Integrative Effects Of Tillage And Straw Incorporation On Riceyield And Greenhouse Gas Emission From Paddy Field Under Double Rice Cropping System In Jiangxi Province

Rice is one of the most important cereal crops in China, and more than 60% of the population lives on rice. Meanwhile, paddy fields are an important source of CH4 emissions, accounting for one-quarter of the global anthropogenic emissions. To achieve high yield and low CH4 emission has become an urgent and important scientific problem. Some research indicated that soil tillage and straw incorporation could affect greenhouse gas emission from paddy field, but the interaction effect was not clear. Therefore, we conducted an experiment to investigate the effects of different tillage methods and straw incorporation on rice plant productivity and greenhouse gas emission from paddy field in the double rice cropping region of China. Main results of this paper are as follows:(1) Compared with plowing tillage, both the early and late rice yield were higher with rotary tillage, but the difference was not significant; straw incorporation significantly increased rice yield. The seed setting rate and grain weight were not significantly different among all treatments, and the rice yield is determined by the numbers of effective panicle and grain per spike. The grain number per spike is the most important factor to determine the yield of late rice. Plowing tillage plus all straw incorporation had 7.9%, 23.9% and 10.6% higher grain number per spike than the plowing tillage with stubble incorporation, the rotary tillage plus stubble incorporation and the rotary tillage plus all straw incorporation, respectively. The effective panicle number was the key factor in early rice yield. The effective panicle number was 13.7%, 6.2% and 21.6% higher in rotary tillage plus all straw incorporation than those of rotary tillage plus stubble incorporation, plowing tillage plus all straw incorporation, rotary tillage plus stubble incorporation, respectively.(2) Straw incorporation significantly increased CH4 emissions during both early rice and late rice seasons, but reduced CH4 emissions during the fallow season. Compared with rotary tillage, plowing tillage reduced CH4 emissions without significant affect on N2 O emissions. The CH4 emission showed two peak fluxes in both seasons, and the occurring time was different between the early and later rice. Under both plowing and rotary tillage, straw incorporation significantly increased CH4 emissions than the stubble incorporation. Plowing tillage plus all straw incorporation and the rotary tillage plus all straw incorporation increased CH4 emissions by 26.1% and 7.1% compared to the that of plowing tillage plus stubble incorporation and the rotary tillage plus stubble incorporation in the late rice, respectively. Compared with plowing tillage plus stubble incorporation and the rotary tillage plus stubble incorporation, plowing tillage plus all straw incorporation and the rotary tillage plus all straw incorporation increased CH4 emissions by 5.4% and 6.1% in the early rice, respectively. Also, relative to the stubble incorporation, straw incorporation decreased CH4 emissions by 26.1% and 7.1% in the winter fallow.(3) Over the 100 year scale, global warming potential(GWP) showed the similar trend with the CH4 emission. The GWP of straw incorporation was significantly higher than that of stubble returning, and the GWP of the rotary tillage was significantly higher than that of plowing tillage. GHGI is determined by the rice yield and GWP, thus showed different trend with GWP. The trend of GHGI was similar to that of GWP in the late rice, but not in the early rice. Among the four treatments, plowing tillage plus all straw incorporation was a suggested practice in the double rice fields with high yield and low emission.