再生稻替代双季稻后对农田土壤有机碳及系统净碳平衡的影响

Reform planting pattern of paddy field not only influences food yield security and high-efficient use of temperature and light resources, but also regulates the process of carbon mitigation and sequestration in rice fields. In recent years, ratoon rice has developed quickly in the middle reaches of the Yangtze River, there are growing interests in shifting double rice cropping pattern to ratoon rice cropping system. However, fewer studies were reported on mechanism research of farmland carbon cycling after double rice cropping system alter ratoon rice cropping pattern. In this project, ratoon rice and double rice systems are to be studied through field experiment, combined with laboratory soil culture mineralization experiment, soil organic carbon physical chemistry fractionation technique, and the closed static chamber gas chromatography technique, etc. The aims are to analyze the differences of soil organic carbon fraction and statility of two cropping patterns in different time scales. The characteristics of soil greenhouse gas emission in different planting systems will be made clear. Condition of the net carbon balance of ratoon rice and double rice cropping systems will be revealed in the study. Combined with the monitoring of farmland environmental factors, the correlation mechanism of greenhouse gas emission in ratoon rice and double rice cropping systems will be analyzed. The results that we obtained can acquire more understanding on carbon balance regulation mechanism in the farmland ecosystem of different cropping patterns, and provide theoretical basis for soil fertility promotion, and cropping system reasonable adjustment of paddy field.

稻田种植模式改革不仅影响粮食产量安全和温光资源高效利用，而且调控着稻田固碳减排的过程。近年来，再生稻在长江中游区不断发展，在双季稻区已出现再生稻种植模式，而关于双季稻改再生稻后对农田碳循环的影响机制研究仍不充分。为此，本项目拟以再生稻和双季稻系统为研究对象，通过大田试验，结合室内土壤培养矿化试验、土壤有机碳物理化学联合分组技术、静态箱-气相色谱法等，分析在不同时间尺度上，两种种植模式的土壤有机碳库组成及其稳定性的差异；探明不同种植系统土壤温室气体排放特征；明确再生稻和双季稻系统净碳平衡状况。结合农田环境因子的监测，分析再生稻和双季稻系统温室气体排放的关联机制，为深入探讨种植模式对农田系统碳平衡的调控机制、土壤肥力培育、及稻田种植模式的合理调整提供理论基础。

由于再生稻系统（RR）的年产量高，而成本和劳动力需求相对较低，所以其已成为我国华中地区双季稻系统（DR）的替代种植模式。然而，DR转RR对农田碳循环的影响机制研究仍不充分。因此本研究通过大田试验，结合室内试验分析等手段，通过在DR中使用两个早稻品种（ZJZ17，LY287）和两个晚稻品种（WY103，TY390）以及在RR中使用两个RR品种（YLY911，LY6326），构成DR1（ZJZ17+WY103）、DR2（LY287+TY390）、RR1（YLY911）和RR2（LY6326）4个种植体系，以此来评估碳足迹（CF）和净生态系统的经济效益（NEEB），及分析4个种植模式的土壤有机碳库组成及其稳定性的差异。结果表明：（1）RR替代DR可将年均CF减少27.37%，这可能归因于RR中的再生季作物的年均CF比DR中的晚稻季的年均CF显著减少了87.27%。（2）直接温室气体排放量是两种种植系统中周年CF的最大来源，分别在DR和RR中占43.28%和35.39%。（3）DR转变为RR时显著增加了30.95%的年均NEEB。这一增长可能归因于RR中的主季作物年均产量比DR中的早稻高20.25%；而RR中再生季的年均农业投入成本和CF成本分别比DR中的晚稻低75.32%和87.27%。（4）水稻品种对不同RR的产量和温室气体排放也表现出一定的影响。与YLY911品种的RR相比，LY6326品种的RR显著提高了年均产量和年均NEEB，而降低了年均CF和年均产量尺度的CF。（5）不同种植模式对土壤可溶性有机碳（DOC）和土壤微生物量碳（MBC）的影响依时间段和土壤深度而异；整体趋势是随着土壤层次的加深，土壤DOC含量增加，而土壤MBC含量递减。（6）不同种植模式对不同稳定态土壤有机碳组分的影响表现出组分及空间的差异性，此碳库稳定机制还有待进一步探讨。（7）在我国华中地区，将DR转变为LY6326品种的RR能够同时降低CF、增加NEEB和保持高产，LY6326 品种的RR是一种非常有前景的稻田种植模式。