秸秆覆盖免耕土壤微生物生物量与养分转化的研究

 多年连续秸秆覆盖免耕，0-20cm土层土壤有机质、全氮、全磷、有效氮、有效磷含量和土壤蔗糖酶、磷酸酶活性明显提高；免耕能提高表层土壤微生物生物量，0-7.5cm土层比翻耕处理年平均增高51.7%。翻耕能增加土壤活跃微生物生物量，0-30cm土层翻耕土壤活跃微生物生物量比免耕高25.3%。0-30cm土层微生物对养分的固结量多于作物年吸收量，土壤微生物生物量在春季和秋季即冬小麦生长苗期增大，固结土壤养分，而在夏玉米生长时期的夏季降低，被矿化释放养分，所以微生物对土壤养分转化具有重要的调控作用。

THE RELATIONSHIP BETWEEN SOIL MICROBIAL BIOMASS AND THE TRANSFORMATION OF PLANT NUTRIENTS IN STRAW MULCHED NO-TILLAGE SOILS

Arable soil that have been no-tilled and covered with crop residues for several years developes anorganic matter,plant nutrients and microbial activity redistribution with a large content near the soil surface and decrease with depth.The concentrations of organic matter,total nitrogen and phosphorus are all remarkably increased in no-tilled soils and the activity of soil enzymes are higher in no-tillage soils than that in plowed soils.No-tillage leads to an increase in microbial biomass near the soil surface,in the depth of 0-7.5cw microbial biomass was 51.7% higher than that in plowed soils.The higher levels of microbial biomass occur in spring and autumn while wheat is in seedling and not able to absorb much nutrients from soil.In this period, microbial biomass begins to accumulate and conserve nutrients in a biologically active form. In summer,when crop growth and development is rapid, microbial biomass declines as nutrients mineralization increases to promote crop growth. The average amount of untrients immobilized by microbes in 0-30cm soil layar is slightly more than that of the annual uptake of crops;on the other hand, no-tillage makes biomass largely dormant,in the depth of 0-30cm soil,active microbial bionmass in plowed soil is 25.3% greater than that in no-tillage soil.