有机和常规生产模式下菜田土壤酶活性差异研究

Soil enzyme activity under organic versus conventional vegetable production systems

通过对露地及温室环境下有机和常规蔬菜栽培土壤采样,测定分析了5种参与土壤碳氮循环的酶活性,及其与土壤相关理化性质之间的关系。结果显示:温室及露地土壤EC值在有机生产中相应低于常规生产12%和16%;有机生产土壤微生物碳氮含量显著高于常规生产;不同生产模式下土壤酶活性差异显著,有机生产土壤中的蛋白酶、脲酶、脱氢酶、β-葡糖苷酶活性高于常规生产,而硝酸还原酶活性较常规生产低;有机与常规栽培对蛋白酶活性影响极显著(P=0.006 8),对脲酶活性影响程度达显著水平(P=0.012 4)。除脱氢酶以外,不同栽培模式环境对土壤中另外4种酶活性均有显著影响,温室栽培环境中的蛋白酶、脲酶和硝酸还原酶活性高于露地。除硝酸还原酶外,其他4种酶活性与可溶性全氮、微生物碳、微生物氮相关系数达到显著水平。分析表明,土壤酶活性受到栽培方式以及环境的影响,并且有机生产能够提高参与土壤碳氮循环的酶活性。土壤蛋白酶、脲酶、脱氢酶和β-葡糖苷酶活性能够作为表征土壤碳氮循环以及微生物活性的指标。

There has been a growing trend in using soil enzymes as indicators for changes in soil quality under different management practices.Although literature on this subject has tremendously grown in the last 10 years,most of the studies have focused on cultivated fields.However,research on cultivated vegetable soils also has significant implications.Experiments were conducted at two close-by fields（one under organic farming and the other under conventional farming） in Shanghai to investigate the influence of different horticultural farm management practices on soil enzyme activities.Four combinations of field type and management system-organic management in greenhouse（GO）,conventional management in greenhouse（GC）,organic management in open-field（LO） and conventional management in open-field（LC） conditions-were evaluated.Soil sampled at the 0-20 cm depth were analyzed using the traditional soil analysis method.Furthermore,proteinase,urease,dehydrogenase,β-glucosidase and nitrate reductase activities were determined.The results presented here fostered an in-depth understanding of the impacts of management practices on soil enzyme activities.Soil electrical conductivity（EC） under organic managements was less than that under conventional management by averages of 12% and 16% in greenhouse and open-field conditions,respectively.The levels of microbial biomass C and N under organic managements were higher than those under conventional managements.Significant differences were noted in proteinase and prease activities among the different management practices.Proteinase,urease,dehydrogenase and β-glucosidase activities were comparatively high under organic management,while nitrate reductase activity was low.Management practices significantly affected proteinase and urease activities with P values of 0.006 8 and 0.012 4 respectively.Environmental conditions of cultivation significantly influenced proteinase,urease,β-glucosidase and nitrate reductase activities.Enzyme activities were higher in organic managements under greenhouse conditions than in other treatments.Analysis showed that proteinase,urease,dehydrogenase and β-glucosidase activities were closely correlated（at significant levels） with total dissolved nitrogen,microbial biomass C and microbial biomass N.In summary,organic systems significantly improved soil microbial characteristics and increased soil organic C,which in turn enhanced soil enzyme activities.Moreover,proteinase,urease,dehydrogenase and β-glucosidase activities were suitable indicators for soil fertility.Further studies that focus on determining the relationship between soil microbial diversity and specific enzyme activities under different management systems using the DGGE（denaturing gradient gel electrophoresis） technique were therefore recommended.