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1.
The response of a fresh, agricultural soil when contaminated with pentachlorophenol (PCP) and supplemented with compost (C) or dissolved organic matter (DOM) was studied in the laboratory. The concentration of PCP and the changes in various functionally related properties (i.e. microbial biomass, basal respiration, soil hydrolase and oxidoreductase activity) were measured over 150 d. Variations in the main physical and chemical properties of the soils were also monitored. Two different doses of compost (C1 = 0.27% and C2 = 0.83%, corresponding to 10 and 30 t ha−1, respectively) or DOM (D1 = 0.07% and D2 = 0.2%) equivalent to the carbon content of the two compost doses C1 and C2 were used and the following five systems were investigated: soil (S), soil–compost (S-C1 and S-C2) and soil–DOM (S-D1 and S-D2). PCP concentrations declined progressively and significantly with time. This effect was most pronounced for the soils amended with the lower compost dose C1 (S-C1) and with the two DOM (S-D1 and S-D2) amounts. Significantly reduced amounts of PCP were extracted after its 500-d residence in the various systems. Higher amounts of the residual PCP were extracted from the humic acids (HA), fulvic acids (FA) and humin–mineral (HU) fractions of the 500 d aged samples than from the same unfractionated samples, indicating that the residual PCP preferentially accumulated in the organic fractions of soil. The soil showed an endogenous microbial activity as indicated by basal respiration, microbial biomass and all the enzymatic activities tested (dehydrogenase, glucosidase, phosphatase, arylsulphatase and urease). Addition of the PCP severely depressed some of the tested biochemical properties suggesting an inhibitory effect on microbial activity. Conversely, higher basal respiration, and similar β-glucosidase and phosphatase activities were measured in comparison with the controls. No significant effects were observed following the addition of two doses of the compost or the DOM. Fungal colonies belonging to the taxonomic group of Ascomycetes and identified as Byssochlamys fulva developed with time in all the PCP-contaminated samples. Growth of B. fulva in vitro in the presence of PCP showed that the isolate was tolerant to 12.5 and 25 mg l−1 PCP and degraded 20% of its initial concentration in 8 d. Overall, the results indicate that many complex processes occurred in the contaminated soil and combinations of these determined the response to PCP contamination. The sorption of PCP to the soil matrix (which increased with time) and its degradation/transformation by indigenous soil microbial activity were likely involved. Both the processes appeared to be favoured by the presence of dissolved organic matter.  相似文献   

2.
The effects of municipal food waste compost addition and mineral fertilization on selected soil microbiological activities were investigated during 3 years of reiterated treatments on two Mediterranean agricultural soils with different organic carbon content. Compost at 15, 30 and 45 t ha−1 (dry matter), mineral (NPK) fertilizers and combined fertilizers with 15 t ha−1 of compost plus two reduced doses of mineral N were applied to both soils. At both sites, organic amendment increased soil respiration, fluorescein diacetate hydrolysis, phosphatase and arylsulphatase activities. The differences in soil microbial activities among treatments, found after 3 years of repeated treatments, were attributable to the variations of soil organic C content and to the impact of soil tillage. Our results show that, in Mediterranean intensively cultivated agroecosystems, annual organic amendments improve the microbial activity of soil and produce cumulative effects, suggesting the usefulness of repeated high-rate compost applications.  相似文献   

3.
Although soil biochemical properties are considered to be good indicators of changes in soil quality, few studies have been made of the changes in biochemical properties brought about by anthropogenic disturbance of grassland ecosystems. In the present study, several biochemical properties were analysed in 31 grassland soils subjected to a high level of management, and the values obtained were compared with known values corresponding to native grasslands from the same region (Galicia, NW Spain). The 31 managed grasslands were divided into two groups (re-sown grasslands and improved grasslands) according to their management and past land use. The biochemical properties studied were: labile carbon, microbial biomass carbon, microbial respiration, metabolic quotient, net nitrogen mineralisation and the activities of dehydrogenase, catalase, phosphodiesterase, phosphomonoesterase, casein hydrolysing proteases, benzoyl arginamide (BAA)-hydrolysing proteases, urease, cellulase, ß-glucosidase, invertase and arylsulphatase. Managed grasslands exhibited lower values of soil biochemical properties than native grasslands. Three biochemical equilibrium equations were used to compare soil quality in managed and native grasslands. One of the equations did not show any significant difference between the groups of grassland soils considered. In contrast, two of the equations showed similar soil quality for improved and native grasslands, while re-sown grasslands exhibited a loss of soil quality when compared to native grassland soils.  相似文献   

