustainability of rice-wheat cropping system. Continuous use by farmers of the rice-wheat system has been reported to reduce soil and crop productivity. Analysis of several long-term experiments on rice-wheat indicated a negative average yield (-0.02 t ha-1 yr-1 or 0.5% yr -1) trend of rice (Duxbury et al., 2000).

Although RWCS has been a boon from food security viewpoint, it being an intensive cropping system, is heavily taxing the two most important natural resources soil and water (Prasad and Nagarajan, 2004). Trends of resource fatigue, stagnating yield and little area available for horizontal expansion suggest that rice-wheat production systems of Indo-Gangetic plains may not keep pace with anticipated increase in demand for food driven by population and income growth. On the supply side, natural resource management problem, including the unsustainable exploitation of water and soils, inefficient use of chemical inputs, declining environmental quality and emerging disease and pest problems. On the demand side they are being transformed by market forces and changing consumer demand.

Can New Technologies be an Answer?

The continuous intensive cultivation of rice and wheat for the last three decades has put tremendous pressure on the land. Stagnating yield at levels far below the potential productivity and even yield declines are now occurring in south Asian countries including India. The time has come for an integrated rice-wheat research towards development of technologies and varieties with efficient input use and complete compatibility with each other. Promising technologies to ensure timely sowing and good plant stands, crucial for rice-wheat system productivity and efficiency are needed to be developed and popularized among the farming community of Indo-Gangetic plains. Scientist working with various research and development institutions have developed new tillage and other resource conserving technologies such as surface seeding, zero tillage/reduced tillage, bed planting, mechanical transplanting, laser leveling etc. The development and deployment of resource conserving technologies with farmers in the rice wheat systems have been a major success of research and development institutions (Hobbs et al., 2002).

Promotion of resource conservation technologies in IGP have been underway during early 1990s but it is only in the past 6 to 7 years that the technologies are finding rapid acceptance by the farmers due to availability and affordability of seed cum fertilizer zero till drill by the farmers. Efforts have been made to develop and extend conservation agriculture in IGP (Indian region) through the combined initiatives of several SAUs, ICAR institutes and International institute like CG system, specifically, Rice-Wheat consortium for the Indo-Gangetic plains. Unlike, in the rest of the world, spread of technologies is taking place in the irrigated regions in the IGP where rice-wheat cropping system dominates. CA systems have not yet taken roots in other major agro-ecoregions like, rainfed,

semi-arid tropics, the arid regions or the mountain agro-ecosystems. CA in the form of conservation tillage (zero/ reduce/bed planting) and incorporation of crop residues have been introduced in the irrigated regions of IGP to reduce the cost of cultivation, saving the resources like water, fertilizers, energy and time, improve the soil health and enhance the system productivity.

Importance of Timely Wheat Sowing

The most common practice for establishing rice in the RWCS is puddling before transplanting rice. This results in degraded soil physical properties, particularly for fine textured soils, and subsequently results in degraded soil physical properties and subsequently creates difficulties when it comes to providing a good soil tilth for wheat (Sharma et al., 2002). Delaying wheat sowing (normal to late) resulted in decrease in yield by 15.5, 32.0, 27.6, 32.9 and 26.8 kg/ha/day under NHZ, NWPZ, NEPZ, CZ and PZ, respectively for timely sown varieties. The corresponding yield loss was 7.6, 18.5, 17.7, 17.0 and 15.5 per cent (Tripathi et al., 2005). To improve the productivity of the rice wheat system, the wheat crop must be planted at the optimal time. Late planting not only reduces yield but also reduces the efficiency of the inputs applied to the wheat crop. The major cause of late wheat planting is the long turnaround time after the rice harvest. In order to overcome these problems many resource conservation technologies are practiced. These result in more efficient use of the natural resources used to produce a crop. Some of the major resource conservation technologies are:

Zero Tillage

Resource Conservation Technologies (RCTs) are co-evolving in participation with national and international scientists, farmers, private manufacturers and other stakeholders. Recent estimates suggest that these technologies now occupy around 2.0 a million hectares area under zero/reduced till. The ZT technology has several advantages over CT and some important ones includes saving of more than 90 % diesel, which comes to 61 litres/ha compared to conventional system. Thus, it reduces the cost of cultivation (Rs 3000/ha), saves forex, advances the time of wheat sowing (4-5 days), requires less water for the first irrigation and results in less infestation of Phalaris minor, which is a serious problem in northwest India. Besides this, it provides eco-friendly wheat cultivation by reducing 135 kg CO2/ha (assuming 2.6 kg CO2 production/ litre of diesel burnt), which is one of the major causes for global warming (Chauhan et al., 2001).

