0VERSITA
Biologia, Bratislava, 62/5: 542—546, 2007 Section Botany
DOI: 10.2478/s11756-007-0107-3
Assessing the microbiological, biochemical, soil-physical and hydrological effects of amelioration of degraded soils in semiarid Spain
Ma Teresa Hernandez Fernandez1, Jorge Mataix-Sülera2, Eubomír Lichner3, Vlasta Stekaürová3, Anton Zaujec4 & Carlos Garcia Izquierdo1
1 Centro de Edafología y Biologia Aplicada del Segura, Consejo Superior de Investigaciones Científicas (CEBAS CSIC), PO. Box 164, E-30100 Espinardo (Murcia), Spain; e-mails: mthernan@cebas.csic.es; cgarizq@cebas.csic.es 2GEA - Grupo de Edafología Ambiental, Universidad Miguel Hernandez, Avda del Ferrocarril s/n, E-03202 Elche (Alicante), Spain; e-mail: jorge.mataix@umh.es
3Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, SK-83102 Bratislava, Slovakia; e-mails: lichner@uh. savba. sk; stekauer@uh. savba. sk
4Department of Soil Science and Geology, Faculty of Agrobiology and Food Resources, Slovak Agricultural University, A. Hlinku 2, SK-94976 Nitra, Slovakia; e-mail: Anton.Zaujec@uniag.sk
Abstract: The way of improving degraded soils fertility and particularly of improving its microbial activity is to add "young" exogenous organic matter that contribute to provide labile organic matter to stimulate the life of the microorganisms existing in the soil. This organic matter will also improve both the retention and hydraulic characteristics of the degraded soils, all this contributing to soil restoration. In this study, the microbiological, biochemical, soil-physical and hydrological effects of the addition of a municipal solid waste compost to a degraded soil in El Campello, SE Spain were evaluated in a field experiment. Soil samples from experimental plots were analyzed 6 and 18 months after soil amendment. In both sampling time treated plots showed significantly higher microbial biomass carbon and dehydrogenase activity values than control, indicating that soil microbial population's development and activity were stimulated by compost addition, this effect being not ephemeral but lasting in the time. Soil urease activity was not affected by compost addition while protease hydrolysing N-a-benzoil-L-argininamide (BAA) activity was strongly stimulated by the incorporation of compost into the soils. Phosphatase and ,3-glucosidase activities were also stimulated by the organic amendment, this stimulation being particularly noticeable 18 months after the compost addition. Nevertheless, this increase in soil microbial populations and activity did not result in an increase in soil aggregation and hydrological parameters. This can be due to the high content of carbonates and Ca2+ ions in these calcareous soils, that lead to an initially high content of water-stable macroaggregates.
Key words: amelioration; degraded soil; sewage sludge compost
Introduction
In the Mediterranean region of SE Spain both intensive agricultural practices and the agricultural use of marginal lands, which are very susceptible to environmental degradation and unsuitable for crop production, have led to a loss of soil quality and fertility and the subsequent land abandonment and soil degradation. The Mediterranean region contains, therefore, large areas of low quality soils with little plant cover, which only adds to their degree of degradation. One of the key factors is, indeed, the low organic matter content of the soils in the region, and there is no need to reiterate the close relationship that exists between this parameter and soil fertility.
In this Mediterranean region soil degradation is aggravated by the adverse environmental factors existing in the area such as climate, relief, lithological substrate and low plant cover (the extent of soil degradation is an accurate reflection of the state of its plant cover). So, in SE Spain climate is characterized by long periods of drought interrupted by heavy, occasionally torrential, rainfall, which can be the cause of severe erosion. The sloping landscape also favours erosion, the degree of which will depend on rainfall intensity, plant cover, and the use to which it is put. As regards lithologi-cal substrate, the most widely represented in SE Spain are carbonated rocks, quaternary sediments and loams, which give rise to soils prone to erosion and to others negative processes, and low plant cover density.
* Presented at the International Conference on Bioclimatology and Natural Hazards, Pol'ana nad Detvou, Slovakia, 17-20 September 2007.
©2007 Institute of Botany, Slovak Academy of Sciences
Springer
Table 1. Characteristics of the studied (non-amended) soil (dry weight).
