Variation of Soil Enzymes Activity and Relevant Nutrients at Different Years of Soybean(Glycine max L.)Rotation,Alternate and Continuous Cropping

In this paper,soil samples were collected from soybean rotation and continuous cropping fields for different years in the Hailun Agricultural Ecology Station of Chinese Academy of Sciences to study the variation of soil enzymes activity,nutrients,soil C and N contents and their relationship.The results showed that there was a great variation of soil enzymes activity,available nutrients and soil C and N contents,compared with soybean rotation,soil enzymes activity all decreased in alternate and continuous cropping,urease,invertase and phosphatase activity in continuous cropping for two years were decreased most than others,decreased by 29.6%,51.0% and 41.9%,respectively.Moreover,soil C,N and available N,P and K decreased most in continuous cropping for 2 years than others,decreased by 18.0%,35.3% and 40.4%,53.6%,41.3%,respectively.Soil C,N and different available nutrients contents reclaimed in an extent with continuous cropping years,however,long-term continuous cropping of soybean,above components showed a declined trend.There was a significantly positive correlation between urease,invertase,phosphatase and soil C,N,available N,P and K.Therefore,soil enzymes activity and available nutrients contents decreased in continuous cropping soils of soybean were important causes resulting in product decreasing of soybean in continuous cropping.