Surface Seeding

Surface seeding is the simples zero tillage system being followed which involves placement of wheat seed on to a saturated soil surface without any land preparation. This is a traditional farmer practice for wheat, legume and other crop establishment in eastern India and Bangladesh. Wheat seed is either broadcasted before the rice crop is harvested or after the harvest of the rice crop. Surface seeding of wheat on to unploughed, wet soil before or after rice harvest is working very well in heavy, poorly drained soils. This technique is particularly relevant to farmers with small land holding and little or no power sources (Hobbs et al., 2000). The key to success with this system is having the correct soil moisture at seeding. Once the roots germinate and extend in to the soil, the root can follow the saturation fringes as it drains down the soil profile. In China, farmers apply cut straw to mulch the soil, reduce evaporative losses of moisture and control the weeds (Yonglu et al., 2000; Gupta et al., 2000)

Reduced Tillage: A Better Option for RWCS

Reduced tillage is becoming popular among farmers around the globe. The practice is gaining popularity in rice-wheat cropping areas. It has been suggested that no till farming is more than just elimination of ploughing; it involves developing a complete package of agro-ecologically sound management practices to fit the overall schemes of farm systems trends of specific regions (Lal et al., 2004). The concept challenges the scientific basis of ploughing as an original universal method of soil preparation. From the plant breeding point of view, reduced tillage and its effects differ from those of conventional tillage in different ways (Joshi et al., 2007).

Ridge Tillage Systems

In bed planting, wheat or the other crops are planted on raised beds. This practice has increased dramatically in the last decade in the high yielding irrigated wheat areas of Mexico. The main reasons for the adopting of ridge

tillage systems in Mexico and elsewhere in world are as follows:

1. Management of irrigation water is improved

2. Bed planting facilitates irrigation before seeding and thus provides an opportunity for weed control before planting.

3. Plant stands are better

4. Weeds can be controlled mechanically, between the beds early in the crop cycle

5. Wheat seed rate is lower

6. Herbicide dependence is reduced and hand weeding and rouging are easier

7. Less lodging occurs

8. Beds provide better drainage and results in less water logging damage to wheat

Wheat Genotypic Requirement for the New RCTs

In areas where new resource conservation technologies are gaining popularity, farmers require cultivar adapted to the new practice (Joshi et al., 2004a, 2006). For surface seeding and reduced/zero tillage planting, the cultivar should posses faster root development to enable rapid establishment of the crop (Trethowan and Reynolds, 2005; Singh et al., 2007), thereby getting the seedling past an early and harsh environment and taking the best advantage of available soil moisture. Early studies failed to detect genotype x tillage practice interactions. The probable reasons for these conclusions may be of small number of genotypes tested and perhaps the fact that they were bred under conventional tillage (Trethowan and Reynolds, 2005). Recently significant genotype x tillage interactions was reported in tests involving diverse genotypes, requiring plant breeders involved in wheat improvement to tailor the genotype to different resource conservation technologies (Sharma et al., 1997; Sayre, 2002; Klein, 2003 and Singh et al., 2007). Watt et al. (2005) found that some of the varieties grew best in unploughed soil. They suggested that faster root growth, and vigorous genotypes may present opportunities for increased productivity under reduced tillage. The tillage x genotype interactions suggests that varietal development should be targeted to new RCT requirements (Joshi et al., 2007). Following this approach, wheat breeders of the CIMMYT have begun to select parental lines on the basis of performance under various tillage systems (Trethowan and Reynolds, 2005).

Tailoring Wheat Genotypes for Different Resource Conservation Technologies

Kronstad et al. (1978) suggested that to develop varieties of wheat adapted to different tillage options, some of the point of consideration are:

1. Growth factors influenced by tillage need to be identified

2. Genetic variability for growth factors affected by tillage must be large enough to provide sufficient selection scope

3. Selection criteria to identify superior lines in segregating populations must be established.

4. Progeny with improved characteristics for reduced tillage must possess all other desirable agronomic trait for an adapted and competitive cultivar.

