Water management alleviates greenhouse gas emissions by promoting carbon and nitrogen mineralization after Chinese milk vetch incorporation in a paddy soil

Abstract

Water regime and fertilization are key factors regulating rice yield and greenhouse gas (GHG) emissions in paddy soils. However, the knowledge of the interaction effect of irrigation regime and green manure application on GHG emissions is still lacking. This study was carried out across three incorporation rates (0 %, 25 %, 75 % of urea-N) of Chinese milk vetch (Astragalus sinicus L., CMV), a widely used green manure, under three irrigation regimes (alternate wet and dry (AWD), flooding with 2 cm and 5 cm water depth, respectively). Results showed that water management, fertilizer regime and their interaction affected GHG emissions and grain yields significantly. CH₄ emissions increased with water depth and CMV substitution ratio, while N₂O emissions showed the opposite. The lowest global warming potential of CH₄ and N₂O was observed in 25 % CMV under AWD condition. Moreover, the 25 % CMV treatments had higher rice yields and lower GHGI under different water management. In the labile decomposition, the rates of C and N mineralization decreased with increasing water depth. Treatments with 25 % CMV had higher C and N mineralization rates. In summary, 25 % CMV substitution ratio has the highest potential to mitigate GHG emissions under AWD condition.