Soil amendments with organic wastes reduce the toxicity of nickel to soil enzyme activities

The effects of adding a crushed cotton gin compost (CCGC) and poultry manure (PM) on the biological properties of a Typic Xerofluvent soil contaminated with Ni were studied in the laboratory. Urease, BBA-protease, alkaline phosphatase, β-glucosidase and arylsulfatase activities were measured in soils containing seven concentrations (100, 250, 500, 1000, 2500, 5000 and 8000 mg kg⁻¹ soil) of Ni after four incubation times (1 day, 7 days, 15 days and 45 days). The resulting inhibition was compared with that of the enzymatic activities in the same soil containing similar concentrations of the Ni but amended with crushed cotton gin compost and poultry manure. The 50% ecological dose (ED₅₀) values were calculated by the two kinetic models used by Speir et al. [T.W. Speir, H.A. Kettles, A. Parshotam, P.L. Searle, L.N.C. Vlaar, A simple kinetic approach to derive the ecological dose value, ED50, for the assessment of Cr(VI) toxicity to soil biological properties, Soil Biol. Biochem. 27 (1995) 801–810] and by the sigmoidal dose–response model used by Haanstra et al. [L. Haanstra, P. Doelman, J.H. Oude Voshaar, The use of sigmoidal dose response curves in soil ecotoxicological research, Plant Soil 84 (1985) 293–297]. The urease, BBA-protease, β-glucosidase, alkaline phosphatase and arylsulfatase activities were higher in the organic amended soils (76%, >99.7%, >95.7%, >27.6% and >87.2%, respectively) than in the control soil. Also, the enzymatic activities were higher in CCGC-amended soils than in the PM-amended soils (51%, 20%, 11.2%, and 11.3% increase for urease, BBA-protease, β-glucosidase and alkaline phosphatase, respectively). For all soil enzymatic activities and at the end of the period of incubation, the ED₅₀ values were lowest in control soil, followed by PM and CGCC-amended soils. This may have been due to the adsorption capacity of Ni being higher in the humic acid (CGCC) than in the fulvic acid-amended soil (PM).     

Assessing air-drying and rewetting pre-treatment effect on some soil enzyme activities under Mediterranean conditions

Soil enzyme activities are useful indicators of soil quality as they are very sensitive to disturbance. Sample storage or pre-treatments could affect the results in these assays, which are normally determined in fresh samples, kept cold or frozen. The objectives of this study were to (i) evaluate the effect of air-drying or air-drying and rewetting on β-glucosidase, acid phosphatase and urease activities in soils from different locations, degradation status and sampling seasons, and (ii) assess if air-drying or air-drying and rewetting is an accurate sample storage and pre-treatment procedure for enzyme activities in soil quality evaluations under semiarid Mediterranean conditions. Our results showed that urease, phosphatase and β-glucosidase activities were hardly affected by air-drying of degraded and non-degraded soils from the two locations studied in all seasons. Short incubations (4, 8 and 12 d at 23 °C) of rewetted air-dried soil at 55% of water-holding capacity showed different patterns depending on the enzyme studied. Urease and β-glucosidase activities were relatively stable during incubation, with several significant (P<0.05) shifts up and down in some soils and samplings. However, acid phosphatase showed an increase in activity with incubation, of between 5% and 50% relative to air-dried samples. These increases followed no pattern and were unrelated to soil characteristics or sampling date. Hence, urease, phosphatase and β-glucosidase activities determined in air-dried soil samples seem to be representative of those obtained under field-moist conditions. In contrast, short incubations of rewetted soil samples can produce fluctuations in these enzyme activities, mainly of acid phosphatase, and estimations in these conditions are not so representative of field-moist soil values.     

