Intermittent drainage in paddy soil: ecosystem carbon budget and global warming potential

Intermittent drainage of rice fields alters soil redox potential and contributes to the reduction of CH4 emission and thus may reduce net global warming potential (GWP) during rice cultivation. Incorporation of green biomass helps maintaining soil organic matter, but may increase CH4 emission. We investigated net ecosystem carbon budget (NECB) and net GWP under two water management regimes-continuous flooding and intermittent drainage-having four biomass incorporation levels (0, 3, 6 and 12 Mg ha(-1)). Water management and biomass incorporation level demonstrated significant (P < 0.05) interaction effect on the NECB and GWP. Intermittent drainage decreased the NECB by ca. 6-46 % than continuous flooding under same rates of cover crop biomass (CCB) incorporation. Moreover, intermittent drainage reduced seasonal CH4-C fluxes by ca. 54-58 % and net GWP by 35-58 % compared to continuous flooding. There was also no significant reduction in rice yield because of intermittent drainage under similar CCB. This implies that incorporation of 3 Mg ha(-1) CCB and intermittent drainage could be a good option for reducing net GWP and higher grain yield.