Alternate wetting and drying (AWD) is a water-saving technology that lowland (paddy) rice farmers can apply to reduce their water use in irrigated fields. In AWD, irrigation water is applied to flood the field a certain number of days after the disappearance of ponded water. Hence, the field is alternately flooded and non-flooded. The number of days of non-flooded soil in AWD between irrigations can vary from 1 day to more than 10 days depending on the soil type. AWD has also been used for other crops, such as sugarcane.

Water savings may be up to 15 to 25 percent with no yield penalty. AWD promotes root development, thus reducing plant lodging. In pump irrigation systems, it reduces pumping costs and fuel consumption and an increased income of USD 67 to 97 per hectare (IRRI, 2013). It reduces 30 to 70 percent of methane emissions depending on the combination of water usage and management of rice stubble. It also promotes higher zinc availability in soil and grains by enabling periodic aeration of the soil, which releases zinc from insoluble forms and makes it available for plant uptake. AWD is a water saving technology for lowland (paddy) rice production under irrigation. A special form of AWD is the System of Rice Intensification (SRI), whereby rice is broadcast – so that a large root system develops, and the rice is not all the time inundated. The challenge with the AWD and SRI methods is that more weeds develop because the land is not all the time covered with water.

References: IRRI, 2013. Rice farming: saving water through Alternate Wetting Drying (AWD) method, Indonesia (http://www.fao.org/3/ca4023en/ca4023en.pdf)
Additional sources: Video: Alternate wetting and drying (AWD)–using less water to grow rice (https://www.youtube.com/watch?v=tfKWKfagfFs)