4.
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.  相似文献   

5.
Response of soil microbial communities to compost amendments   总被引：1，自引：0，他引：1  
Soil organic matter is considered as a major component of soil quality because it contributes directly or indirectly to many physical, chemical and biological properties. Thus, soil amendment with composts is an agricultural practice commonly used to improve soil quality and also to manage organic wastes. We evaluated in laboratory scale experiments the response of the soilborne microflora to the newly created soil environments resulting from the addition of three different composts in two different agricultural soils under controlled conditions. At a global level, total microbial densities were determined by classical plate count methods and global microbial activities were assessed by measuring basal respiration and substrate induced respiration (SIR). Soil suppressiveness to Rhizoctonia solani diseases was measured through bioassays performed in greenhouses. At a community level, the modifications of the metabolic and molecular structures of bacterial and fungal communities were assessed. Bacterial community level physiological profiles (CLPP) were determined using Biolog™ GN microtiter plates. Bacterial and fungal community structures were investigated using terminal restriction fragment length polymorphism (T-RFLP) fingerprinting. Data sets were analyzed using analysis of variance and ordination methods of multivariate data. The impact of organic amendments on soil characteristics differed with the nature of the composts and the soil types. French and English spent mushroom composts altered all the biological parameters evaluated in the clayey soil and/or in the sandy silty clay soil, while green waste compost did not modify either bacterial and fungal densities, SIR values nor soil suppressiveness in any of the soils. The changes in bacterial T-RFLP fingerprints caused by compost amendments were not related to the changes in CLPP, suggesting the functional redundancy of soil microorganisms. Assessing the density, the activity and the structure of the soil microflora allowed us not only to detect the impact of compost amendment on soil microorganisms, but also to evaluate its effect at a functional level through the variation of soil disease suppressiveness. Differences in disease suppressiveness were related to differences in chemical composition, in availability of nutrients at short term and in microbial composition due to both incorporation and stimulation of microorganisms by the compost amendments.  相似文献   

6.

Purpose  

Persistent organic compounds exhibit declining extractability and bioavailability to microorganisms and other soil organisms with increasing contact time or ageing. Among the possible mechanisms are the association of organic compounds with natural organic matter. Ageing can reduce the negative effects that an organic pollutant may have on the biological, biochemical properties and phytotoxicity of the contaminated soil. The aim of the present work was to evaluate, under laboratory conditions, the response of an agricultural soil contaminated with phenanthrene (Phe) and subjected to 2-year ageing and the effects and potential remediation capabilities of compost and an effective Phe-degrading bacterial culture.  相似文献   

