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The International Rice Research Institute (IRRI) has developed an irrigation technique called alternate wetting and drying (AWD) that can cut down water use in producing rice by 25 per cent
The technique is currently being introduced to farmers across Asia. IRRI said that it typically takes 2,000 litres of water to produce a kilogramme of paddy (unmilled rice) and AWD can save up to 500 litres of water per kilogramme of rice.
Recently, water supply to about 27,000 rice farmers in Central Luzon in the Philippines was cut off due in part to decreasing water levels at Angat Dam, bringing attention to the need for everyone to save water for growing rice, IRRI said.
Reiner Wassmann, head of IRRI’s climate change research, noted, “El Niño conditions are predicted to progress over the coming months. Although it is difficult to project the exact rainfall amounts, rainy seasons in El Niño years typically have shorter periods of rain and less rainfall amounts.
“Water shortage at the Angat-Maasim River Irrigation System (AMRIS), of which Angat Dam is the main water source, is anticipated, as water available for irrigation has gradually decreased over recent years and the Philippines has been experiencing a really dry season this year.”
Departing from the conventional way of growing rice that uses continuous flooding, AWD makes use of the cycle of draining and reflooding of rice paddies, keeping an optimum water level at any particular time.
IRRI said that the AWD technology is applicable to larger irrigation schemes like the AMRIS, but it is also just as useful for rice farmers who rely on pump irrigation. AWD use means greater farming incentives as lower water consumption translates right away into savings on fuel cost and higher net income for farmers, it added.
In Vietnam, farmers have reportedly credited AWD for yield increases. Decreased water use also reduced the occurrence of ‘lodging’ (when rice plants keel over due to heavy rain) and helped the plant grow better tillers (‘branches’ that eventually carry grain) and stronger roots. The resulting improved field conditions helps reduce labor cost at harvest, as mechanical harvesting becomes feasible.
AWD also helps reduce greenhouse gas (GHG) emissions, specifically methane, by up to 50 per cent. Methane emissions are caused by flooding of rice fields. Research by scientists from IRRI and its partners have helped AWD evolve into one of the most mature GHG mitigation methods in the agriculture sector, the international organisation said. AWD could, thus, become a key component for GHG mitigation in many Asian countries.