Alternate Wetting and Drying (AWD) is a rice management practice developed by IRRI. The practice reduces water use by up to 30% and methane emissions by 48% without impacting yield. With efficient nitrogen use and application of organic inputs to dry soil, the practice can reduce emissions even further, enhance nutrient efficiency, and deter insect infestation. AWD has been field tested and validated by rice farmers in Bangladesh, Indonesia, Lao PDR, Philippines, Myanmar, and Vietnam. AWD is now being mainstreamed in extension efforts by formal extension institutes and NGOs in a number of countries in Southeast Asia.
The term AWD is also known as controlled irrigation (CI) or intermittent irrigation, distinct from farmers’ conventional practice of continuous flooding (CF). The number of days of nonflooded soils can vary from 1 to more than 10. In this technology, the farmers are taught to monitor the depth of the water table in the field using a perforated water tube. The practice, which commences at 1 to 2 weeks after transplanting, involves draining the field until the water level reaches 15 cm below the soil surface (Fig. 1). Immediately, the field is re-flooded to a ponded depth of around 5 cm before re-draining. This irrigation scheme is followed throughout the cropping season except from 1 week before and 1 week after flowering (Fig. 2). The threshold of water at 15 cm below the soil surface is called “safe AWD,” as this will not cause any yield decline because the roots of the rice plant will still be able to capture water from the saturated soil.
AWD technology has been proven to mitigate methane emissions. The greenhouse gas (GHG) methane is produced anaerobically by methanogenic bacteria that thrive well in paddy rice fields. Hence, flooded rice fields are a large source of methane emissions (in fact, the second largest anthropogenic source after ruminant livestock). Because periodic aeration of the soil inhibits methane-producing bacteria, AWD can reduce methane emissions by up to 50%.
Problem addressed: Water Scarcity.
IRRI (International Rice Research Institute)
Los Baños, Philippines
Tel: +63 2 580 5600 or +63 2 845 0563
Fax: +63 2 580 5699 or +63 2 845 0606
Source: CGIAR (Consultative Group on International Agricultural Research) - Research Program on Climate Change Agriculture and Food Security website