7.
Olive mill waste water (OMW), a by-product of the olive mill industry, is produced in large amounts in Mediterranean countries. Olive mill waste water contains a high organic load, substantial amounts of plant nutrients but also several compounds with recognized toxicity towards living organisms. Moreover, OMW may represent a low cost source of water. Thus, the use of OMW for soil fertigation is a valuable option for its disposal, provided that its impact on soil chemical and biochemical properties is established. Investigations were performed on the short-term influence of OMW on several chemical and biochemical properties of a soil from a continental semi-arid Mediterranean region (Morocco). The soil was amended with 0, 18 and 36 ml 100 g−1 soil of OMW (corresponding to a field rate of 0, 40 and 80 m3 ha−1, respectively) and changes in various functionally related properties such as microbial biomass, basal respiration, extractable C and N, and soil hydrolases and oxido-reductases activities were measured over time. The variations of the main physical and chemical properties as well as the residual phytotoxicity of OMW amended and non-amended soils as assessed by tomato seed germination tests were also monitored. Temporary and permanent changes in several chemical and biochemical soil properties occurred following OMW application, thus being these properties varied in sensitivity to the applied disturbance. A sudden increase of total organic C, extractable N and C, available P and extractable Mn and Fe contents were measured. Simultaneously, a rapid increase of soil respiration, dehydrogenase and urease activities and microbial biomass (at 14 day incubation) of OMW amended soils occurred. In contrast, the activities of phosphatase, β-glucosidase, nitrate reductase and diphenol oxidase decreased markedly. The soil became highly phytotoxic after OMW addition (large decline of soil germination capability), mainly at 80 m3 ha−1 OMW. After 42 days' incubation, however, a complete recovery of the soil germination capability and a residual phytotoxicity of about 30% were observed with 40 and 80 m3 ha−1 OMW, respectively. These findings indicate that the impact of OMW on soil properties was the result of opposite effects, depending on the relative amounts of beneficial and toxic organic and inorganic compounds present. The toxic compounds contained in OMW most likely counteracted the beneficial effect of organic substrates provided, which promoted the growth and activity of indigenous microorganisms.  相似文献   

8.
不同施肥管理措施对土壤碳含量及基础呼吸的影响   总被引：12，自引：0，他引：12       下载免费PDF全文
连续7年试验研究了施用15t/hm2和7.5t/hm2有机肥(包括EM堆肥、EM鸡粪肥和传统堆肥)、化肥和对照处理对土壤碳含量与基础呼吸的影响,结果表明:随有机肥施用量的提高,土壤可溶性碳、总有机碳、微生物生物量碳和土壤的基础呼吸随之增加。施用化肥可一定程度提高土壤可溶性碳、总有机碳、微生物生物量碳和土壤的基础呼吸。不同施肥措施对土壤有机碳、微生物生物量碳和土壤基础呼吸的影响趋势为EM堆肥处理>传统堆肥处理>化肥处理>对照,施肥对土壤微生物代谢商的影响趋势为EM堆肥处理<传统堆肥处理<化肥处理<对照。土壤微生物生物量碳与可溶性碳、总有机碳及土壤基础呼吸之间呈极显著正相关。土壤微生物代谢商与土壤可溶性碳、总有机碳、微生物生物量碳及基础呼吸之间呈极显著负相关。  相似文献   

9.
《Pedobiologia》2014,57(4-6):235-244
Vegetation type influences the rate of accumulation and mineralization of organic matter in forest soil, mainly through its effect on soil microorganisms. We investigated the relationships among forest types and microbial biomass C (MBC), basal respiration (RB), substrate-induced respiration (RS), N mineralization (Nmin), specific growth rate μ, microbial eco-physiology and activities of seven hydrolytic enzymes, in samples taken from 25 stands on acidic soils and one stand on limestone, covering typical types of coniferous and deciduous forests in Central Europe. Soils under deciduous trees were less acidic than soils of coniferous forests, which led to increased mineralizing activities RB and Nmin, and a higher proportion of active microbial biomass (RS/MBC) in the Of horizon. This resulted in more extractable organic C (0.5 M K2SO4) in soils of deciduous forests and a higher accumulation of soil organic matter (SOM) in coniferous forest soil. No effect of forest type on the microbial properties was detected in the Oh horizon and in the 0–10 cm layer. The microbial quotient (MBC/Corg), reflecting the quality of organic matter used for microbial growth, was higher in deciduous forests in all three layers. The metabolic quotient qCO2 (RB/MBC) and the specific growth rate μ, estimated using respiration growth curves, did not differ in soils of both forest types. Our results showed that the quality of SOM in coniferous forests supported microorganisms with higher activities of β-glucosidase, cellobiosidase and β-xylosidase, which suggested the key importance of fungi in these soils. Processes mediated by bacteria were probably more important in deciduous forest soils with higher activities of arylsulphatase and urease. The results from the stand on limestone showed that pH had a positive effect on microbial biomass and SOM mineralization.  相似文献   

