广西是玉米一年两作的主要种植区，单季玉米生长期降雨量约550 mm，基本可以满足生长需要。但由于降雨与作物生长不同步，水分和氮肥缺乏科学管理，导致水肥流失，土壤环境恶化，早玉米常发生阶段性干旱，玉米生产面临着可持续发展的严峻挑战。因此，如何利用较少水氮投入维持作物稳定合理的产量水平，成为当前亟待解决的关键问题。玉米收获后进行全量秸秆还田，对维持甚至提高土壤碳汇有重要作用；水肥协调可改善农田生态环境，是调控玉米生长的关键性因素；水肥条件是影响农田和作物水分、作物光合碳固定以及土壤有机碳变化的重要因子。本项目在课题组原有研究基础上，将水氮-水分生理-光合碳生产-土壤有机碳相结合，在光合产物（秸秆）全量还田的背景下与传统种植模式比较，研究水氮耦合下土壤和植株的水分如何变化，水氮高效利用下的作物水分生理与碳氮素变化，为深入研究环境水碳平衡提供重要理论依据。

Double maize is one of cropping system in Guangxi Zhuang Autonomous Region. The precipitation of single cropping is about 550 mm which meet the needs of crop growth and development. However, maize agricultural production faces many problems, such as asynchronism precipitation and crop growing, mismatch between demand-supply and time-space of water-nitrogen, water and fertilizer loss and soil environment pollution, phased drought of maize, which is a severe challenge of maize sustainable production. So, decreasing water-nitrogen input and increasing of water-nitrogen utilization efficiency under maintain stable yield which is a crucial factor for agricultural scientist. Maize straw total returning is important role for keeping and increasing soil carbon sequestration. Reasonable irrigation and fertilization can improve farmland ecological environment, which is key factor of regulating maize growing. The water and fertilizer conditions impact on farmland and crop water physiology, photosynthetic carbon fixation, soil organic carbon. Under total photosynthetic product (straw) returning and traditional planting pattern, the research combine with water and nitrogen, water physiology, photosynthetic carbon production, soil organic carbon, which results will provide important information for crop water physiology and carbon-nitrogen change, water-carbon equilibrium of environment under water-nitrogen efficient utilization.