Soil parameter Value
Sand (%) 26.7
Silt (%) 42.0
Clay (%) 31.3
CO3~ equivalent (%) 48.8
pH(H2O) (1:2.5 w/v) 8.14
Electrical conductivity (^S cm-1) 300
Total organic carbon (%) 1.38
Available P (g kg-1) 0.008
Available Na (g kg-1) 1.4
Available K (g kg-1) 2.6
Available Ca (g kg-1) 34.9
Available Mg (g kg-1) 1.6
Table 2. Characteristics of the sewage sludge compost used (dry weight).
Parameter Value
Organic matter (%) 44.9
pH 1 6.9
Electrical conductivity (^S cm 1) 4250
N-Kjeldahl (g kg-1) 24.9
Total Phosphorus (g kg-1) 17.3
Total Na (g kg-1) 14.5
Total K (g kg-1) 22.0
Total Ca (g kg-1) 289
Total Mg (g kg-1) 57
Total Fe (mg kg-1) 7388
Total Mn (mg kg-1) 303
Total Cu (mg kg-1) 137
Total Zn (mg kg-1) 435
The way of improving the fertility of these degraded soils and particularly of improving its microbial activity, is to add exogenous organic matter that contributes to provide labile organic matter in sufficient amount to stimulate the life of microorganisms existing in the soil (Ros et al. 2001, 2003). As increased total organic carbon content is, with a few exceptions, positively correlated with increased aggregate stability (Tisdall & Oades 1982), the addition of municipal solid waste compost should improve both the retention and hydraulic characteristics of the studied soil.
The aim of this study was to assess the microbiological, biochemical, soil-physical and hydrological effects of addition of municipal solid waste compost to a degraded soil in El Campello (SE Spain).
Material and methods
Six 2 x 2 m plots were set out in a degraded area situated in El Campello (Alicante), SE Spain. The degradation of this soil is due to previous land uses such as agricultural and latter abandonment. The recovery of natural vegetation is slow, mainly due to the semiarid conditions (the annual rainfall lower than 300 mm, irregularly distributed as torrential rainfall events), and soil is far from climax conditions. Three of these plots, randomly distributed, were amended with 60 t/ha (wet weight) of sewage sludge compost in March 2004, and the other three remained unamended. The soil was a clay loam textured Ari-Anthropic Regosols (WRB 1994). Soil and composts characteristics are shown in Tables 1 and 2, respectively.
Plots were sampled 6 and 18 months after soil amendment in order to assess the effect of compost addition on soil microbiological, biochemical, soil-physical and hydrological properties. Soil samples were collected from the top layer (0-15 cm), each sample being the mixture of 8 soil subsam-ples. Due to the extreme scarcity of rainfall, all plots were irrigated every 10th days using 4 litres m-2 (4 mm) in June, July and August 2005. This irrigation was carried out in order to simulate a year with a more normal quantity of rain, since this year was extremely dry.
The dilution technique (Kopcanova et al. 1990) in the 1:10000 (KTJ) ratio in three repetitions was used to determine the species diversity of the soil microscopic fungi.
The microscopic fungi were cultivated in the Czapek-Dox agar, Sabourad agar, and Jensen agar, and their genera and species were determined according to macro- and micromor-phological structures (Domsch et al. 1980).
Total organic carbon (TOC) was determined by the Yeomans & Bremner (1989) method, and microbial biomass C (MBC) by the fumigation-extraction method (Vance et al. 1987). Dehydrogenase activity was estimated by a modification of the method reported by Von Mersi & Schinner (1991), (Garcia et al. 1997). Urease activity was estimated by the buffered method described by Kandeler & Gerber (1988), the activity of the protease hydrolysing N-a-benzoil-L-argininamide (protease-BAA) following the Nannipieri et al. (1980) method, phosphatase activity by the Tabatabai & Bremner (1969) method, and ,3-glucosidase activity by the method of Eivazi & Tabatabai (1987).