10.
Soil organic carbon (SOC), microbial biomass carbon (MBC), their ratio (MBC/SOC) which is also known as microbial quotient, soil respiration, dehydrogenase and phosphatase activities were evaluated in a long-term (31 years) field experiment involving fertility treatments (manure and inorganic fertilizers) and a maize (Zea mays L.)-wheat (Triticum aestivum L.)-cowpea (Vigna unguiculata L.) rotation at the Indian Agricultural Research Institute near New Delhi, India. Applying farmyard manure (FYM) plus NPK fertilizer significantly increased SOC (4.5-7.5 g kg−1), microbial biomass (124-291 mg kg−1) and microbial quotient from 2.88 to 3.87. Soil respiration, dehydrogenase and phosphatase activities were also increased by FYM applications. The MBC response to FYM+100% NPK compared to 100% NPK (193 vs. 291 mg kg−1) was much greater than that for soil respiration (6.24 vs. 6.93 μl O2 g−1 h−1) indicating a considerable portion of MBC in FYM plots was inactive. Dehydrogenase activity increased slightly as NPK rates were increased from 50% to 100%, but excessive fertilization (150% NPK) decreased it. Acid phosphatase activity (31.1 vs. 51.8 μg PNP g−1 h−1) was much lower than alkali phosphatase activity (289 vs. 366 μg PNP g−1 h−1) in all treatments. Phosphatase activity was influenced more by season or crop (e.g. tilling wheat residue) than fertilizer treatment, although both MBC and phosphatase activity were increased with optimum or balanced fertilization. SOC, MBC, soil respiration and acid phosphatase activity in control (no NPK, no manure) treatment was lower than uncultivated reference soil, and soil respiration was limiting at N alone or NP alone treatments.  相似文献   

11.
The use of composts in agricultural soils is a widespread practice and the positive effects on soil and plants are known from numerous studies. However, there have been few attempts to compare the effects of different kinds of composts in one single study. The aim of this paper is to investigate to what extent and to which soil depth four major types of composts would affect the soil and its microbiota.In a crop-rotation field experiment, composts produced from (i) urban organic wastes, (ii) green wastes, (iii) manure and (iv) sewage sludge were applied at a rate equivalent to 175 kg N ha−1 yr−1 for 12 years. General (total organic C (Corg), total N (Nt), microbial biomass C (Cmic), and basal respiration), specific (enzyme activities related to C, N and P cycles), biochemical properties and bacterial genetic diversity (based on DGGE analysis of 16S rDNA) were analyzed at different depths (0-10, 10-20 and 20-30 cm).Compost treatment increased Corg at all depths from 11 g kg−1 for control soil to 16.7 g kg−1 for the case of sewage sludge compost. Total N increased with compost treatment at 0-10 cm and 10-20 cm depths, but not at 20-30 cm. Basal respiration and Cmic declined with depth, and the composts resulted in an increase of Cmic and basal respiration. Enzyme activities were different depend on the enzyme and among compost treatments, but in general, the enzyme activities were higher in the upper layers (0-10 and 10-20 cm) than in the 20-30 cm layer. Diversity of ammonia oxidizers and bacteria was lower in the control than in the compost soils. The type of compost had less influence on the composition of the microbial communities than did soil depth.Some of the properties were sensitive enough to distinguish between different compost, while others were not. This stresses the need of multi-parameter approaches when investigating treatment effects on the soil microbial community. In general, with respect to measures of activity, biomass and community diversity, differences down the soil profile were more pronounced than those due to the compost treatments.  相似文献   

12.
Biochemical characterization of urban soil profiles from Stuttgart, Germany   总被引：1，自引：0，他引：1  
The knowledge of biochemical properties of urban soils can help to understand nutrient cycling in urban areas and provide a database for urban soil management. Soil samples were taken from 10 soil profiles in the city of Stuttgart, Germany, differing in land use—from an essentially undisturbed garden area to highly disturbed high-density and railway areas. A variety of soil biotic (microbial biomass, enzyme activities) and abiotic properties (total organic C, elemental C, total N) were measured up to 1.9 m depth. Soil organic matter was frequently enriched in the subsoil. Microbial biomass in the top horizons ranged from 0.17 to 1.64 g C kg−1, and from 0.01 to 0.30 g N kg−1, respectively. The deepest soil horizon at 170-190 cm, however, contained 0.12 g C kg−1 and 0.05 kg N kg−1 in the microbial biomass. In general, arylsulphatase and urease activity decreased with depth but in three profiles potentially mineralizable N in the deepest horizons was higher than in soil layers directly overlying. In deeply modified urban soils, subsoil beside topsoil properties have to be included in the evaluation of soil quality. This knowledge is essential because consumption of natural soils for housing and traffic has to be reduced by promoting inner city densification.  相似文献   

