Alternate wetting and drying also called intermittent flooding is a technique developed by the International Rice Research Institute (IRRI) to control water consumption in rice fields (CGIAR 2014). This technology saves water throughout the year in areas of variable rainfall. It is designed as a pick-up water system in cases when water consumption is cut. Water levels are monitored and controlled by the removal of excess water, leaving enough water to sustain crops. Alternate wetting and drying reduces greenhouse gas emissions especially methane, which is emitted from flooded rice fields (FAO 2016). The drying phase helps to sustain and develop plant roots. Moreover, costs on fuel used for irrigation are reduced.
To effectively implement Alternate Wetting and Drying practices:
- Step 1: Alternate wetting and drying should be considered by the farmer after two weeks of rice transplant.
- Step 2: The farmer should consider digging half of 30 cm tube into soil to monitor water level.
- Step 3: When the water level is 15 cm below the soil surface the field should be irrigated again with a depth of 3 to 5 cm before water drains.
- Step 4: This cycle should be repeated until flowering stage to avoid disturbing reproduction because at this stage the crops are sensitive to water stress.
- CGIAR, 2014. New irrigation technique can ease drought effects for rice farmers. Montpellier, France.
- Food and Agriculture Organisation (FAO), 2016. Impact of alternate wetting and drying (AWD) on rice pest and the environment. Rome, Italy.
Benefits
- Alternate wetting and drying maintains rice yields in areas with variable rainfall/irrigation water supply.
- Reduces greenhouse gas emission such as methane.
- The technology can be carried out in regions prone to heavy rainfall.
Drawbacks
- Water levels need to be monitored carefully to avoid water stress which might decrease yield.
- Not recommended in areas with potential salinity stress as reduced water inputs might aggravate salinity levels and cause yield decline.
