Impact of alternate wetting and drying irrigation on methane emission from rice paddies

Abstract:

What fraction of a rice field’s methane output can be eliminated simply by letting the soil breathe between irrigations? This research measured CH⁴ and N²O fluxes under alternate wetting and drying (AWD) irrigation versus continuous flooding (CF) in transplanted rice at Anand, Gujarat, during Kharif 2022 and 2023. Closed chambers sampled gas at weekly intervals. AWD reduced seasonal CH⁴ emission by 38.7% (from 4.10 to 2.51 t CO²-eq ha^-1) without a statistically significant yield penalty (5.87 vs. 6.04 t ha^-1). N²O rose slightly under AWD (+14.3%) because aerobic episodes favoured nitrification, but the increase was small in absolute terms (0.18 vs. 0.16 t CO²-eq ha^-1). Net global warming potential fell by 34.2% under AWD. Irrigation water use declined by 24%, raising water productivity from 0.74 to 0.98 kg grain m^-3. These data support AWD as a practical, low-cost strategy for reducing greenhouse gas intensity of rice in western India without compromising yield.