Species-specific effects of post-wheat green manure incorporation on spring wheat yield and soil greenhouse gas emissions in an arid irrigated system

Post-wheat green manure incorporation can improve fallow-season resource use and crop productivity, but species-specific effects on soil greenhouse gas emissions and subsequent wheat yield remain unclear in spring wheat systems. A field experiment was conducted from 2022 to 2023 in the Yellow River Basin of Inner Mongolia, China, with five green manure species, namely common vetch, hairy vetch, sesbania, forage rapeseed, and forage oat, and a fallow control. Soil CO2, CH4, and N2O emissions, global warming potential (GWP), greenhouse gas intensity (GHGI), wheat growth, and grain yield were evaluated. The system acted as a source of CO2 and N2O and a sink for CH4. Compared with fallow, green manure incorporation numerically increased cumulative CO2 emissions by 7.29%-44.30% and GWP by 7.44%-39.64%, although treatment differences in GWP were not significant, with CO2 contributing more than 85% of total GWP. It also increased grain yield by 2.96%-11.95%. Despite the numerical increase in GWP, GHGI differed among species. Hairy vetch achieved the highest yield and lowest GHGI, common vetch reduced GHGI relative to fallow, and forage oat showed high yield with the lowest cumulative N2O emission. These results suggest that hairy vetch, common vetch, and forage oat are suitable for post-wheat incorporation in this region.