Water for agriculture is getting increasingly scarce worldwide. By 2025, 15 to 20 million hectares of irrigated rice fields may suffer from water scarcity. To address problems of water scarcity, researchers have been looking for ways to decrease water consumption of the rice crop. These interventions are called “water-savings” and imply a reduced use of irrigation water.
IRRI, in cooperation with national research institutes, developed the Alternate Wetting and Drying (AWD) a water-saving technology. The technology is based on the knowledge that rice tolerates up to 30% reduced water supply during the main growing period compared to conventional irrigation.
To determine the timing of irrigation, the water level in the soil is monitored by a perforated plastic tube, which is inserted into the rice field. AWD requires irrigation when the water level drops to 15 cm below the soil surface. Lowland (paddy) rice farmers can apply AWD to reduce their water use in irrigated fields. In AWD, irrigation water is applied to flood that field a certain number of days after ponded water has disappeared. 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.
AWD can be started a few days after transplanting (or with a 10 cm-tall crop in direct seeding). When many weeds are present, AWD can be postponed for 2-3 weeks until weeds have been suppressed by the ponded water. Local fertilizer recommendations as for flooded rice can be used.
Ample adoption of AWD improved use of irrigation water, so that the cropping intensity could be increased from ca. 119% to ca. 160% (related to the maximum of 200% in these double cropping systems). According to the revised Intergovernmental Panel on Climate Change, ‘multiple aeration’, to which the AWD corresponds, potentially reduces methane emissions by 48% compared to continuous flooding of rice fields. AWD therefore generates multiple benefits related to methane emission reduction (mitigation), reducing water use (adaption where water is scarce), increasing productivity and contributing to food security.
In 2007, the Bohol Island in the Visayas region – one of the largest rice-growing areas in the Visayas region in the Philippines, experienced a decline in rice productivity and income from existing irrigation systems. The National Irrigation Administration (NIA) created an action plan for the Bohol Integrated Irrigated System (BIIS) which included the implementation of the AWD. The visible success of AWD in pilot farms, as well as in specific training programs for farmers, helped dispell the widespread misperception of possible yield losses from non-flooded rice fields.
When the AWD technology was first introduced in Bangladesh in 2004, the public and private sector, and non-government organizations introduced AWD into their programs, entering validation and pilots to disseminate the technology. IRRI collaborated with the Advisory Service on Agricultural Research for Development (BEAF) of the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH to conduct a study to draw general lessons learned with the AWD technology, and to analyze factors of adoption and short-term impacts.
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A glimpse on how to apply Alternate Wetting and Drying (AWD) in irrigated rice fields.
- Climate-Smart Agriculture
- Reducing methane emissions from irrigated rice
- Water Saving in Rice Production – Dissemination, Adoption and Short Term Impacts of Alternate