13.
不同恢复方式下盐渍化弃耕地土壤生物学活性的变化   总被引：2，自引：0，他引：2  
以干旱区新疆玛纳斯河流域冲积扇缘定点定位试验地为研究对象, 研究灌溉处理、人工草地处理和补植处理对盐渍化弃耕地土壤微生物量、酶活性及土壤呼吸速率的影响。结果表明, 不同恢复方式均明显增加了土壤微生物数量和土壤微生物量碳、氮及土壤酶活性。不同处理土壤微生物量碳、氮分别比原始弃耕地高17.80%、26.38%、5.33%和7.89%、12.75%、21.93%; 不同处理土壤微生物数量分别是原始弃耕地的4.72倍、6.04倍和4.56倍; 不同处理土壤蔗糖酶活性分别比原始弃耕地高3.4倍、3.2倍和7.7倍, 多酚氧化酶活性比原始弃耕地高1.7倍、1.2倍和1.5倍, 脲酶活性比原始弃耕地高11.1%、52.3%和37.1%; 灌溉处理土壤过氧化氢酶活性最高, 是原始弃耕地的1.53倍, 土壤呼吸速率变化表现为人工草地处理>灌溉处理>补植处理>原始弃耕地, 其中, 人工草地处理土壤呼吸速率比弃耕地高52.25%。相关分析表明, 微生物量碳与微生物C/N和微生物数量之间均呈显著正相关关系(P<0.05); 土壤呼吸速率与土壤脲酶、微生物数量和微生物量碳的相关性达到显著水平(P<0.05), 与土壤微生物量氮呈负相关关系, 但相关性不显著; 土壤蔗糖酶与其他3种酶以及微生物量氮呈显著正相关关系, 土壤脲酶与微生物数量呈显著正相关关系, 多酚氧化酶与过氧化氢酶相关性达到显著水平(P<0.05)。本研究表明干旱区盐渍化弃耕地采用灌溉与人工草地处理有利于土壤养分积累, 可在一定程度上改善土壤质量。  相似文献   

14.
The release of CO2 by soil microorganisms after the addition of nitrogen and glucose in excess and calibration additions of phosphorus has successfully been used to assess microbial available P, assuming the native soil P pool is then limiting respiration. However, in P-fixing soils and soils with high P content, carbon can be exhausted before the available soil P pool. It is not possible to simply increase the amount of glucose as then the glucose concentration would be lethal for microorganisms. A modified method was tested where soil is mixed with perlite. It was hypothesised that perlite, having a high water holding capacity, would dilute the concentration of glucose, while maintaining the bioavailability of added nutrients, thus avoiding carbon limitation. Factorial combinations of amount of soil and perlite (both adjusted to −25 kPa water potential) were tested to examine if perlite as such had any effect on the respiration. Five tropical soil samples with a sharp gradient in P availability and one N-limited compost material were used. The method successfully reduced the risk of carbon limitation. Microbial indices, such as basal respiration, substrate-induced respiration and maximum P-limited respiration, were directly proportional to the amount of soil in the experiments but unrelated to the amount of perlite, showing that perlite did not affect microbial measurements.  相似文献   

