News: Alternate Wetting and Drying is discussed due to its role in reducing methane emissions, saving water, and enabling carbon credit generation in rice farming.
About Alternate Wetting and Drying (AWD) Technique for Rice Cultivation
- Alternate Wetting and Drying (AWD) is is a water-management technology for lowland rice cultivation that reduces water consumption and methane emissions by alternating between flooded and non-flooded periods.
- Core mechanism
- Controlled Irrigation Cycle: Unlike traditional continuous flooding (CF), AWD allows the water level to recede naturally to a specific threshold – usually 10–15 cm below the soil surface – before the field is re-flooded to a depth of roughly 5 cm.
- Monitoring: Farmers often use a simple field water tube (perforated PVC or bamboo pipe) to monitor the subsurface water level.
- Timings
- Initial Phase: Fields are kept flooded for the first 15–20 days after transplanting to establish seedlings.
- AWD Phase: The wetting-drying cycle continues until the flowering stage.
- Flowering Stage: Continuous flooding (3–5 cm) is maintained to prevent moisture stress.
- Post-Flowering: Cycles can resume during grain filling and ripening.
- Benefits
- Water Conservation: Reduces water use by 25–40% compared to traditional methods.
- Methane (CH₄) Mitigation: AWD lowers methane emissions by disrupting anaerobic conditions suitable for methane-producing microbes.
- Cost Efficiency: Decreases irrigation frequency, leading to lower labor and energy (pumping) costs.
- Soil and Crop Health: Enhances root development, improves nutrient uptake, and may reduce lodging.
- Reduces toxic metal accumulation in grains: This method can reduce the accumulation of arsenic, lead, and cadmium in rice grains, with variants like e-AWD significantly lowering their levels.
- Reduces pests and diseases: This method can reduce insect pests and diseases, and periodic soil drying may reduce the incidence of fungal diseases.
- Challenges
- Farmers may initially hesitate to adopt AWD due to unfamiliar irrigation practices.
- AWD requires monitoring of water levels and soil moisture, which needs basic field management awareness.
