Straw return performs better in wheat season than in rice season - From the perspectives of yield and greenhouse gas emissions

Straw return is widely applied for improving soil fertility and crop yields. However, the effects of straw return on soil methane (CH 4 ) and nitrous oxide (N 2 O) emissions differ across cropping systems. Here, we investigate the effects of straw return on both crop yields and greenhouse gas (GHG) emissions in wheat-rice cropping systems through meta-analysis. Across the entire dataset, straw return increased crop yields by 5.4% (P < 0.01) on average (9.0% for wheat yield and 4.1% for rice yield, P < 0.01). Straw return had a positive influence on CH 4 emissions (140.4%, P < 0.01), increasing CH 4 emissions by 87.2% and 160.4% in wheat and rice seasons, respectively. Although the overall effect of straw return on N 2 O emissions across the entire dataset was not significant (+3.6%, P = 0.57), a subgroup analysis revealed contrasting results. Specifically, in-season straw return tended to reduce N 2 O emissions, whereas the absence of straw return during the crop season increased N 2 O emissions. Moreover, we found that straw type and K addition levels were two important factors contributing to heterogeneity between studies in CH 4 emissions and crop yields, respectively. Our findings suggest that straw return has greater benefits for wheat than for rice in wheat-rice cropping systems when both yield and GHG emissions are considered.