15.
In vineyards, the long-term use of copper fungicides has increased soil Cu concentrations that can adversely affect the number and activities of soil microorganisms. To better understand this phenomenon and to ameliorate such harmful effects, an incubation experiment was carried out with a sandy loam and a sandy soil to which increasing rates of CuSO4 were added. By this treatment, the basal soil respiration (7-55%) and decomposition of added vine branches (46-86%) was inhibited. At the application rate of 500 mg Cu kg?1, soil microbial biomass-C was inhibited (7-66%) in the sandy soil and stimulated (2-10%) in the sandy loam soil. The specific respiration rate was a reliable indicator for Cu stress, and it increased with time and higher Cu concentrations before lime and compost applications. Total number of bacteria and streptomycetes were also strongly inhibited. Fungal population was significantly more tolerant to copper toxicity than the bacteria. A stimulation of fungal population at a dose of 500 mg Cu kg?1 in both soils was observed. A criterion such as “stimulation” lasting for more than 60 days can also be used as indication of Cu contamination of soils. The order of inhibition (on day 125) at a dose of 500 mg Cu kg?1 soil was as follows: A. sandy loam soil (pH> 7.0) — fungi < biomass-C < basal soil respiration < bacteria < streptomycetes; B. sandy soil (pH< 6.0) — fungi < basal soil respiration < biomass-C < bacteria < streptomycetes. The application of lime increased soil recovering ability at a moderate rate (for CO2 production – 22-70% and for biomass-C- 39-156%), but the combination of lime and compost significantly increased soil resiliency (for CO2 production- 16-518% and for biomass-C- 103-693%). The soil resiliency assessed by number of bacteria in compost treatments was 30-120% in sandy loam soil and 92-700% in the sandy soil. Compost and lime application increased the number of streptomycetes from 52 to 500% in sandy loam soil and from 100 to 700% in sandy loam soil. Fungal population was less increased in sandy soil as compared to sandy loam soil. The ecological dose higher than 5% inhibition of microbial processes and microorganisms appears to be suitable to assess Cu contamination of soils. CO2 production, biomass-C and specific respiration rate were less sensitive indicators as compared to streptomycetes and bacteria. It appears that compost application effectively promoted the recovery of soil microbial activity and soil fertility of Cu contaminated soils.  相似文献   

16.
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.  相似文献   

17.
The effects of crop residue management and fertilizer applications on the size and activity of the microbial community and the activity of exocellular enzymes involved in mineralization of C, N, P and S were examined on a long-term (60 years) field trial under sugarcane situated at Mount Edgecombe, South Africa. Treatments at the site included pre-harvest burning with harvest residues removed (B), burning with harvest residues (unburnt tops) left on the soil surface (Bt) and green cane harvesting with retention of a trash blanket (T). Plots were either fertilized annually with N, P and K or unfertilized. The size and activity of the microbial community and the activity of soil enzymes assayed increased with increasing inputs of crop residues (B < Bt < T) and this effect was evident to a depth of 30 cm. The metabolic quotient was decreased by inputs of both crop residues and fertilizers. Annual fertilizer additions did not affect basal respiration, increased fluorescein diacetate (FDA) hydrolysis rate and acid phosphatase, invertase and protease activities and decreased arginine ammonification rate and dehydrogenase, alkaline phosphatase, arylsulphatase and histidase activities. These effects were attributed to an interaction between the positive effect of fertilizer in increasing the size of the microbial biomass and the negative effect of fertilizer-N-induced soil acidification on microbial activity and on the activity of exocellular enzymes. Such results demonstrate the importance of using a range of measurements of microbial and enzyme activity when determining the effects of management on soil microbial and biochemical properties.  相似文献   

