Characteristics of CH4 emission and greenhouse effects in double paddy soil with conservation tillage

Chinese. 【目的】传统耕作方式和秸秆焚烧造成土壤有机质的大量损失,使农田成为温室气体一个重要排放源,本文旨在研究保护性耕作对稻田CH4排放通量及其温室效应的影响,为评价耕作措施对土壤固碳潜力和温室气体减排影响提供依据。【方法】通过对翻耕秸秆不还田（CT）、翻耕秸秆还田（CTS）、旋耕秸秆还田（RTS）、免耕秸秆还田（NTS）处理的稻田CH4排放进行连续观测,分析稻田CH4排放特征及其温室效应。【结果】在秸秆还田情况下,早稻生长季旋耕和翻耕的CH4排放量差异不大,但显著高于免耕;晚稻生长季旋耕CH4排放量显著高于翻耕和免耕;冬闲季节各处理CH4排放量较小,翻耕CH4排放量显著高于旋耕和免耕。在翻耕情况下,秸秆还田处理和秸秆不还田处理全年CH4排放特征基本相同。秸秆还田主要增大晚稻生长季和冬闲季节的CH4排放,对早稻生长季CH4排放影响较小。全年CH4排放导致的温室效应为RTS〉CTS〉NTS〉CT,且差异均达显著水平。各处理全年CH4排放主要来自早晚稻生长季,冬闲季节占的比重很小均不到1%。与翻耕相比,旋耕对温室效应的贡献是翻耕的1.98倍,而免耕减小温室效应,约减排15%。与秸秆还田相比,秸秆不还田减小温室效应,约减排42%。【结论】目前双季稻区推行保护性耕作的主要措施旋耕秸秆还田对温室效应的贡献最大,秸秆不还田和免耕均有利于减小温室效应。但考虑到秸秆还田有利于提升地力,且秸秆以其它方式处理导致的温室效应还有待于研究,建议在长江中下游双季稻区推广以免耕秸秆还田为主的保护性耕作。

English. [Objective] The conventional tillage and burning straw caused much losses of soil organic matter, which made cropland be an emission source of greenhouse gas. The research has been conducted to study the effects of conservation tillage on CH4 emission from paddy soil and explore the greenhouse effect. Further theoretical guide for forecasting carbon sequestration potential of soil and reducing emission of greenhouse are to be provided. [Method] The analysis of greenhouse gas emission character and greenhouse effect is based on observing greenhouse gas emission from treatments of CT, CTS, RTS and NTS. [Result] When refer to the different tillages, the difference in CH4 emission flux between CTS and RTS was little during the early rice growth, but they were much more than NTS. During the late rice growth the CH4 emission flux of RTS was much more than CTS and NTS. In winter-fallowed season the CH4 emission flux of each treatment was relative small, and CTS was almost bigger than RTS and NTS. When refer to the straw return, the seasonal emission characters of CH4 from CT and CTS were the same, and in the monitoring period the CH4 emission flux of CTS was a little more than CT. Returning straw mainly increased the CH4 emission of late rice field and winter-fallowed field, and had less influence on early rice field. The greenhouse effect of the whole year was RTS〉CTS〉NTS〉CT, and they were significantly different. The greenhouse effect of paddy soil mainly attributed to CH4 emission from early rice field and late rice field, and little attributed to CH4 emission from winter-fallowed field. Comparing to CTS, RTS increased the CH4 emission, and almost 1.98 times of CTS, and NTS released by 15%. Comparing to CTS, CT released CH4 emission by 42%. [Conclusion] RTS was the main way of tillage in the double cropping paddy soil area, and it also lead to the most CH4 emission. This research also showed results thai no straw returning soil and no tillage were attributed to release CH4 emission. Straw return to soil is good for soil nutrient and the greenhouse effect of straw in other ways needs to be further researched, so it is suggested that the double-cropping paddy soil area should use conservation tillage and return the straw to soil.