充分利用水分与氮素对作物生长和土壤质量的协同作用，是提高作物产量与水氮利用效率的重要途径。但有关高产水稻作物与土壤的水分与氮素互作效应及其机制尚不清楚。本项目拟从水稻根系形态生理、地上部生长发育与产量形成、土壤理化和生物学特性、氮损失和温室气体排放等方面阐明高产水稻作物与土壤的水氮互作效应及其生物学过程，建立水稻高产与水氮高效利用的水氮耦合模型；从根-冠信号传递、内源激素-氮代谢系统、蛋白质和基因表达等方面揭示水氮耦合调控水稻吸收利用水分和氮素及其高效利用的机制；研究在不同稻作方式、不同灌溉和氮肥管理模式及秸秆还田条件下作物与土壤的水氮互作效应，探明协同提高水稻产量和水氮利用效率的调控途径和关键栽培技术。通过本项研究，可以获得水稻高产与水氮高效利用科学机制的新认识，为构建水稻高产高效的作物-土壤综合管理技术体系提供重要理论支撑。

To fully utilize the synergistic interaction between water and nitrogen on the crop growth and soil quality is an important approach to increase crop yield and water and nitrogen use efficiency. However, the interaction between water and nitrogen on the crop and soil and its mechanism in high-yielding rice are yet to be understood. This proposed project aims to (1) elucidate the synergistic interaction between water and nitrogen on the the crop and soil for high yield, high water use efficiency (WUE) and high nitrogen use efficiency (NUE) and its biological process in rice through investigating physiological and morphological traits of roots, shoot growth and development, yield formation, soil physical, chemical and biological characters, nitrogen loss and the emission of green-house gases from the paddy, and establish a water-nitrogen coupling model for high yield and high WUE and NUE; (2) understand the physiological and molecular mechanism in which high-yielding rice absorbs and utilizes water and nitrogen efficiently through investigating root-shoot hormonal signals, the relationship between hormones and nitrogen metabolism, and protein and gene expressions; and (3) explore crop and soil management approaches and key techniques for increasing grain yield, WUE, and NUE of rice through investigating the water-nitrogen interaction on the crop and soil under different transplanting systems, irrigation patterns, nitrogen management methods, and the straw residue incorporation into soil. The output of the proposed project will be able to obtain new knowledge on understanding the mechanism in which high grain yield, WUE and NUE could be achieved, and to provide an important theoretical support to establish a crop-soil integrative management system for high yield and high use efficiency of resources in rice.