Yield-scaled global warming potentials from commercial rice systems under alternate wetting and drying irrigation

Alternate wetting and drying irrigation practice (AWD) have been shown to reduce global warming potentials and water use. While many studies on AWD in rice have indicated significant reduction of methane emissions, these experiments were conducted in small plots and often in a research station. Multiple benefits of AWD practice need to focus on commercial rice farm to adequately assess impacts on economic yields. In four-year farm study, AWD irrigation was compared to conventional flooded (CF) system to quantify effects on yields, global warming potential (GWP) and yield-scaled GWP (GWP_Y). Grain yields (9-13 Mg ha^-1) were similar in AWD and CF irrigation. The AWD practice reduced CH₄ emissions by 66% and grain yields were similar to both irrigation systems. AWD reduced GWP and GWP_Y by the same relative amount as CH₄. The GWP practice showed only <1% contribution of N₂O emissions to total seasonal GWP. Proper timing of AWD and longer duration of dry periods showed greatest CH₄ emission reduction while sustaining grain yield. Our results indicate that agronomic benefits of AWD irrigation can be achieved in commercial farm with proper implementation of AWD practice. However, adoption of AWD practice by commercial rice growers requires further study to other rice systems with varying field conditions as there may be negative effects on grain yield and greenhouse gas emissions.