秸秆还田条件下紫云英施氮对土壤有机碳和温室气体排放的影响

In the southern of our country, there are advantages of rich light, temperature, water and higher straw yield, while also facing winter fallow field area, nitrogen fertilizer overdose, Straw returning increased greenhouse gas emission in paddy fields and other practical problems. To explore a new technology, which can not only make full use of the abundant resources, but also can save energy and emission reduction, is the inevitable way out for the development of agriculture in the south. This study carry out research on soil organic carbon accumulation and greenhouse gas emission mechanism of returning straw and increasing typical nitrogen for winter milk vetch in ecological system of paddy field, and explain its effect on the process and mechanism of carbon sequestration function, reveal effects of greenhouse gas about increasing typical nitrogen for winter milk under straw returning, explain the control mechanism of greenhouse gas emission reduction under the condition of straw returning to field. It not only has important scientific significance and practical value for improving soil productivity, enhancing carbon sequestration function and controlling of greenhouse gas emissions, but also can provide important scientific support for energy saving and emission reduction in agricultural production.

我国南方稻区具有光温水资源丰富、秸秆产量高等优势，同时也面临着冬闲田面积大、氮肥施用过量、由于秸秆还田带来的温室气体排放增加等现实问题，探索出一种既能充分开发利用现有丰富资源，又可节能减排的新型技术，是南方农业发展的必然出路。本研究通过开展典型稻田生态系统秸秆还田与冬种紫云英施氮对稻田土壤有机碳累积及温室气体排放机制的研究，并阐明其影响下的稻田增碳过程及其对固碳功能的作用机理，揭示稻田秸秆还田后冬种紫云英施氮对稻田温室气体产生的影响，确定秸秆还田条件下的稻田温室气体减排调控机制，对提高稻田生产力、增强固碳功能，控制温室气体排放具有重要的科学意义和实践价值，为推动农业生产节能减排提供重要的科技支撑

稻田生态系统是人为温室气体排放的主要来源，稻田温室气体排放与农业生产中的水肥管理措施紧密相关。秸秆还田和冬季种植紫云英还田是良好的节肥措施，广泛应用于我国南方双季稻田，然而关于秸秆还田和紫云英及稻田氮肥使用优化管理对土壤温室气体排放的影响及其作用机制还缺乏研究。本项目围绕南方双季稻区秸秆和紫云英优化管理的农学和环境效应，在大田和室内恒温培养试验条件下，利用静态箱地表温室气体排放进行连续监测，对土壤温室气体的减排过程进行了系统研究。研究结果表明：（1）水稻秸秆、紫云英协同还田并减施氮肥的优化管理措施可以提高水稻产量10.57%-14.53%；（2）相比于无秸秆还田的冬闲田，水稻秸秆和紫云英还田并减施氮可以改善土壤理化特征，分别降低了土壤容重，增加了大颗粒团聚体的含量，提高了土壤的碳库管理指数；（3）水稻秸秆和紫云英还田处理相对于无秸秆还田的冬闲田增加了稻田CH4和CO2的周年累积排放量，但是降低了N2O的排放，周年净增温潜势显著增加了16.66%-27.49，温室气体排放强度增幅为4.20%-9.79%；（4）相比于不还田处理，水稻秸秆和紫云英还田各处理显著提高了土壤中甲烷菌功能基因和甲烷氧化菌功能基因的数量，增幅分别为27.27%-53.1%和48.65%-166.67%。本项目揭示了水稻秸秆和紫云英协同还田并减施氮肥的优化管理下的南方典型双季稻田的温室气体产排的时间规律，进一步阐明了紫云英-稻-稻系统下温室气体的排放强度与稻田土壤理化因子及产甲烷功能基因和甲烷氧化功能基因等微生物因子密切相关；并初步建立了低投入高回报管理原则的保障双季稻高产和实现温室气体减排的综合管理措施。