以少免耕及秸秆覆盖为核心的保护性耕作措施有利于建立健康的土壤体系，是水稻生产可持续发展的重要举措及方向。然而，保护性耕作不合理使用常导致温室气体排放增加、氮肥利用率下降、水稻产量减少等问题。为了合理配置保护性耕作措施，必须结合氮肥使用，以氮调碳，提高土壤微生物多样性，通过碳氮耦合，激发促进氮的生物小循环，控制氮的开放性大循环，实现增碳保氮，其关键是要探明影响碳、氮耦合循环的生物驱动机制。本项目拟采取大田试验与同位素示踪试验结合土壤微生物生物技术，以传统翻耕施肥为对照，设置免耕、秸秆还田与优化氮肥施用等处理，研究保护性耕作措施下稻田土壤碳、氮库的动态变化特征及其转化的主要过程，揭示碳氮转化相关的土壤微生物群落结构、功能与活性，从而探明土壤微生物代谢活动对土壤碳氮转化相互影响的机制，并定量评估保护性耕作措施下碳氮循环的生产和生态效应。为水稻生产减排、增汇、减氮、增产提供理论依据。

Conservational tillage practices construct healthy soil systems through reducedand no-tillage and straw returning, which serve as important measures for sustainable development of rice production. Recently, incorrect application of conservational tillage practices resulted in decrease in nitrogen use efficicency, and thereby rice yields. However, microbial effects on nitrogen cycles under conservational tillage practices remain unclear. So, this project hypothesizes that correct application of conservational tillage practice can alter soil C/N ratio, thus improving biological nitrogen cycles, reducing nitrogen loss and increasing rice yield. Field and pot expriments are conducted to study dynamic changes in soil carbon and nitrogen pool under conservational tillage practices, to discuss the effects of improved nitrogen fertilizatioin on key processes of nitrogen cycles, to reveal changes in microbial composition, function and activity related to nitrogen cycles, and explore effects of microorganism on soil nitrogen cycles. This study also investigates ecological effects of nitrogen cycles under improved conservational tillage practices. The results will provide theoretical basis about sustainable production of rice.