Microbial activity and hydrolase synthesis in long-term Cd-contaminated soils

Alkaline and acid phosphomonoesterase, β-glucosidase, arylsulfatase, protease and urease activities, CO₂-C evolution and ATP content were monitored in long-term Cd-contaminated (0-40 mg Cd kg⁻¹ dry weight soil) sandy soils, kept under maize or ‘set aside’ regimes, amended with plant residues. The organic matter input increased soil respiration, ATP contents and hydrolase activities in all soils. However, the Cd-contaminated soils had significantly higher metabolic quotients (qCO₂), as calculated by the CO₂-to-ATP ratio, and significantly lower hydrolase activities and hydrolase activity-to-ATP ratios for alkaline phosphomonoesterase, arylsulfatase and protease activities, compared with the respective uncontaminated soils. The ratios between acid phosphomonoesterase, β-glucosidase and urease activities and ATP were unaffected. A significantly higher qCO₂/μ ratio, an expression of maintenance energy, was observed in most of the contaminated soils, indicating that more energy was required for microbial synthesis in the presence of high Cd concentrations. It was concluded that exposure to high Cd concentrations led to a less efficient metabolism, which was responsible for lower enzyme activity and synthesis and lower hydrolase activity-to-ATP ratios observed in these Cd-contaminated soils.     

Microbiological rates and enzyme activities as indicators of functionality in soils affected by the Aznalcóllar toxic spill

This study focused on the potential of using soil enzyme activities and general microbiological rates (respiration, N-mineralisation, nitrification) to evaluate the quality of soils affected by a pyrite mud spill which contained high concentrations of heavy metals. The quality of soils after restoration was estimated by comparing enzyme activities and general microbiological rates in three different types of experimental field plots: (i) non-polluted, (ii) polluted but restored, and (iii) polluted but un-restored soils. Non-polluted soils showed the highest levels of enzyme activity. Significant differences were detected for acid phosphatase, β-glucosidase and urease activities between all types of plots. However, arylsulfatase and alkaline phosphatase activities showed no significant differences between the restored plots and polluted but un-restored plots. Geometric mean statistics were used as an index of soil quality in terms of overall: (i) bioavailable heavy metal concentrations, (ii) assayed enzyme activities, and (iii) general microbiological rates, in order to compare plots differing in the degree of pyritic mud pollution. The results indicate that it is important to consider these three criteria in to estimate the soil quality of heavy-metal contaminated soils. Typically, enzyme activities were negatively correlated with bioavailable Cd, Cu and Zn concentrations, but positively with soil pH values. In contrast, pH values were negatively correlated with bioavailable concentrations of Cd, Cu and Zn. It is unclear if the generalised lower enzyme activities found in restored soils, compared to non-polluted soils, is promoted by pH or bioavailable heavy metals concentrations, or a combination of both.     

Phyllostachys edulis (moso bamboo) rhizosphere increasing soil microbial activity rather than biomass

Purpose

Rhizosphere and fertilization might affect soil microbial activities, biomass, and community. This study aimed to evaluate the impacts of Phyllostachys edulis (moso bamboo) rhizospheres on soil nutrient contents and microbial properties in a moso bamboo forest with different fertilizer applications and to link soil microbial activities with abiotic and biotic factors.

Materials and methods

The experiment included three treatments: (1) application of 45% slag fertilizer (45%-SF); (2) application of special compound fertilizer for bamboos (SCF); and (3) the control without any fertilizer application (CK). Simultaneously, bulk soils and 0.5, 2.5, 4.5, and 6.5-year-old (y) bamboo rhizosphere soils were selected. Soil nutrient contents were analyzed. Microbial activities were evaluated based on the activities of soil enzymes including β-glucosidase, urease, protease, phosphatase, and catalase. The total microbial biomass and community were assessed with the phospholipid fatty acids (PLFAs) method.

