Cooperative Effect of Alternate Wetting and Drying Irrigation and Rice Variety Improvement on Increasing Yield and Water Use Efficiency

Enhancing rice (Oryza sativa L.) productivity and optimizing water use efficiency (WUE) are critical for advancing sustainable agricultural practices. This study selected six mid-season indica rice varieties to investigate the impacts of alternate wetting and drying irrigation (AWD) and conventional irrigation (CI) on grain yield, WUE, grain filling, and root traits. A two-year field experiment demonstrated that AWD significantly enhanced grain yield and WUE. Flag leaf photosynthetic rate and root characteristics, including root weight, root length, root absorbing surface area, root oxidation activity, and zeatin (Z) + zeatin riboside (ZR) contents in panicles, roots, and root bleeding, were superior under AWD across early, mid, and late grain filling stages. The flag leaf photosynthetic rate and root traits, such as root weight, root length, root absorbing surface area, root oxidation activity, and zeatin (Z) + zeatin riboside (ZR) contents in panicles, roots, and root exudates, were found to be superior under AWD during the early, mid, and late grain filling stages. Notably, AWD delayed root senescence during the grain filling stage, which sustained root activity and promoted grain filling, particularly in inferior spikelets. These results indicate that AWD is a promising irrigation regime to improve rice yield and WUE by optimizing grain filling and root traits.