Effects of water-saving irrigation on rice yield and population quality in Northeast China

Water scarcity is a major constraint on rice production in the black soil region of Northeast China, underscoring the urgent need for water-saving irrigation technologies to support sustainable cultivation. A field experiment was conducted during 2023-2024 at Jiansanjiang Qixing farm, Kiamusze, Heilongjiang province, using the conventional <italic>japonica</italic> cultivar Longjing 31. Three water-saving irrigation regimes—shallow-wet irrigation (SWI), alternate wetting and drying (AWD), and controlled irrigation (CI), were evaluated against continuous flooding (CF) to assess their effects on grain yield and crop population traits. (1) Compared to CF, irrigation water input was reduced by 9.5%-18.9% under SWI, 12.2%-23.4% under AWD, and 17.0%-26.8% under CI. Grain yield increased by 10.5%-11.2%, 7.4%-13.5%, and 2.11%-2.25%, respectively, while irrigation water use efficiency improved by 21.7%-29.9%, 22.3%-39.8%, and 22.0%-29.2%. Yield improvements under SWI and AWD were primarily attributed to increases in total spikelet number, with AWD exhibiting significantly higher water use efficiency than SWI. (2) Both SWI and AWD also enhanced population quality by improving the productive tiller rate, effective leaf area index, spikelets-to-leaf area ratio, non-structural carbohydrate (NSCs) accumulation and remobilization, post-anthesis dry matter production, root activity, and antioxidant defense. Additionally, they maintained higher leaf SPAD values and reduced membrane lipid peroxidation. In conclusion, SWI and AWD not only conserve irrigation water but also optimize physiological performance, thereby contributing to yield enhancement. These findings provide a theoretical foundation for the adoption of water-saving irrigation strategies in rice cultivation within the black soil region of Northeast China.