秸秆还田与脲酶/硝化抑制剂耦合施用对稻田CH4和N2O排放的影响及其机理探讨

Wheat straw returning is strongly recommended in rice paddies due to the improvement of soil fertility and the protection of ecological environment. But it may cause the soil lack of nitrogen fertilizer and need extra higher N because the main components of wheat straw are lignin and cellulose and C:N ratio is relatively high. The combined application of urease/nitrification inhibitor and wheat straw application in paddy fields is expected to reduce CH4 and N2O emissions and to alleviate the high nitrogen application that may generate high NO3- and cause ecological environment effect. Taking the typical rice planting area in China as the research object, this project studies the combined effect of the straw returning and urease/nitrification inhibitor application on CH4 and N2O emissions from paddy fields using the "Closed Chamber-Gas Chromatography" method. Fresh soils are sampled through the typical rice growth periods (turning green period, tillering stage, elongation stage and heading stage) for the incubation experiment. In the incubation experiment, we analyze the microbial activity, soil enzyme activity, all kinds of N potassium forms and transformation which are related to CH4 and N2O emissions to study the mechanisms. From the aspects of agricultural cost, crop yield and comprehensive greenhouse effect, we assess the environmental and economic benefits of the combination of wheat straw returning and urease/nitrification inhibitors with the objective to recommend a good rice paddies management that may mitigate the emissions of CH4 and N2O.

稻田秸秆还田因提高土壤肥力和保护生态环境而受到大力推荐，但秸秆的主要成分是木质素和纤维素等，C:N比较高，施入土壤后容易造成土壤供氮不足而需要额外配施高量氮肥。脲酶/硝化抑制剂与秸秆耦合施用有望降低稻田CH4和N2O排放量和缓解高氮施入产生NO3-造成的生态环境效应。本课题选取我国典型水稻种植区为研究对象，采用"密闭箱-气相色谱法"观测秸秆与脲酶/硝化抑制剂耦合施用对稻田CH4和N2O排放的影响。通过典型水稻生长期（返青期、分蘖期、拔节期、抽穗期）采集新鲜土样进行室内培养实验，分析与CH4和N2O产生过程有关的微生物活性、土壤酶活性、各种N素形态与转化，从过程机理上探讨秸秆与脲酶/硝化抑制剂耦合技术对CH4和N2O排放的影响。从农业成本、作物产量和综合温室效应等方面，系统评估稻田秸秆还田和脲酶/硝化抑制剂的环境效益、经济效益和推广价值，旨在提出有利于减缓温室气体排放的稻田管理措施。

稻田秸秆还田因提高土壤肥力和保护生态环境而受到大力推荐，但秸秆的主要成分是木质素和纤维素等，C:N 比较高，施入土壤后容易造成土壤供氮不足而需要额外配施高量氮肥。脲酶/硝化抑制剂与秸秆耦合施用有望降低稻田 CH4 和 N2O 排放量和缓解高氮施入产生 NO3-造成的生态环境效应。本课题选取我国典型水稻种植区为研究对象，采用“密闭箱-气相色谱法”连续三年观测秸秆与脲酶/硝化抑制剂耦合施用对稻田 CH4 和 N2O 排放的影响。结果表明，秸秆还田与脲酶/硝化抑制剂耦合施用是降低稻田N2O排放的重要措施，但一定程度上促进了稻田CH4排放。秸秆与抑制剂耦合施用提高了20%的综合温室效应，同时提高4-6%的水稻产量。水稻生长期水分管理是影响稻田CH4和N2O排放的重要因素，秸秆与抑制剂耦合施用的同时，需要考虑不同水分管理措施对稻田温室气体排放的影响，从而为制定合理的稻田管理措施提供理论依据。