Results and discussion

In the CK and SCF treatments, organic matter contents of rhizosphere soils were significantly higher than those of bulk soils. Soil β-glucosidase, urease, protease, phosphatase, and catalase activities in rhizosphere soils were higher than those of bulk soils, with the sole exception of β-glucosidase of 0.5 y rhizosphere soil in the 45%-SF treatment. Compared with the CK treatment, fertilizer applications tended to increase soil total PLFAs contents and changed soil microbial community. Moso bamboo rhizospheres did not significantly increase the total microbial biomass. In the SCF treatment, the Shannon index of bulk soil was significantly lower than those of rhizosphere soils.

Conclusions

Our results suggested that both rhizospheres and fertilizer applications could change the soil microbial community structures and that moso bamboo rhizosphere could increase microbial activity rather than biomass in the forest soils with different fertilizer applications.

     

A soil quality index based on the equilibrium between soil organic matter and biochemical properties of undisturbed coniferous forest soils of the Pacific Northwest

Recent studies have suggested that the organic matter contents of undisturbed soils (under natural vegetation) are in equilibrium with biological and biochemical properties. Accordingly, we hypothesised that such equilibria should be disrupted when soils are subjected to disturbance or stress, and that measurement of this disruption can be expressed mathematically and used as a soil quality index. In this study, we evaluated these hypotheses in soils from the H.J. Andrews Experimental Forest in Oregon. Both O and A horizons were sampled from nine sites in Spring 2005 and Fall 2006. Soil samples were analyzed for enzyme activities (phosphatase, β-glucosidase, laccase, N-acetyl-glucosaminidase, protease and urease), and other biological and chemical properties including N-mineralization, respiration, microbial biomass C (MBC), soil organic carbon (SOC) and total nitrogen content. In addition, soil samples from one old-growth site were manipulated in the laboratory to either simulate chemical stresses (Cu addition or pH alteration) or physical disturbances (wet-dry or freeze-thaw cycles). The results showed variation in biological and biochemical soil properties that were closely correlated with SOC. Multiple regression analysis of SOC levels against all soil properties showed that a model containing only MBC and phosphatase activity could account for 97% of the SOC variation among the sites. The model fit was independent of spatial and temporal variations because covariates such as site, stand age, sampling date, and soil horizon were found to be not statistically significant. Although the application of stress/disturbance treatments inconsistently affected most of the individual biochemical properties, in contrast, the ratio of soil C predicted by the model (C_p), and soil C measured (C_m) was consistently reduced in soils submitted to at least one level of stress and disturbance treatments. In addition, C_p/C_m was more affected in soils submitted to wet-dry cycles and Cu contamination than to freeze-thaw cycles or shifts in soil pH. Our results confirm previous evidence of a biochemical balance in high quality undisturbed soils, and that this balance is disrupted when the soil is submitted to disturbances or placed under stress conditions. The C_p/C_m ratio provides a simple reference value against which the degrading effects of pollutants or management practices on soil quality can be assessed.     

Influence of long-term residue management on soil enzyme activities in relation to soil chemical properties of a wheat-fallow system

Summary Soil enzyme activities (acid and alkaline phosphatase, arylsulfatase, -glucosidase, urease and amidase) were determined (0- to 20-cm depth) after 55 years of crop-residue and N-fertilization treatment in a winter wheat (Triticum aestivum L.)-fallow system on semiarid soils of the Pacific Northwest. All residues were incorporated and the treatments were: straw (N₀), straw with fall burn (N₀FB), straw with spring burn (N₀SB), straw plus 45 kg N ha^–1 (N₄₅), straw plus 90 kg N ha^–1 (N₉₀), straw burned in spring plus 45 kg N ha^–1 (N₄₅SB), straw burned in spring plus 90 kg N ha^–1 (N₉₀SB), straw plus 2.24 T ha^–1 pea-vine residue and straw plus 22.4 T ha^–1 of straw-manure. Enzyme activities were significantly (P<0.001) affected by residue management. The highest activities were observed in the manure treated soil, ranging from 36% (acid phosphatase) to 190% increase in activity over the control (N₀). The lowest activities occurred in the N₀FB (acid phosphatase, arylsulfatase and -glucosidase) and N₉₀ treated soils (alkaline phosphatase, amidase and urease). Straw-burning had a significant effect only on acid phosphatase activity, which decreased in spring burn treated soil when inorganic N was applied. Urease and amidase activity decreased with long-term addition of inorganic N whereas the pea vine and the manure additions increased urease and amidase activity. There was a highly significant effect from the residue treatments on soil pH. Arylsulfatase, urease, amidase and alkaline phosphatase activities were positively correlated and acid phosphatase activity was negatively correlated with soil pH. Enzyme activities were strongly correlated with soil organic C and total N content. Except for acid phosphatase, there was no significant relationship between enzyme activity and grain yield.Journal Paper No. 8072 of the Agricultural Experimental Station, Oregon State University, Corvallis, OR 97331, USA     