Soil pH and electrical conductivity were measured by standard electrode methods. Bulk density was determined on 100 cm3 soil samples after drying to constant weight at 105 °C. Soil aggregate stability was determined by the rainfall simulator method used by Roldan et al. (1994). Dry aggregation is an important phase of structure genesis in arid and semiarid soils, as it determines the resistance of soil to wind erosion. Dry stability measures the strength of aggregates subjected to fracture and abrasion. The measurements of stability to water are generally used to estimate structural changes due to cultivation, because water is the main agent of aggregate breakdown in agricultural soils. Mean weight diameter (MWD) of stable macroaggre-gates was determined from content of their fractions after dry sieving and MWD of water-stable aggregates wet sieving by the Bakshajev method (Hrasko et al. 1962). The sieve meshes were 3.0, 1.0, 0.5, and 0.25 mm, and calculation was based on a summation of the weight of different aggregate-size fractions compared with the total soil weight used. Water retention capacity of the studied clay loam soil was calculated from the retention curve as the soil water content at soil moisture potential hw = —400 cm (Kutilek & Nielsen 1994). Saturated hydraulic conductivity Ks was estimated in field conditions using a standard double ring ponded (pressure head ho = +2 cm) infiltration experiment. The double-ring infiltrometer had the inner-ring diameter of 10 cm, the buffer ring diameter of 20 cm, and the length of 20 cm. Saturated hydraulic conductivity Ks was also estimated in the laboratory on 100 cm3 samples by the falling head method (Kutilek & Nielsen 1994).
Table 3. Differences in microbiological, biochemical, soil-physical and hydrological parameters between treated and control plots in El Campello.
September 2004
September 2005
Soil characteristics
Control plots
Treated plots
Control plots
Treated plots
Total organic carbon content (%) 1.38 ± 0.09* 1.87 ± 0.15* 1.43 ± 0.11* 2.65 ± 0.03*
Microbial biomass carbon content 256.56 ± 25.97* 327 ± 11.93* 130.64 ± 28.99* 269.78 ± 27.9*
(mg kg-1 soil)
Dehydrogenase activity (ug INTF 2.84 ± 0.38* 4.52 ± 0.50* 3.18 ± 0.55* 5.28 ± 0.39*
g soil-1 h-1)
Urease activity (umol N-NH+ g 1.32 ± 0.10 1.05 ± 0.16 2.67 ± 0.32 2.83 ± 0.08
soil-1 h-1)
Protease activity (umol N-NH+ g 1.10 ± 0.05* 1.86 ± 0.31* 2.21 ± 0.10* 3.96 ± 0.21*
soil-1 h-1)
Phosphatase activity (umol PNP 2.06 ± 0.12* 2.34 ± 0.22* 3.71 ± 0.72* 4.44 ± 0.84*
g soil-1 h—1)
3—Glucosidase activity activity 1.62 ± 0.18 1.61 ± 0.29 2.20 ± 0.43* 2.84 ± 0.22*
(umol PNP g soil-1 h-1)
pH 1 8.35 ± 0.02* 8.16 ± 0.10* 8.11 ± 0.04 7.97 ± 0.13
Electrical conductivity (uS cm 1) 232 ± 12 271 ± 27 453 ± 82 518 ± 161
Bulk density (g cm-3) 0.96 ± 0.01* 0.92 ± 0.02* 0.95 ± 0.01* 0.91 ± 0.01*
Aggregate stability (%) 48 ± 2 49 ± 3 42 ± 7 43 ± 6
Water-stable macroaggregates (%) 82.8 ± 5.0 72.1 ± 4.6 84.1 ± 2.2 78.6 ± 2.7
Mean weight diameter (mm) of 1.061 ± 0.116 1.049 ± 0.057 1.609 ± 0.084 1.529 ± 0.214
macroaggregates after dry sieving
Mean weight diameter (mm) of 1.243 ± 0.172 0.990 ± 0.057 1.323 ± 0.174 1.260 ± 0.201
macroaggregates after wet sieving
Retention capacity of soil 0.2384 ± 0.0332 0.2484 ± 0.0141 0.2796 ± 0.0091 0.2639 ± 0.0159
(cm3 cm-3)
Saturated hydraulic conductivity (2.77 ± 0.99) X 10-5 (1.05 ± 1.09) X 10-5 (1.11 ± 1.22) X 10-5 (1.25 ± 0.70) X 10-5
(laboratory) (m s-1 )
Saturated hydraulic conductivity (6.93 ± 2.09) X 10-5 (6.26 ± 1.94) X 10-5 (9.26 ± 1.99) X 10-5 (8.64 ± 2.37) X 10-5
(field) (m s-1)
*: significant differences (P < 0.05) between amended and unamended soil at a given sampling time.
