Effects of consecutive turnover of green manures on soil microbial biomass and enzyme activity

A consecutive 3-year field experiment was conducted to study the effects of incorporation green manure on soil microbial biomass carbon, microbial biomass nitrogen and soil enzyme activities. The results showed that incorporation green manure could increase soil microbial biomass C, N and the activities of soil urease, acid phosphatase（ACP）, sucrase, and catalase with the increasing of the returning age. Compared with the control, the contents of soil microbial biomass C and N were increased by 31.0%-67.1% and 23.0%-145.1%, and the activities of soil urease, ACP, invertase and catalase by 34.4%-51.9%, 11.0%-18.6 %, 58.0%-172.7%, and 24.0%-50.0% after three years' consecutive turnover of green manure, respectively, suggesting that the turnover of organic matter was facilitated and more nutrients were released to meet the demanding of crop growth. The dynamical changes of soil microbial biomass C，N and the enzyme activity within tobacco development period showed that the maximum of microbial biomass C and N was observed at the rosett stage, while the peak of soil enzyme activities was appeared at the busy stage of flue-cured tobacco. Compared with the control, the maximum of soil biomass C, N increased 67.1% and 60.7% after tree years' consective turnover of green manure, respectively. The peak of soil urease, ACP, catalase activity increased 51.9%，14.2%，30.62%，respectively. Our results proved that incorporation green manure had a positive effect on soil fertility, microbial biomass C and N, and also indicated that the enzyme activities might be used as biological indices for soil quality due to their high sensitivity to soil fertility change.