半干旱退化土壤中施入城市垃圾的长期效应研究

The addition of municipal solid wastes (MSW) is considered as a possible strategy for soil rehabilitation in southeast Spain. The objective of this study was to evaluate the long-term (17 years) effect of five doses of MSW addition on the microbiological, biochemical, and physical properties of semiarid soil. Increased values of several parameters that serve as indicators of general microbiological activity, such as, basal respiration, adenosine triphosphate (ATP) or dehydrogenase activity;microbial population size (microbial biomass C), and extracellular hydrolase activity related to macronutrient cycles, such as, urease, β-glucosidase, and N-α-benzoyl-L-argininamide protease, were observed in the amended soils. The highest MSW doses showed the highest values in these hydrolase activities. The incorporation of municipal waste resulted in a more dense development of the plant cover, 50% greater in higher doses than in the control treatment, which generated a substantial increase in several C fractions. Total organic carbon reached 12 g kg^-1 soil with the highest MSW doses, compared to 4.30 g kg^-1 soil in the control treatment. The physical properties of the soil were also improved, showing greater percentage of stable aggregates and water holding capacity. Positive correlation coefficients between C fractions and parameters related to microbial activity and aggregate stability were observed. Although these improvements were greater in the soils receiving the highest doses of organic amendment, the increases were not proportional to the amount added, demonstrating the existence of a threshold, above which an increase in the amount of organic matter added is not reflected in an increase in the soil's physical, biochemical, and microbiological properties. However, the addition of municipal solid wastes proved its suitability for improving soil quality, thereby indicating the potential of such an amendment, to prevent desertification in Mediterranean areas such as those studied.     

Effects of a vermicompost composted with beet vinasse on soil properties, soil losses and soil restoration

The use of organic rich wastes instead or as a complement of mineral fertilizers is considered a good environmental practice, provided that the organic wastes are not severely polluted (e.g. occurrence of heavy metals, organic pollutants and/or pathogens). However, the effect of a particular organic waste on soil properties, soil loss and soil restoration depends on its chemical composition. In particular, the application of fresh beet vinasse showed a detrimental impact on the soil's physical, chemical and biological properties, increasing soil loss and decreasing plant cover, probably because it contains high quantities of monovalent cations, such as Na⁺, which destabilize the soil structure. The main objective of this work was to study the effect of beet vinasse co-composted with a vermicompost (constituted by green forages) at rates of 5 and 10 t kg organic matter ha^− 1, on physical (structural stability and bulk density), chemical (exchangeable sodium percentage) and biological (soil microbial biomass-C, soil respiration and soil enzymatic activities) properties of soils and, consequently, how its application may contribute to soil loss and soil restoration. The experiment was carried out for three years on a Xerollic Calciorthid located near Seville (Guadalquivir Valley, Andalusia, Spain). The co-composting of beet vinasse and green waste vermicompost had a positive effect on the soil's physical, chemical and biological properties, leading to a decrease in soil loss (31.2% compared with unamended soil) and an increase in plant cover (68.7% compared with unamended soil). These results suggest that the co-composting of beet vinasse with vermicomposts protects the soil and contributes to its restoration, thus representing a good strategy for recovering semiarid areas.     

