Meta-Analysis of Alternate Wetting and Drying (AWD) Irrigation Effects on Methane and Nitrous Oxide Emissions Across Different Climates and Soil Types

Rice cultivation significantly contributes to global greenhouse gas (GHG) emissions, especially methane (CH4) and nitrous oxide (N2O), while also facing increasing water scarcity challenges. Alternate wetting and drying (AWD) irrigation has emerged as a promising water-saving technology that can potentially reduce GHG emissions. This meta-analysis combines data from 47 field studies across different climate regions and soil types to assess how AWD affects CH4 and N2O emissions compared to continuous flooding. The results show that AWD significantly lowers CH4 emissions by 64.5 ± 12.3% across all climate zones and soil types, while N2O emissions increase by 18.7 ± 8.4%. Overall, the global warming potential (GWP) decreases by 42.1 ± 9.8% with AWD irrigation. Climate zone analysis indicated greater CH4 reduction in tropical regions (68.2%) compared to temperate ones (58.9%). Soil texture also plays a role, with clay soils showing the most notable CH4 reduction (71.3%) but also the highest increase in N2O (23.1%). The success of AWD depends on water management practices, nitrogen fertilizer application, and organic matter addition. These findings show that AWD can be an effective climate mitigation strategy for rice farming, but its implementation should consider local environmental conditions.