Effects of Water-Fertilizer Synergy Management on Sustainable Rice Production: Growth, Yield, and Environmental Impacts

To address the dual challenges of water scarcity and non-point source pollution in global rice cultivation, this study systematically evaluated the interactive effects of irrigation regimes (continuous flooding, intermittent irrigation, shallow-wet irrigation) and fertilization strategies (conventional fertilization, reduced slow-release fertilizer application). Results showed that the combination of intermittent irrigation with reduced slow-release fertilizer significantly suppressed non-productive tillers (productive tiller rate increased to 74.1%), promoted deep root development (root length density increased by 26.7%), and increased grain dry matter allocation by 6.8%. The yield reached 8.52 t/ha, showing no significant difference from conventional practices, while water use efficiency improved by 32% (1.24 kg/m³) and partial nitrogen productivity increased by 28.3%. Environmentally, this treatment reduced methane emissions by 39.5% (225 kg/ha), lowered peak total nitrogen concentration in surface water by 34.2%, and decreased nitrate leaching risks. The study reveals that optimized water-fertilizer management stabilizes yield and enhances efficiency by controlling tiller redundancy and synchronizing nutrient release with root expansion. We recommend adopting an irrigation regime of "water control during tillering + shallow flooding at booting + alternating wet-dry conditions during grain filling," combined with a 40–50% reduction in slow-release nitrogen base fertilizer, to support green rice production. Future research should focus on long-term impacts of water-fertilizer management on soil microbial communities and carbon sequestration.