Modification of soil enzyme activities as a consequence of replacing meadows by pine plantations under temperate climate

Changes in land use frequently modify the capacity of ecosystems to provide services. The purpose of this study was to investigate the effects of a specific land-use change, i.e. from meadows to pine plantations under temperate climate, on soil enzyme activities. To this aim, the variation of five key soil enzyme activities (dehydrogenase, β-glucosidase, arylsulphatase, acid phosphatase and urease) was evaluated in different sites located in the Urdaibai Reserve of the Biosphere (northern Spain). Lower values of dehydrogenase [effect size, computed as 100 × (1 − mean value from pine plantations/mean value from meadows), was 82.9%], β-glucosidase (52.9%) and urease (52.5%) activity were observed in soils from pine plantations versus meadows. Acid phosphatase and arylsulphatase activity showed a pattern of variation that was not dependent on land-use. The largest variation in enzyme activity values was due to changes at the small scale, not between the studied sites, an encouraging finding for the suitability of enzyme activities as bioindicators of the impact of land-use changes on soil functioning. Our results suggest that nutrient cycling (as reflected by the values of soil enzyme activities) might have been modified as a consequence of replacing meadows by pine plantations.     

Improvements in soil quality and performance of mycorrhizal Cistus albidus L. seedlings resulting from addition of microbially treated sugar beet residue to a degraded semiarid Mediterranean soil

Abstract. A field experiment was undertaken to assess the effectiveness of a combined treatment, involving addition of Aspergillus niger -treated sugar beet (SB) residue in the presence of rock phosphate and mycorrhizal inoculation of seedlings with Pisolithus tinctorius . The aim was to improve the physical, chemical, biochemical and biological properties of a degraded semiarid Mediterranean soil. Short-term effects of such improvements on the establishment of Cistus albidus L. seedlings were evaluated. Eight months after planting, macronutrients (NPK), total carbohydrates, water-soluble C, water-soluble carbohydrates, microbial biomass C and enzyme activities (dehydrogenase, urease, protease, acid phosphatase and β-glucosidase) measured in the rhizosphere soil of C. albidus were increased greatly by addition of fermented SB residue. Soil structural stability improved only with the fermented SB addition (about 79% higher in the amended soils than in the non-amended soils). The mycorrhizal inoculation was the most effective treatment in improving the growth of C. albidus plants, but only slightly improved soil quality. Growth of inoculated plants was about 33% greater than plants grown in the amended soil and about 131% greater than control plants. The combined benefit of mycorrhizal inoculation of seedlings and addition of fermented SB residue to soil on plant growth was similar to that of the treatments applied individually.     

长期施用畜禽粪便对土壤生物化学质量指标的影响

采用两种母质发育的,长期施用畜禽粪便和化肥的稻麦轮作土壤作为供试土壤,探讨了施用畜禽粪便对土壤微生物组成、微生物生物量及活性、土壤酶活性等生物化学质量指标的影响。研究结果显示,与施用化肥比较,长期施用畜禽粪便显著提高了土壤细菌和放线菌数量(+72%和+132%)、土壤微生物生物量碳、氮(+89%和+74%)、土壤基础呼吸速率和微生物商(+49%和+45%),但降低了土壤真菌的数量(-38%)。土壤脲酶和转化酶活性也表现为长期施用畜禽粪便土壤高于施用化肥土壤。由于受土壤pH值强烈影响,土壤微生物代谢商(qCO2)和土壤磷酸酶活性没有表现出明显的变化规律。回归分析结果显示,长期施用畜禽粪便改变土壤活性有机碳含量和理化性质是导致土壤生物化学质量指标变化的主要原因。     

