Combined application of green manure and straw mulch improves rice yield and mitigates methane emissions

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Rice paddies, a major agricultural source of greenhouse gas (GHG) emissions, require sustainable management to balance increasing grain demand with emissions reduction. Based on a 38-year experiment, this study investigates the combined effects of winter-planted green manure (Chinese milk vetch: Astragalus sinicus L.) and straw mulching on soil properties, rice yield, and GHG emissions in a double rice cropping system. The treatments were: 100 % NPK, reduced NPK with milk vetch (NPK+A), reduced NPK with milk vetch and straw (NPK+A+S), and no fertilizer (CK). Compared to CK, the NPK+A+S, NPK+A, and 100 % NPK treatments significantly improved total nitrogen, available potassium, and rice yields ( p < 0.05). However, the annual methane (CH 4 ) emissions were significantly increased by 162.0 % and 112.1 % in the treatments of 100 % NPK and NPK+A, respectively, but not NPK+A+S, relative to CK ( p > 0.05). Notably, the NPK+A+S treatment significantly outperformed the 100 % NPK treatment, achieving a higher annual rice yield (11.61 t ha −1 vs. 10.77 t ha −1 ) and lower annual CH 4 emissions ( p < 0.05). No marked differences were observed in nitrous oxide (N 2 O) emissions among the treatments. Together, our findings suggest that the combined application of winter-grown milk vetch and straw mulch can improve rice yield, and reduce CH 4 emissions. • Green manure and straw mulch effects on rice and GHG emissions were studied. • NPK with/without organic amendment improved soil properties and rice yields. • NPK+A+S achieved the highest rice yield and similar methane emissions to CK. • NPK+A+S outperformed 100 % NPK with higher rice yield and lower CH 4 emissions.