Carbon dioxide (CO2) and nitrous oxide (N2O) emissions from decomposing legume green manures largely depend on soil moisture. A potential management to mitigate N2O emissions could be to incorporate legumes during dry periods based on the short‐term rainfall forecast. The present mesocosm study was designed to examine the impact of soil moisture due to different timing of rainfall after incorporation of legume cover crops on CO2 and N2O emissions.