Tebuconazole application decreases soil microbial biomass and activity

A short-term mesocosm experiment was conducted to ascertain the impact of tebuconazole on soil microbial communities. Tebuconazole was applied to soil samples with no previous pesticide history at three rates: 5, 50 and 500 mg kg⁻¹ DW soil. Soil sampling was carried out after 0, 7, 30, 60 and 90 days of incubation to determine tebuconazole concentration and microbial properties with potential as bioindicators of soil health [i.e., basal respiration, substrate-induced respiration, microbial biomass C, enzyme activities (urease, arylsulfatase, β-glucosidase, alkaline phosphatase, dehydrogenase), nitrification rate, and functional community profiling]. Tebuconazole degradation was accurately described by a bi-exponential model (degradation half-lives varied from 9 to 263 days depending on the concentration tested). Basal respiration, substrate-induced respiration, microbial biomass C and enzyme activities were inhibited by tebuconazole. Nitrification rate was also inhibited but only during the first 30 days. Different functional community profiles were observed depending on the tebuconazole concentration used. It was concluded that tebuconazole application decreases soil microbial biomass and activity.     

Early impacts of cotton and peanut cropping systems on selected soil chemical,physical, microbiological and biochemical properties

This study investigated the impacts of cropping systems of cotton (Gossypium hirsutum L.; Ct) and peanut (Arachis hypogaea L.; Pt) on a Brownfield fine sandy soil (Loamy, mixed, superactive, thermic Arenic Aridic Paleustalfs) in west Texas, United States. Samples (0–12 cm) were taken 2 and 3 years after establishment of the plots from PtPtPt, CtCtPt and PtCtCt in March, June and September 2002, and in March 2003. Soil total N and aggregate stability were generally not different among the cropping systems. The pH of the soils was >8.0. Continuous peanut increased soil organic C, microbial biomass C (C_mic) and the activities of -glucosidase, -glucosaminidase, acid phosphatase, alkaline phosphatase, phosphodiesterase and arylsulfatase compared to the peanut-cotton rotations. The arylsulfatase activity of the fumigated field-moist soil and that resulting from the difference of the fumigated minus non-fumigated soil were greater in PtPtPt, but arylsulfatase activity of non-fumigated soil was unaffected by the cropping systems. Soil C_mic showed a different seasonal variation to enzyme activities during the study. Enzyme activities:microbial biomass ratios indicated that the microbial biomass may not have produced significant amounts of enzymes or that newly released enzymes did not become stabilized in the soil (i.e., due to its low clay and organic matter contents). Fungal (18:26c and 18:19c) and bacterial (15:0, a15:0, and a17:0) FAMEs were higher in PtPtPt than in CtCtPt or PtCtCt cropping systems. Our results suggest that the quality or quantity of residues returned to the soil under a peanut and cotton rotation did not impact the properties of this sandy soil after the first 3 years of this study.     

Effects of municipal solid waste compost amendments on soil enzyme activities and bacterial genetic diversity

Municipal solid waste (MSW) composts have been used to maintain the long-term productivity of agroecosystems and to protect the soil environment from overcropping, changes in climatic conditions and inadequate management; they also have the additional benefit of reducing waste disposal costs. Since MSW may contain heavy metals and other toxic compounds, amendments cannot only influence soil fertility, but may also affect the composition and activity of soil microorganisms. The effects of MSW compost and mineral N amendments in a 6-year field trial on some physical-chemical properties, enzyme activities and bacterial genetic diversity of cropped plots (Beta vulgaris-Triticum turgidum rotation) and uncropped plots were investigated. The compost was added at the recommended and twice the recommended dosage (12, 24 t ha⁻¹). Amendments of cropped plots with MSW compost increased the contents of organic C from 13.3 to 15.0 g kg⁻¹ soil and total N from 1.55 to 1.65 g kg⁻¹ soil. There were significant increases in dehydrogenase (9.6%), β-glucosidase (13.5%), urease (15.4%), nitrate reductase (21.4%) and phosphatase (9.7%) activities. A significant reduction in protease activity (from 3.6 to 2.8 U g⁻¹ soil) was measured when a double dose of compost was added to the cropped plots. No dosage effect was detected for the other enzymes. Changes in the microbial community, as a consequence of MSW amendment, were minimal as determined using denaturing gradient gel electrophoresis, rDNA internal spacer analysis and amplified ribosomal DNA restriction analysis of bacteria, archaea, actinomycetes, and ammonia oxidizers. This indicates that there was no significant variation in the overall bacterial communities nor in selected taxonomic groups deemed to be essential for soil fertility.     

