Straw returning is of great significance for improving soil structure, soil fertility, crop yield, and quality. However, straw returning causes environmental problems such as increased methane emission and non-point source pollutant emission risk. How to reduce the negative effects of straw returning is an urgent problem to be solved.In this study, the effects of aerobic treatment on carbon and nitrogen concentration in surface water and greenhouse gas emissions in paddy fields with different treatments of straw returning were systematically compared.The results showed that different treatments of straw returning significantly increased chemical oxygen demand (COD) in the surface water of the paddy field and significantly promoted the methane emission of the rice field and the global warming potential (GWP), although it slightly reduced N2O emission. The increasing trends showed that wheat straw returning>rape straw>broad bean straw returning.Straw returning increased rice yield when compared with the control without straw returning, but the difference was not significant. Aerobic treatment reduced the COD in surface water by 15%-32%, the methane emission of the paddy field by 10.4%-24.8%, and the GWP of paddy field by 9.7%-24.4% under different straw returning treatments, without affecting the rice yield. The mitigation effect of aerobic treatment with wheat straw returning was the best. The results indicated the potential of oxygenation measures in greenhouse gas emission mitigation and COD emission risk reduction in straw returning paddy fields, especially in wheat straw returning paddy fields.
Keywords: field surface water COD; greenhouse gas emissions; oxygenation; rice; straw returning; yield.