Process-based modeling for optimizing delayed flooding to mitigate greenhouse gas emissions in green manure–rice rotation

Incorporating green manure into paddy fields enhances soil organic matter, substitutes N and thus increase its productivity. However, it increases CH 4 emissions under flooded conditions. Therefore, effective water management is essential for controlling emissions. To address this, two-year field experiment and along with a process-based model (WHCNS_Rice) evaluated the impact of flooding period following green manure incorporation. Single and double rice cropping regions in southern China. CH 4 emissions accounted for 82.3%–97.8% of the global warming potential, whereas N 2 O emissions contributed only 2.2%–17.7%. Delaying flooding to 5–15 d, compared to immediate flooding, reduced GWP by 34.9%–78.2%. The WHCNS_Rice model reasonably reproduced greenhouse gas emissions with mean values of the index of agreement, Nash–Sutcliffe efficiency, Pearson correlation coefficient at 0.873, 0.466, and 0.807, respectively, and mean root mean square error values of 0.559 for CH 4 and 0.012 for N 2 O. Simulations under 50-year climate scenarios identified flooding after 5 and 8 d for the single and double rice site’s achieved GWP reductions of 70.7% and 41.5%, respectively. Thus delaying flooding after green manure incorporation is an effective early-stage water management practice for mitigating CH 4 emissions.