Smart Irrigation through Automated Alternate Wetting and Drying for Sustainable Paddy Ecosystems

Rice (Oryza sativa L.) is a major staple food crop worldwide, particularly in Asia, where its cultivation plays an important role in food security and agricultural livelihoods. However, conventional continuous flooding requires considerable irrigation water and promotes methane emissions from paddy soils. Alternate Wetting and Drying (AWD) is a water-saving irrigation technique that reduces unnecessary water application by allowing the field to dry periodically before re-irrigation. Although AWD can improve water-use efficiency and reduce greenhouse gas emissions, its manual implementation requires regular field monitoring and timely irrigation. Automated Alternate Wetting and Drying (AAWD) offers a promising solution by integrating sensors, microcontrollers, Internet of Things (IoT) technology and automated pumping systems to regulate irrigation according to predetermined water-level thresholds. This review examines the principles of paddy water management, irrigation requirements, AWD practices, sensor-based monitoring technologies and automation strategies for sustainable rice cultivation. It also discusses the effects of AWD and AAWD on irrigation water use, crop productivity, water-use efficiency and greenhouse gas emissions, particularly methane (CH₄) and nitrous oxide (N₂O). Previous studies have demonstrated that AWD can substantially reduce irrigation water consumption and methane emissions while generally maintaining rice yield under appropriate management conditions. However, excessive soil drying, variations in soil properties, increased nitrous oxide emissions, equipment costs and unreliable water supplies may limit its effectiveness. Sensor-based automation can improve irrigation precision, reduce labour requirements and support consistent implementation of AWD. The review highlights the potential of AAWD to promote efficient water management, maintain crop productivity and reduce the environmental impacts of paddy cultivation. Further research is required to improve system affordability, field-level reliability and adaptability under different agroclimatic conditions.