Microbiological degradation index of soils in a semiarid climate

Soil degradation and desertification affect many areas of the planet. One such area is the Mediterranean region of SE Spain, where the climatological and lithological conditions, together with the relief of the landscape and anthropological activity, including agricultural abandonment, are responsible for increasing desertification. It is therefore considered to be of extreme importance to be able to measure soil degradation quantitatively. The aim of this study was to make a microbiological and biochemical characterisation of different soil catenas in SE Spain, including in a wide range of plant cover densities in an attempt to assess the suitability of the parameters measured to reflect the state of soil degradation and the possibility of using the parameters to elaborate a microbiological degradation index (MDI) valid for use in semiarid climates. For this, several indices related with the organic matter content (total organic carbon, TOC, water-soluble carbon, WSC, and water-soluble carbohydrates, WSCh), with the size of microbial populations (microbial biomass carbon, MBC) and related activity (respiration and enzymatic activities) were determined in the soils of three different catenas in different seasons of the year. The values of these parameters were seen to be closely related with the degree of vegetal cover, forest soils with a high cover value showing the highest indices. There was a highly significant positive correlation (p<0.01) between the TOC and WSC content, and other parameters such as MBC, ATP, dehydrogenase activity and the activity of different hydrolases (urease, protease, phosphatase and β-glucosidase). The results show that the parameters analysed are a good reflection of a soil's microbiological quality since the soils with the worst characteristics (saline and with low organic matter and nutrient content) showed the lowest values. The study provides a soil degradation index based on its microbiological properties: MDI. This index is a function of the following five parameters, which showed the greatest weight in the factorial analysis made with all the parameters analysed: dehydrogenase activity, WSCh, urease activity, WSC and respiration.     

Do general spatial relationships for microbial biomass and soil enzyme activities exist in temperate grassland soils?

In heterogeneous environments such as soil it is imperative to understand the spatial relationships between microbial communities, microbial functioning and microbial habitats in order to predict microbial services in managed grasslands. Grassland land-use intensity has been shown to affect the spatial distribution of soil microorganisms, but so far it is unknown whether this is transferable from one geographic region to another. This study evaluated the spatial distribution of soil microbial biomass and enzyme activities involved in C-, N- and P-cycling, together with physico-chemical soil properties in 18 grassland sites differing in their land-use intensity in two geographic regions: the Hainich National Park in the middle of Germany and the Swabian Alb in south-west Germany. Enzyme activities associated with the C- and N-cycles, namely β-glucosidase, xylosidase and chitinase, organic carbon (C_org), total nitrogen (N_t), extractable organic carbon, and mineral nitrogen (N_min) were higher in the Swabian Alb (Leptosols) than in the Hainich National Park (primarily Stagnosols). There was a negative relationship between bulk density and soil properties such as microbial biomass (C_mic, N_mic), urease, C_org, and N_t. The drivers (local abiotic soil properties, spatial separation) of the enzyme profiles (β-glucosidase, chitinase, xylosidase, phosphatase, and urease) were determined through a spatial analysis of the within site variation of enzyme profiles and abiotic properties, using the Procrustes rotation test. The test revealed that physical and chemical properties showed more spatial pattern than the enzyme profiles. β-glucosidase, chitinase, xylosidase, phosphatase, and urease activities were related to local abiotic soil properties, but showed little spatial correlation. Semivariogram modeling revealed that the ranges of spatial autocorrelation of all measured variables were site specific and not related to region or to land-use intensity. Nevertheless, land-use intensity changed the occurrence of spatial patterns measurable at the plot scale: increasing land-use intensity led to an increase in detectable spatial patterns for abiotic soil properties on Leptosols. The conclusion of this study is that microbial biomass and functions in grassland soils do not follow general spatial distribution patterns, but that the spatial distribution is site-specific and mainly related to the abiotic properties of the soils.     