Results and discussion
Microbiological and biochemical measurements Few months after soil amendment spontaneous vegetation appeared in the amended soil, which was denser the second year of the experiment. Vegetation developed in the unamended soils was much scarcer than that of amended soils, particularly at the second year.
In spite of the fact that part of the organic matter added to the soil with the organic amendment must have been mineralised during the time elapsed from compost addition to the plot sampling, amended plots showed higher values of TOC than unamended plots at the two sampling times (Table 3). This fact can be due to both the non decomposable fraction of the organic matter added with the compost, and the contribution of root exudates and plant debris from the more dense vegetal cover developed in the amended plots.
MBC can be used more effectively than TOC content as an indicator of soil quality changes since it responds more rapidly and with a higher degree of sensitivity to any soil disturbance (Garcia et al. 2000). Six months after compost addition, treated plots showed significantly higher MBC values than control ones (Table 3), suggesting that, even under the adverse climatic conditions following the soil amendment (very dry conditions), compost addition had stimulated the
development of soil microbial populations, which is of paramount importance for ecosystem functioning. Compost addition also contributes to soil MBC with the microbial populations it contains.
Eighteen months after the organic amendment, MBC content in the treated soils remained higher than in the control soil, indicating that the stimulating effect of the organic amendment on the microbial population development is durable. Differences in genera and species of soil microscopic fungi were also observed between amended and unamended soils six months after soil amendment (Table 4).
The overall metabolic microbial activity was evaluated by measuring dehydrogenase activity (Garcia et al. 1997). Dehydrogenase activity was significantly higher in treated than in control soils, suggesting that the organic amendment increased soil microbial activity (Table 3). This effect was maintained 18 months after compost addition, indicating that the microbial soil quality improvement obtained was not ephemeral but lasting in the time.
The degradation of the organic matter is largely due to hydrolytic processes. For this reason, it seemed interesting to determine some hydrolases, which, despite being specific enzymes (Nannipieri et al. 1990), may help to explain the cycle of such important elements as N (ureases and proteases), P (phosphatases)
Table 4. Soil microscopic fungi species detected in treated and control plots six months after soil amendment (September 2004).
Microfungi species Control plots Treated plots
Actinomucor elegans + +
Alternaría sp. +
Alternaria alternata +
Alternaria tenuissima +
Aspergillus sp + +
Aspergillus flavus + +
Aspergillus fumigatus + +
Aspergillus terreus +
Aureobasidium pullulans +
Chaetomium sp. + +
Eurotium herbariorum +
Fusarium graminearum +
Fusarium culmorum +
Fusarium sporotrichioides +
Humicola sp. +
Humicola fuscoatra +
Humicola grisea +
Mortierella sp. + +
Penicillium sp. + +
Penicillium expansum + +
Penicillium frequentans + +
Rhizous arrhizus + +
Scopulariopsis brevicaulis + +
Scopulariopsis fusca +
Stachybotrys elegans + +
Stachybotrys charatarum +
Mycelia sterilia + +
and C (,3-glucosidases).
