豆科与禾本科间套作是提高资源利用率与生物固氮的有效途径，但其豆科固氮的生理生化机制尚不明确。本研究针对玉米/大豆套作的养分高效利用问题，先前研究发现，玉米/大豆套作可有效提高作物氮肥利用率与根瘤固氮能力，根瘤质量与固氮时间是影响其高效固氮的重要因素。在此基础上，本研究拟通过环境监测、酶活检测和qPCR等方法，对根系分泌物组分与根瘤菌多样性差异、根瘤形态结构与固氮生理参数、根区土壤环境与理化性质的动态变化进行深入研究，检测根瘤中活性氮与活性氧的含量以及NO清除剂（黄素血红蛋白）、抗氧化酶（SOD、CAT）与蛋白质降解酶（半胱氨酸蛋白酶）的含量、活性及其编码基因的表达差异，进一步阐明玉米/大豆套作下大豆根区土壤环境、根系分泌物变化与根瘤形成及衰老的关系，揭示根瘤高效固氮的生理生化机制。这将有助于完善禾豆间套作的氮高效利用理论，为间套作减肥增效技术研发提供理论依据。

It is well know that nodule nitrogen fixation is an effective way for crops to utilize the nitrogen fertilizer in legume-cereal intercropping system. However, the mechanisms involve physiology and biochemistry are still unclear. Previously, we found the nitrogen utilization efficiency was significant increase in maize-soybean relay intercropping. Together, a important factors which impacts nitrogen fixation is the quality and nodule nitrogen fixation time of nodule. Here, we will use methods including environmental monitoring, enzyme activity detection and quantitative polymerase chain reaction (q-PCR) to research nodule nitrogen fixation under the different root interaction strength of maize and soybean. We will to test the root exudates component and the rhizobium diversity, and to define the parameters of nodules physiological and morphology. In addition,we are also to determine the reactive nitrogen specis(RNS), reactive oxygen species(ROS), NO scavenger (flavohaemolobin), superoxide dismutase (SOD) , catalase (CAT) and activity and dynamic variations of encoding of proteolytic enzymes in this research. Through the research, we hope to clarify the relationships between the soil environment and nodule senescence, and root exudates and nodule formation, and reveal the physiology and biochemistry mechanism involves nodule nitrogen fixationthe in maize-soybean relay intercopping system as well as offers opportunities for further utilize nitrogen efficiently. In addition, this study will provide theoretical basis to technical development for reduction of excessive nitrogen applications in agriculture.