黄土高原旱地轮作与施肥长期定位试验研究 Ⅱ.土壤酶活性与土壤肥力

本文分析了长期试验土壤酶活性与土壤有机C、全N、有效P含量、主要微生物类群之间的关系。相关分析表明,土壤脲酶、碱性磷酸酶、蛋白酶活性随土壤有机C含量的增加而增加,蔗糖酶、过氧化氢酶活性与有机C之间的关系因施肥种类及种植方式的不同而不同;微生物数量仅真菌与脲酶、蛋白酶活性之间的相关性达到显著水平。除过氧化氢酶外,其它4种酶的活性均与当年种植冬小麦处理的产量存在显著相关关系。利用主成分分析与通径分析揭示了土壤酶活性与养分之间的内在关系及酶活性对土壤养分的影响。根据主成分分析结果,旱地土壤肥力状况用脲酶、碱性磷酸酶、蛋白酶活性作为综合评价指标优于过氧化氢酶与蔗糖酶。     

Influence of inorganic fertilizers and organic amendments on soil organic matter and soil microbial properties under tropical conditions

 Soil organic matter level, mineralizable C and N, microbial biomass C and dehydrogenase, urease and alkaline phosphatase activities were studied in soils from a field experiment under a pearl millet-wheat cropping sequence receiving inorganic fertilizers and a combination of inorganic fertilizers and organic amendments for the last 11 years. The amounts of soil organic matter and mineralizable C and N increased with the application of inorganic fertilizers. However, there were greater increases of these parameters when farmyard manure, wheat straw or Sesbania bispinosa green manure was applied along with inorganic fertilizers. Microbial biomass C increased from 147 mg kg^–1 soil in unfertilized soil to 423 mg kg^–1 soil in soil amended with wheat straw and inorganic fertilizers. The urease and alkaline phosphatase activities of soils increased significantly with a combination of inorganic fertilizers and organic amendments. The results indicate that soil organic matter level and soil microbial activities, vital for the nutrient turnover and long-term productivity of the soil, are enhanced by use of organic amendments along with inorganic fertilizers. Received: 6 May 1998     

Long-term effects of farmyard manure and sewage sludge on some soil biochemical characteristics

 Changes in some soil biochemical properties were investigated following repeated applications of aerobically digested sewage sludge (SS) under field conditions over 12 years, and compared with those of an adjacent soil cultivated and amended with 5 t ha^–1 year^–1 (dry weight) farmyard manure (FYM) for at least 40 years, as well as with those of an adjacent uncultivated soil, in order to ascertain changes in soil quality. A short-term aerobic incubation was used to determine the potential of the samples to mineralize the organic C supplied. Results indicated that cultivation caused a reduction in total, humified and potentially mineralizable organic C, total N, light-fraction (LF) C, total and water-soluble carbohydrates, phenolic compounds, cation-exchange capacity (CEC), microbial biomass C, specific respiration, hydrolytic and urease activities, and an increase in the heavy metal content. Total and water-soluble carbohydrates and phenolic compounds expressed as a percentage of total organic C (TOC) were similar in the differently managed plots. Of the two amendments, FYM treatments showed higher amounts of TOC and N, LF-C, total and water-soluble carbohydrates, phenolic substances, CEC, specific respiration of biomass, hydrolytic and urease activities, similar amounts and characteristics of humified organic matter and lower concentrations of Cu, Zn and Cr. Both FYM and SS were inadequate treatments for the restoration of soil organic matter lost as a consequence of cultivation. Received: 20 October 1998