Francis (1991) outlined the dimension of future cropping systems based on current trends and suggested that for a reduced tillage system having greater amounts of crop residue, possible plant breeding solution would be to incorporate increased seedling vigor, early stress tolerance (cold) and tolerance to eco-fallow/zero tillage practice. Another approach to breed crops for new RCTs would be to grow segregating populations from crosses involving parents that adapt well under such situations and incorporate useful traits like better emergence, profuse tillering and resistance to disease common under these situations (Joshi et al., 2007). However, for proper identification of segregating lines, these generations need to be grown under the targeted environment and practice.

Various plant breeding techniques have been advocated for improvement of crop plant with cropping system perspective. Singh and Huerta-Espino (2004) advocated a single backcross approach for effective shifting of a greater proportion of progenies in the segregating generations towards higher mean values thereby enhancing the chance of getting superior lines. Wang et al. (2003) showed that selected bulk approach gave slightly better genetic gain than other approaches. Showing segregating populations derived from selected bulks also appear attractive for wheat improvement for new RCTs. Several studies suggest new physiological tools can complement conventional breeding programmes (Fischer et al., 1998; Reynolds et al., 1998).

Input Use in Rice

Rice production consumes about 30% of all freshwater used worldwide. Flood-irrigated rice uses two to three times more water than other cereal crops such as wheat and maize. In Asia, flood-irrigated rice consumes more than 45 % of total freshwater used (Barker et al. 1999). The increasing water crisis threatens the sustainability of irrigated rice production (Gleick, 1993; Postel, 1997). By 2025, 15 out of 75 million hectare of Asia's flood-irrigated rice crop will experience water shortage (Tuong and Bouman 2003). Yet more rice needs to be produced with less and less water to feed the ever-growing population. Rice is an important target for water use reduction because of its relatively large water requirement compared to other crops (Wang et al, 2002; Tuoung and Bouman, 2003). Fortunately this aspect of rice cultivation is undergoing radical changes and technologies are being aggressively developed for more water productive cultivation practices. SRI, direct seeding under puddle soil, alternate wetting and drying, aerobic rice cultivation are some of these practices. Reducing crop duration without affecting productivity is another approach.

Cost of rice cultivation is mainly dependent on input costs and input use efficiency. At present the agronomic efficiency of input is about 25-30 % only. Per kg of nutrient applied 13.1 kg of rice is produce at present, which needs to be enhance to at least 18kg. Emphasis is needed on genetic enhancement to conserve natural resources and for higher input use efficiency of the genotypes. Variety Swarna was found to fairly well across locations both under N depriving and N abundant conditions. Similarly genotypes responsive to P, micronutrients, organic manure etc. needs to be developed or screened.

Aerobic Rice Cultivation

International Rice Research Institute (IRRI) developed the "aerobic rice technology" to address the water crisis problem in tropical agriculture. Because it is grown in soil with oxygen it is called "aerobic rice" as compared with anaerobic soil where oxygen is absent because of irrigation. In aerobic rice systems rice is grown like an upland crop with adequate inputs and supplementary irrigation when rainfall is insufficient (Bouman, 2001). The new concept of aerobic rice may be an alternate strategy, which combines the characteristics of both upland varieties with less water requirement and irrigated varieties with high response to inputs. The water use for aerobic rice production was 55-56 per cent lower than the flooded rice with 1.6-1.9 times higher water productivity and net returns to water use was two times higher. It indicates that aerobic rice may be viable option where the shortage of water does not allow the growing of lowland rice. Lafitte et al. 2002 reported that most lowland cultivars could survive in well-watered aerobic soils. Several technologies have been developed to reduce water loss and increase the water productivity of the rice crop. They are saturated soil culture (Borell et al. 1997), alternate wetting and drying (Li, 2001; Tabbal et al. 2002), ground cover systems (Lin et al. 2002) and system of rice intensification (Stoop et al. 2002). However, the fields are still kept flooded for some periods in most of these systems, so water losses remain high. Aerobic rice is high yielding rice grown under non-flooded conditions in non-puddled and unsaturated (aerobic) soil. It is responsive to high inputs, can be rainfed or irrigated, and tolerates (occasional) flooding (Bouman and Tuong 2001). There is need to address the physiological responses of rice to aerobic conditions and pay special attention to the yield components (Bouman et al. 2005). The suitable varieties for different agroecological situations should be screened or developed through breeding for aerobic rice cultivation. The available information indicated that where high yielding lowland rice varieties grown under aerobic soil conditions but with supplemental irrigation as a measure to save water have shown severe yield penalty (McCauley, 1990). Achieving high yields under irrigated but aerobic soil conditions require new varieties of aerobic rice that combine the drought resistant characteristics of upland varieties with high yielding characteristics of lowland varieties (Lafitte et al. 2002). The variety so developed should perform well both under aerobic condition as well as under normal irrigated condition, so that chance of getting a good harvest in a good rain fall year is not skipped.

