Optimizing the Incorporated Amount of Chinese Milk Vetch (Astragalus sinicus L.) to Improve Rice Productivity without Increasing CH4 and N2O Emissions

Chinese milk vetch (CMV) is a leguminous green manure that commonly cultivated in paddy fields and can partially substitute synthetic nitrogen fertilizer. However, the impacts of incorporating CMV on CH4 N2O emissions are still subject controversy. Therefore, we conducted field experiment over three years to investigate under different substitution ratios: urea only (CF); traditional amount (MV); with incorporation ratios 1/3 (MV1/3), 2/3 (MV2/3), 4/3 (MV4/3) MV for partial substitution. Compared CF, MV2/3, MV, resulted increased yields. MV4/3 reduced but by 28.61% 85.60% (2019), 32.38% 103.19% (2020), 28.86% 102.98% (2021), respectively, resulting an overall increase total global warming potential (except 2021). MV2/3 exhibited low greenhouse gas intensity value ranging from 0.46 0.47. Partial least-squares-path model results showed were influenced ratios, which indirectly regulated gene abundances mcrA nosZ. Overall, impact was determined ratios. involved N fertilizer 15.0 t ha−1 CMV, improved rice productivity without increasing emissions, making it recommended approach study area.