Greenhouse gas emission dynamics from rice paddies under different water management and nutrient regimes

Abstract

Reducing methane from rice paddies without simply trading it for nitrous oxide is one of the trickiest challenges in agricultural climate policy. This research measured CH₄ and N₂O fluxes from flooded rice under three water regimes (continuous flooding, alternate wetting-drying, midseason drainage) crossed with three nitrogen rates (0, 120, 180 kg N/ha) over two growing seasons (2022-2023) at Michigan State University’s research farm. AWD reduced seasonal CH₄ by 43% but increased N₂O by 107%. Net Global Warming Potential (GWP) was still 28% lower under AWD than continuous flooding. The combination of AWD with 120 kg N/ha and composted rice straw achieved the lowest net GWP (−37% versus the flooded baseline). These results identify management combinations that cut net emissions without sacrificing yield.