Synergistic mechanism of moderate wetting drying irrigation improving rice productivity and environmental sustainability

Context or problem Rice cultivation encounters substantial challenges in achieving high yield, optimizing water use efficiency (WUE), and minimizing methane (CH4) emissions. Objective Water-saving irrigation regimes are essential in regulating grain yield, WUE, and CH4 emission. This study aimed to investigate if and how the irrigation regimes achieve the above goals. Methods In this study, conventional irrigation (CI) and two water-saving irrigation regimes, intermittent irrigation (II) and alternate wetting and drying irrigation (AWD), were set in paddy fields in 2023 and 2024. Results Compared with CI, II significantly increased grain yield, WUE and economic benefit by 5.61 %, 7.76 %, and 13.14 %, respectively; AWD increased the above indicators by 12.07 %, 12.27 %, and 29.18 %, respectively. This was primarily accomplished by enhancing the production and remobilization of photosynthetic compounds and improving root growth (including deep root distribution, root oxidation activity, and root aerenchyma ratio). The enhanced roots in AWD were closely associated with elevated soil solution oxygen concentration and soil redox potential (Eh), and decreased root ethylene evolution concentration. Compared with CI, II and AWD significantly decreased the CH4 emissions by 19.27 % and 29.65 %, respectively. II and AWD significantly increased the ratio of methanotrophs and methanogens, which is ascribed to the increase in root oxidation activity, soil solution oxygen concentration, and soil Eh. II and AWD decreased the root aerenchyma ratio. These modifications would enhance CH4 oxidation, and limit CH4 production and transport. Conclusions The adoption of the moderate wetting drying irrigation regime may synergistically enhance rice productivity and environmental sustainability by improving photosynthetic output, root vitality, and soil environment. Implication This study provided a practical solution for rice cultivation, aiming to balance yield and environmental stewardship.