System of Rice Intensification (SRI)

The SRI was developed in Madagascar by Fr. Henri de Lau Lanie in association with NGO- association Tefy Saina (ATS) and many small farmers in the 1980's is becoming popular in many countries including India. SRI is a system rather then a technology. It is based on the insight that rice has the potential to produce more tillers and grain than presently observed and that early transplanting along with optimal growth condition like wide spacing, optimum humidity, a vibrant healthy soil and aerobic soil conditions during vegetative growth can fulfill this potential (Uphoff, 2002). Water saving in SRI may be as high as 40 % compared to conventional practice. In a trial at DRR,

Hyderabad, SRI gave 16.6 % higher grain yield over normal transplanting. The varietal response to SRI and normal cultivation was wide. SRI method gave nearly 46 to 48 % higher yield in hybrids, 5.2 to 17 % in HYVs while negative results were observed incase of Pusa basmati due to its shy tillering habit under wider spacing. All the varieties are not promising for SRI cultivation method and response of cultivars to SRI varies as per their ability to exploit the natural resources. There is need to develop varieties that can give better response to SRI cultivation. A variety developed for SRI must have compact plant type, profuse tillering ability, better root system, bolder grains, low water requirement, responsive to organic inputs (use of inorganic inputs are 25 to 50% only) and resistance to pest and diseases. The significant aspect of the SRI cultivation is that the rice matures at about 10-15 days earlier compared to conventional practice and thereby vacate the land for timely sowing of succeeding wheat crop. Therefore, the genotypes used for SRI should be able to produce more with less duration.

Direct Seeded Rice

Direct dry seeding (DDS) in rice has advantage of faster and easier planting, reduced labour requirement and drudgery with earlier crop maturity by 7-10 days, better efficient water use and high tolerance of water deficit, less methane emission and higher income due to less cost of production (Balasubramanian and Hill, 2002). In both direct dry and wet seeded rice weed management is a major problem. Suitable genotypes needed to be developed for suitability under dry condition with better root system and competitiveness to weed. The genotypes with weed suppressing ability would a boon for the rice farmer's across the cultivation method and regions. Scientists are now able to identify some plant types that has the ability to compete successfully with weeds and give a good harvest even under no weeding condition. In North East variety Sahsarang 1 is said to have some abilities to compete with weeds. Development of such a genotypes would reduce the requirement for tillage, save labour and herbicide use and thereby conserving resource base in agriculture.

Organic Farming

For the attainment self sufficiency in the food grain production, we are in need of high yielding varieties in the place of local varieties. In the same, to produce organically we are in need of seed materials, which are very much responsive to organic and interact complementally with components of organic farming. About 65 per cent of our country's cropped area is not irrigated where the farming practices are still largely 'organic by default'. The use of chemical fertilizers is comparatively low in eastern and northeastern part of the country and yet there is sufficient food production. This defies the myth that the output would fall if the farmers go back to organic farming. It is high yielding varieties of seeds, which are important and not excessive chemical fertilizers and pesticides. However the organic farming in India is still in its infancy and due research efforts are required to support the various requirements of organic farming. Presently the varieties suited to conventional farming conditions are used in organic farming conditions also. The presence of conditions in organic farming that is different from conventional farming calls for developing varieties suitable for organic conditions. Efforts should be focused on use of organic in basmati rice where nitrogen requirement for the crop is less as compared to non basmati rice.

Conversion of Rice from C3 to C4 Crop

In C3 plants photorespiration reduces net carbon gain and productivity by as high as 40 %, as a result of this C3 plants are less competitive in certain environments. On the other hand C4 plants exhibit many desirable agronomic traits, high photosynthesis rate, faster growth and high water and input use efficiency. Therefore, efforts are on to convert rice to C4 crop for realizing higher photosynthesis rate and yield. Development of such a genotype would save a huge amount of water, which could be utilized for increasing irrigated area.

