不同麦秸还田方式对周年稻麦轮作农田碳足迹的影响

为明确麦秸不同还田方式对稻麦轮作农田碳足迹的影响，该研究通过开展两年的大田试验，设计了3种麦秸还田方式（麦秸旋耕还田、麦秸翻耕还田和麦秸沟埋还田），并以麦秸不还田为对照，采用静态箱-气相色谱法连续两年对农田温室气体排放进行监测，并对不同麦秸还田方式的生产资料投入和生产过程碳排放及温室气体排放进行全面分析。结果表明：(1）与不还田相比，麦秸还田显著增加了稻季日均CH4排放，稻麦周年全球增温潜势95%来自稻田CH4排放；（2）在水稻季，农田CH4排放占碳足迹总量比例最大，3种麦秸还田方式中，麦秸沟埋还田处理下碳足迹最小，且能比麦秸旋耕还田处理减少4.9%；(3）在小麦季，化肥投入造成的碳足迹所占比例最大，为64.5%~77.4%，其次是土壤N2O的排放；（4）从整个稻麦周年轮作系统来看，与麦秸旋耕还田和麦秸翻耕还田处理相比，麦秸沟埋还田处理能分别减少4.6%和3.6%的周年碳足迹及8.7%和4.9%的周年单位产量的碳足迹。因此，对于稻麦轮作地区，采用麦秸沟埋还田能在一定程度上降低农业生产过程中的碳足迹。

Effects of Different Straw Returning Modes on Carbon Footprint in a Rice-Wheat Rotation System

In order to explore the influence of different straw returning modes on carbon footprint in a rice-wheat rotation system, a 2-year field experiment was carried out. In this study, three wheat straw returning modes were set up (wheat straw retuning with rotary tillage, wheat straw retuning with plowing, and wheat straw ditch-buried returning) with no straw returning as the control. The static chamber-gas chromatography method was used to measure greenhouse gases emission and other carbon emissions were calculated by analyzing emissions from the production of main goods and the associated processes during the life-cycle period of rice-wheat rotation. The results indicated that compared with no straw returning, the wheat straw returning significantly increased the average daily CH4 emission and the annual CH4 emission in the rice field accounted for 95% of the global warming potential. In the rice season, the CH4 emission explained the most share of carbon footprint and the wheat straw ditch-buried returning showed the lowest amount among those three wheat straw returning treatments, which was 4.9% lower than that under wheat straw retuning with rotary tillage. In wheat season, carbon footprint derived from chemical fertilizer input was the largest, accounting for 64.5%~77.4%, followed by N2O emission. For the whole rice-wheat rotation, both carbon footprint and yield-scaled carbon footprint under wheat straw ditch-buried returning were the lowest among the straw returning treatments, which was 4.6% and 3.6% lower than wheat straw retuning with rotary tillage, and 8.7% and 4.9% lower than that with plowing. Thus, wheat straw ditch-buried returning might be an effective way to reduce agricultural carbon emission in rice-wheat rotation system.