Micro-Irrigation in Rice (Oryza sativa L.): A Review of Advances, Challenges and Future Prospects

Rice (Oryza sativa L.) is a major staple crop, but continuous flooding in conventional production systems requires substantial irrigation water and can contribute to greenhouse gas emissions. This narrative review examines the applicability of micro-irrigation technologies in rice cultivation, focusing on surface drip, subsurface drip, sprinkler and micro-sprinkler systems. It also considers rice establishment methods, irrigation scheduling, crop performance, water productivity, nutrient management, environmental effects and economic feasibility. The reviewed literature indicates that controlled irrigation may reduce irrigation water use under suitable conditions, although effects on grain yield and water productivity differ according to soil characteristics, climate, crop establishment and scheduling. Approaches based on irrigation water-to-cumulative pan evaporation ratios, soil moisture thresholds and sensors may support more precise water application. Fertigation and leaf-based nitrogen management tools may further assist nutrient supply when appropriately calibrated. Reduced periods of soil saturation may lower methane emissions, but environmental effects require assessment alongside other greenhouse gases and local management conditions. Adoption is constrained by installation and maintenance costs, potential emitter clogging, energy requirements and limited technical support. Major research needs include longer-term field studies, region-specific irrigation recommendations and economic assessment for smallholder farmers. Nanobubble technology and automated scheduling warrant further field evaluation. Overall, micro-irrigation may improve water productivity in suitable rice systems, but its effectiveness and practicality cannot be generalised across all production environments.