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Alternate wetting and drying (AWD) in rice Photo: Prathvi Acharya · CC BY 4.0 · source ↗

Alternate wetting and drying (AWD) in rice

Alternate wetting and drying (AWD), also called controlled intermittent irrigation, is a water-management practice in transplanted rice in which the field is allowed to dry to a defined sub-surface water level before re-irrigation, instead of being kept continuously flooded. AWD was developed by IRRI and is promoted in India by ICAR-IIRR Hyderabad, ICAR-NRRI Cuttack and several state extension departments as a tool to save 15-30% of irrigation water and to reduce methane emissions from paddy by 30-50%.

Principle

Continuous flooding wastes water through deep percolation and seepage and creates the anaerobic condition that drives methanogenesis. By letting the field drain to a perched water table 15-25 cm below the soil surface, AWD allows oxygen entry, suppresses methane production and concentrates irrigation events without yield loss because the rice root zone still sits above the water table.

Implementation

A perforated PVC or bamboo "field water tube" (about 30 cm long, 4-7 cm diameter) is installed in the bund corner, with the lower 15 cm buried and slots covering the buried portion. Farmers irrigate to 5 cm ponding, then watch the water level in the tube. When it falls 15 cm below the soil surface ("safe AWD"), the field is re-flooded. The cycle is suspended during panicle initiation through flowering, when continuous shallow flooding is restored to avoid pollen sterility. Field levelling and good bunds are prerequisites.

When and where it applies

AWD is recommended for transplanted irrigated rice on medium and heavy soils with controllable water inlets - canal commands, lift-irrigated and bore-well irrigated paddy. It is compatible with Rice Dsr Direct Seeded Rice Punjab, Direct Seeded Rice Broadcast and Rice Sri System Rice Intensification water-saving methods. ICAR-IIRR has demonstrated AWD across Telangana, Tamil Nadu and Karnataka with adoption rates rising in groundwater-stressed blocks.

Limitations

AWD requires reliable on-demand irrigation; rain-fed and unbunded fields cannot follow the cycle. Sandy or porous soils drop water levels too fast and either fail safe-AWD criteria or save little water. Iron and zinc deficiency may surface on prolonged aerobic phases (Micronutrient Deficiency Paddy). Weed pressure rises moderately because intermittent drying favours upland weeds, calling for stricter early-season weed management.

See also Rice Dsr Direct Seeded Rice Punjab, Rice Sri System Rice Intensification, Dry Direct Seeded Rice, Direct Seeded Rice Broadcast, Paddy Water Management.

Sources

  1. Alternate Wetting and Drying. IRRI Rice Knowledge Bank.
  2. Water-Saving Technologies in Rice. ICAR-Indian Institute of Rice Research, Hyderabad.