Urease hydrolyses urea-type substrates to CO2 and ammonium, and protease BAA acts in the hydrolysis of proteins to NH+ using simple peptides as substrates. Soil urease activity was not affected by compost addition (Table 3). This suggests that the added compost was poor in substrates type urea and that the formation of this substrate with time is not stimulated by compost addition. Conversely, protease BAA activity was strongly stimulated by the incorporation of compost. Differences in protease activity between the treated and control soils were significantly greater 18 months after the organic amendment, which matches with the increase in microbial activity observed in these samples, as measured by dehydrogenase activity, and can be explained by the higher amount of carbon sources entering in the system through plant remains and root exudates in the treated plots with respect to the control plots. Data from urease and protease BBA activity show that the functioning of the N cycle has been modified by the addition of the organic amendment (Nannipieri et al. 1990). Phosphatase catalyses the hydrolysis of P organic compounds to inorganic P forms available to plants. The activity of this enzyme was stimulated by the organic amendment. This stimulation was particularly noticeable 18 months after the compost addition (Table 3). ,3-glucosidase catalyses the hydrolysis of carbohydrate ,3-glucoside bonds contributing to the release of energy for soil microbial activity (Eivazi & Zakaria 1993). Six months after soil amendment, the treated and control soils showed similar values of ,3-glucosidase
activity. However, 18 months after the amendment the synthesis of this enzyme was stimulated in the amended plots (Table 3). The addition of compost favoured the apparition of a denser vegetal cover, but due probably to the adverse climatic conditions existing during the first six months of the experiment, differences in plant cover density were not great enough to establish differences in ,3-glucosidase activity stimulation. After 18 months differences in plant cover were greater and the higher amount of root exudates and plant debris existing in the treated plots contributed to stimulate the synthesis of this enzyme.
Physical, chemical and hydrological parameters Slight differences in soil pH were found at the first sampling, with lower values in treated plots (Table 3). However, no significant differences in EC were observed between amended and unamended soils, suggesting that the first spring rainfall events lixiviated the soluble salts incorporated with the compost. EC values were higher at the second than at the first sampling, probably due to salt solubilisation by the irrigation treatments applied during summer.
Bulk density decreased slightly with compost addition, which is in agreement with previous findings (Garcia-Orenes et al. 2005), indicating a slight improvement of soil structure, which can be a kind of dilution effect due to addition of OM to mineral soil. However, no statistical differences in aggregate stability were found between amended and unamended soils (Table 3). Similar results were obtained by Zaujec & Simansky (2006).
It is well-known that organic matter enhances soil microbial activity that transforms the newly added organic matter into polysaccharides and long chain aliphatic compounds capable of binding and stabilizing aggregates (Graber et al. 2006). But in the case of the studied calcareous soil with high content of soil inorganic carbon and Ca2+ cations, which play dominant role in aggregation processes, the addition of organic matter had less effect on aggregation processes due to the initial high content of water-stable macroag-gregates (Dimoyiannis et al. 1998; Boix-Fayos et al. 2001).
Saturated hydraulic conductivity and retention capacity of the studied soil were not affected by compost addition (Table 3). This could result from the small effect of compost addition on aggregation processes in this particular soil, due to its high initial content of water-stable macroaggregates. An increase in saturated hydraulic conductivity could be expected after formation of the surface-vented macropores by vegetation and soil animals (Kodesova et al. 2006).
We can conclude that application of the sewage sludge compost to a degraded soil resulted in an increase in total organic carbon, microbial biomass carbon and microbial activity, but it did not bring an expected increase in the water-stable macroaggregates due to an initially high content of water-stable macroag-gregates.
Acknowledgements
The authors thank Dr. Pavel Dlapa (Department of Soil Science, Faculty of Natural Science, Comenius University, Bratislava, Slovakia) for his assistance in field measurements, and Dr. Olivia Dugova (Institute of Landscape Ecology SAS, Bratislava) for microfungi determination. The financial support from Slovak Scientific Grant Agency Projects Nos 2/6003/26 and 2/5018/25, and the Spanish-Slovak Project No. 2004SK0003 (Spanish Council of Scientific Research, CSIC - Slovak Academy of Sciences) is gratefully acknowledged.
References
Boix-Fayos C., Calvo-Cases A. & Imeson A.C. 2001. Influence of soil properties on the aggregation of some Mediterranean soils and use of aggregate size and stability as land degradation indicators. Catena 44: 47—67. Dimoyiannis D.G., Tsadilas C.D. & Valmis S. 1998. Factors affecting aggregate instability of Greek agricultural soils. Agrochimica 41: 97-108. Domsch K.H., Gams W. & Anderson T.H. 1980. Compendium of
soil fungi. Academic Press, London, 859 pp. Eivazi F. & Tabatabai M.A. 1987. Glucosidases and galactosi-
dases in soils. Soil Biol. Biochem. 20: 601-606. Eivazi F. & Zakaria A. 1993. Beta-glucosidase activity in soils amended with sewage-sludge. Agric. Ecosyst. Environ. 43: 155-161.
