土壤肥力，微生物及植物之间有密切的互作关系。微生物在根际生产植物生长调节物质及养分，植物也根据所遇到微生物的不同而调整自己的防御和生长方式。因此，农业生产中微生物与植物的互作机制的解析利用这一问题一直是人们关注的热点。植物生长所需养分中氮是最主要的元素之一，自然生态系统几乎都依靠固氮微生物获取氮元素。其中自生固氮菌是土壤环境里能够独立固氮的细菌。活性化自生固氮菌。因此，提高耕地土壤氮的含量这一问题也是当今微生物研究的热点之一。本项目拟使用耕地不同的管理措施解析半干旱地土壤总细菌和自生固氮菌多样性和活性的时间，空间动态，探讨耕地管理措施，作物生长及土壤微生物之间的互作机制。为半干旱地的合理农业生产措施提供科学支撑。

There are close interactions among soil fertility, microorganisms and plants. Microorganisms could produce plant growth-regulating substances and supply nutrients in plant rhizosphere; moreover, plants could adjust their defense and growth according to the type of microorganisms. Thus, it has been a focus of attention that how to analyze and exploit the interaction mechanisms between microbes and plants in agricultural production. Nitrogen is one of the most important nutrient elements in plant growth. Plants obtain nitrogen relying mainly on the nitrogen-fixing microbes in natural ecosystems. Among them, the free-living nitrogen fixing bacteria can independently fix nitrogen in soil. It is also one of the hot spot in microbial research that how to activate the free-living nitrogen fixing bacteria, and thus enhance the nitrogen content of arable soil. The project focuses on analyzing the temporal and spatial dynamics of the diversity and activity between the total soil bacteria and the free-living nitrogen fixing bacteria in semi-arid land; and investigating the arable land management measures as well as the interaction mechanism between crop growth and soil microorganisms through the use of the different land management measures. The project could provide the scientific support for the reasonable agricultural production measures in the semi-arid land.