Biotechnological Interventions

Abiotic stresses adversely affect plant growth and development and are major constraints in enhancing plant productivity. Growing plants with enhanced tolerance to abiotic constraints will help in conserving agricultural resources. Among abiotic stresses drought, extreme temperatures, and saline soils are the most common stresses that plants encounter. Success in breeding for better adapted varieties to abiotic stresses depend upon the concerted efforts by various research domains including plant and cell physiology, molecular biology, genetics, and breeding. Recently large information has been generated on genetic systems related to plant adaptation under stress environments. The information can be used in molecular breeding and also the development of transgenics. Recently transgenics developed using genes conferring tolerance to osmotic stress such as DREB1, trehalose, LES proteins,

Mannitol etc have shown enhanced tolerance to drought. Genes related to signal transduction and membrane transport have used for developing salt and drought tolerance. Hence, genetic engineering for developing stress tolerant plants, based on the introgression of genes that are known to be involved in stress response and putative tolerance, might prove to be a faster track towards improving crop varieties. However, lot of work is to done to apply the transgene technology under field conditions. Once the technology is fully developed, it will save resources and enhance productivity of crop plants. Not only that, genetically engineered pants can be used in ameliorating soil conditions by absorbing toxic chemicals present in the soil. Therefore, biotechnology has great potential in conservation of agricultural resources.

Further increasing the yield potential of rice and wheat seems inevitable. This can be achieved by using hybrids, synthetics or improving the photosynthetic efficiency or crops. While traditional plant breeding has been effective improving the crop yields, biotechnology can make this more effective (Hobbs et al., 2000). Molecular tools derived with increasing knowledge about the molecular genomics bases of agronomic traits can be applied to develop improved cultivars that enable producers to increase the yields and quality.

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Session 1.7: Indigenous Knowledge and Practices

Blending Indigenous and Scientific Knowledge for Innovative CA Development using Participatory Action Research

H.J. Smith

ARC-Institute for Soil, Climate and Water, Private Bag X79, Pretoria, 0001, South Africa

(Email: hjsmith@arc.agric.za)

Sustainable agricultural systems which emphasize the use of practices such as Conservation Agriculture (CA), that integrate natural processes into food production and land rehabilitation, but simultaneously improve the livelihoods of farmers and contribute to the long-term sustainability of the resource base, hold the key to successful agricultural development. However, many of the processes that exist in sustainable agriculture systems, both biophysical and socio-economic, as well as their interactions, are complex and poorly understood and require an innovative approach of research and development. The ARC-ISCW has consequently adopted a systems approach that uses participatory action research (PAR)as a key methodology, which actively involves farmers in all stages of agricultural research and development. This approach aims to achieve the following two major outcomes: a) to integrate (blend) scientific and indigenous knowledge in CA design; and b) to improve the awareness and innovation capacity among various stakeholders, a critical ingredient for sustainable land management.

During the planning and design phase of a PAR project cycle, farmers and researchers have the opportunity to design interventions using their own experiences, blending indigenous and scientific knowledge and agreeing on the most appropriate systems to implement. A key PAR methodology in implementation is experimentation, especially on-farm, farmer-managed trials, with the following objectives: a) to improve experiential learning, b) to improve modification and dissemination of technologies to local farmers, c) to increase awareness among farming communities and d) to facilitate farmer-to-farmer extension and training.

Results show that the emphasis on improving the farmers' inherent capacity for experimentation is an important element in sustainable agricultural projects. Equiping farmers to select sustainable management options from a 'basket of CA principles and technologies' and developing capacity to experiment with and adapt these technologies, were found to be the key to the success of PAR projects. It was furthermore found that the intensive and prolonged interaction of farmers with project staff (especially researchers) was clearly important for blending indigenous and scientific knowledge and building experimentation skills.

PAR can have a major positive effect in developing local CA systems. By engaging farmers in a long enough period of experimentation, there is an emergence of innovation, self-learning and self organization, which are critical ingredients for adaptive management and sustainability. Furthermore, PAR links up (integrates) various system elements and stakeholders and thereby serves as a platform for social learning and local institution building. Finally, the principles and process of experiential and adult learning play a fundamental role in changing farmers' interest, paradigms and behaviour, which are key indicators of emerging sustainability.