Garcia C., Hernandez T. & Costa F. 1997. Potential use of de-hydrogenase activity as an index of microbial activity in degraded soils. Comm. Soil Sci. & Plant Anal. 28: 123-135. Garcia C., Hernandez T., Pascual J.A., Moreno J.L. & Ros M. 2000. Microbial activity in soils of SE Spain exposed to degradation and desertification processes. Strategies for their rehabilitation, pp. 93-143. In: Garcia-Izquierdo C. & Hernandez M.T. (eds), Research and Perspectives of Soil Enzymology in Spain. CEBAS CSIC, Espinardo. Garcia-Orenes F., Guerrero C., Mataix-Solera J., Navarro-Pedreno J., Gomez I. & Mataix-Beneyto J. 2005. Factors controlling the aggregate stability and bulk density in two different degraded soils amended with biosolids. Soil & Tillage Research 82: 65-76. Graber E.R., Fine P. & Levy G.J. 2006. Soil stabilization in semiarid and arid land agriculture. J. Materials in Civil Engineer. 18: 190-205.
Hrasko J., Cervenka L., Facek Z., Komar J., Nemecek J., Posplsil F. & Sirovy V. 1962. Methods of soil analysis. SVPL, Bratislava, 335 pp. (in Slovak)
Kandeler E. & Gerber H. 1988. Short-term assay of soil urease activity using colorimetric determination of ammonium. Biol. Fertil. Soils 6: 68-72
Kodesová R., Kodes V., Zigová A. & Simunek J. 2006. Impact of plant roots and soil organisms on soil micromorphology and hydraulic properties. Biologia 61(Suppl. 19): S339-S343.
Kopcanová E., Rehorková V. & Bumbala E. 1990. Guide of microbiology for phytotechnicians. Príroda, Bratislava, 128 pp. (in Slovak)
Kutilek M. & Nielsen D.R. 1994. Soil hydrology. Catena Verlag, Cremlingen-Destedt, 370 pp.
Nannipieri P., Ceccanti B., Cervelli S. & Matarese E. 1980. Extraction of phosphatase, urease, protease, organic carbon and nitrogen from soil. Soil Sci. Soc. Amer. J. 44: 1011-1016.
Nannipieri P., Grego S. & Ceccanti B. 1990. Ecological significance of biological activity in soil. In: Bollag J.M. & Stotzky G. (eds), Soil Biochem. 6: 293-355.
Roldan A., Garcia-Orenes F. & Lax A. 1994. An incubation experiment to determinate factors involving aggregation changes in an arid soil receiving urban refuse. Soil Biol. Biochem. 26: 1699-1707.
Ros M., Hernández T. & Garcia C. 2001. The use of urban organic wastes in the control of erosion in a semi-arid mediterranean soil. Soil Use & Managem. 17: 292-293.
Ros M., Hernández T. & Garcia C. 2003. Soil microbial activity after restoration of a semi-arid soil by organic amendments. Soil Biol. Biochem. 35: 463-469.
Tabatabai M.A. & Bremner J.M. 1969. Use of p-nitrophenol phosphate in assay of soil phosphatase activity. Soil Biol. Biochem. 1: 301-307.
Tisdall J.M. & Oades J.M. 1982. Organic matter and water-stable aggregates in soils. J. Soil Sci. 33: 141-163.
Vance E.D., Brookes P.C. & Jenkinson D.S. 1987. An extraction method for measuring soil microbial biomass C. Soil Biol. Biochem. 19: 703-707.
Von Mersi W. & Schinner F. 1991. An improved and accurate method for determining the dehydrogenase activity of soils with iodonitrotetrazolium chloride. Biol. Fertil. Soils 11: 216220.
WRB 1994. World Reference Base for Soil Resources. Wagenin-gen/Rome, 161 pp.
Yeomans J. & Bremner J.M. 1989. A rapid and precise method for routine determination of organic carbon in soil. Commun. Soil Sci. Plant Anal. 19: 1467-1476.
Zaujec A. & Simansky V. 2006. The influence of bio-agents on decay of plant residues, soil structure and soil organic matter. Slovak Agricultural University Nitra, 111 pp. (in Slovak)
Received April 16, 2007 Accepted June 27, 2007