18.
The effects of tillage on the interaction between soil structure and microbial biomass vary spatially and temporally for different soil types and cropping systems. We assessed the relationship between soil structure induced by tillage and soil microbial activity at the level of soil aggregates. To this aim, organic C (OC), microbial biomass C (MBC) and soil respiration were measured in water-stable aggregates (WSA) of different sizes from a subtropical rice soil under two tillage systems: conventional tillage (CT) and a combination of ridge with no-tillage (RNT). Soil (0–20 cm) was fractionated into six different aggregate sizes (> 4.76, 4.76–2.0, 2.0–1.0, 1.0–0.25, 0.25–0.053, and < 0.053 mm in diameter). Soil OC, MBC, respiration rate, and metabolic quotient were heterogeneously distributed among soil aggregates while the patterns of aggregate-size distribution were similar among properties, regardless of tillage system. The content of OC within WSA followed the sequence: medium-aggregates (1.0–0.25 mm and 1.0–2.0 mm) > macro-aggregates (4.76–2.0 mm) > micro-aggregates (0.25–0.053 mm) > large aggregates (> 4.76 mm) > silt + clay fractions (< 0.053 mm). The highest levels of MBC were associated with the 1.0–2.0 mm aggregate size class. Significant differences in respiration rates were also observed among different sizes of WSA, and the highest respiration rate was associated with 1.0–2.0 mm aggregates. The Cmic/Corg was greatest for the large-macroaggregates regardless of tillage regimes. This ratio decreased with aggregate size to 1.0–0.25 mm. Soil metabolic quotient (qCO2) ranged from 3.6 to 17.7 mg CO2 g− 1 MBC h− 1. The distribution pattern of soil microbial biomass and activity was governed by aggregate size, whereas the tillage effect was not significant at the aggregate scale. Tillage regimes that contribute to greater aggregation, such as RNT, also improved soil microbial activity. Soil OC, MBC and respiration rate were at their highest levels for 1.0–2.0 mm aggregates, suggesting a higher biological activity at this aggregate size for the present ecosystem.  相似文献   

19.
The effectiveness of adding two organic wastes (cotton gin crushed compost, CGCC, and poultry manure, PM) to a saline soil (Salorthidic Fluvaquent) in dryland conditions near Seville (Guadalquivir Valley, Andalusia, Spain) was studied during a period of 5 years. Organic wastes were applied at rates of 5 and 10 t organic matter ha−1. One year after the assay began, spontaneous vegetation had appeared in the treated plots, particularly in that receiving a high PM dose. After 5 years the plant cover in this treated plot was around 80% (compared with the 8% of the control soil). The effect on the soils physical and chemical properties, soil microbial biomass, and six soil enzymatic activities (dehydrogenase, urease, protease, β-glucosidase, arylsulfatase, and phosphatase activities) were ascertained. Both added organic wastes had a positive effect on the physical, chemical and biological properties of the soil, although at the end of the experimental period, the soil physical properties, such as bulk density, increased more significantly in the CGCC-amended soils (23%) and the exchangeable sodium percentage (ESP) decreased more significantly in the CGCC-amended soils (50%) compared to the unamended soil. Water soluble carbohydrates and soil biochemical properties were higher in the PM-amended soils compared to the CGCC-amended soils (by 70% for water soluble carbohydrates, and by 34, 18, 37, 39, 40 and 30% for urease, protease, β-glucosidase, phosphatase, arylsulfatase and dehydrogenase activities, respectively). After 5 years, the percentage of plant cover was >50% in all treated plots and 8% in the control soil.  相似文献   

20.
Water availability strongly affects soil microbial activity and community composition. In a laboratory incubation we investigated the combined effect of soil moisture potential (−10 kPa, −135 kPa, and <−1500 kPa) and plant residue addition on soil enzyme activities (protease, β-glucosidase, β-glucosaminidase and exocellulase) and phospholipid fatty acid (PLFA) profiles. Soil respiration was positively correlated with soil moisture potential and significantly increased with the addition of residue. In the unamended soil, enzyme activities were little affected by soil moisture potential, nor did they change much over time. The addition of residue, however, significantly increased enzyme activity at each moisture level. Furthermore, all four enzyme activities were considerably higher in the amended dry soil than in amended samples with a higher moisture potential. In contrast, in the amended dry soil, respiration and microbial biomass were reduced compared to the amended samples with a higher moisture potential. The low microbial biomass in the amended dry soil was mainly due to a decrease in Gram-negative bacteria, while the fungal biomass reached similar levels at all water potentials. Therefore, shifts in microbial community composition alone cannot explain the increased enzyme activities in the dry soil. Other factors, such as increased fungal activity, stronger interactions between enzymes and soil particles due to thinner water films, may have contributed to the observed effects. Our results suggest that under dry conditions, potential enzyme activities may be decoupled from microbial biomass and respiration in the presence of substrates.  相似文献   

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