Paddy fields can gain high productivity with low net global warming potential by utilizing green manure.

The use of milk vetch as winter green manure is common in paddy fields across southern China. The greenhouse effect of co-utilizing milk vetch and rice straw has not yet been reported. In this study, we investigated net greenhouse gas emissions and related environmental factors over two years based on a long-term experiment. The results showed that the application of milk vetch increased rice yields and soil productivity, especially in combination with rice straw utilization. The application of milk vetch increased annual soil carbon sequestration rate by 492 kg/ha without rice straw returning and by 1115 kg/ha with rice straw returning. Compared to rice straw returning, cumulative CO2 and N2O emissions decreased by 3.5% and 16.9%, CH4 emissions increased by 13.3%, and the net global warming potential and greenhouse gas emission intensity reduced by 2135 kg CO2-eq/ha and 0.16 kg CO2-eq/grain yield in co-utilization of milk vetch and rice straw. Compared to winter fallow, the utilization of milk vetch did not significantly increase CH4 emissions, and reduced greenhouse gas emission intensity by 0.13 kg CO2-eq/grain yield. In conclusion, the application of milk vetch mitigated net greenhouse gas emissions by increasing soil carbon sequestration, making it an effective strategy for reducing the carbon footprint and potentially contributing to broader efforts toward carbon neutrality.