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Paddy stage-wise water management

Stage-wise water management in transplanted paddy adjusts ponded depth across the crop cycle to balance yield with water-use efficiency. The classical schedule maintains a shallow film immediately after transplanting, deepens water with crop growth and drains the field before harvest. ICAR-IIRR's Alternate Wetting and Drying (AWD) technology offers a modified regime that cuts irrigation water without sacrificing yield.

Principle

Continuous shallow flooding suppresses weeds and maintains an anaerobic root environment that suits rice, but consumes 1100-1250 mm of water per season. AWD allows the soil to dry between irrigations until the water table drops to 15 cm below the surface, then re-floods the field to about 5 cm. The drying cycle preserves yield because rice roots remain hydrated by the wet sub-surface profile while the saturated phase oxidises and aerates the root zone.

Implementation

After transplanting, water depth is held at about 3 cm and raised to 5-10 cm as the crop grows. Mid-season drainage may be applied at maximum tillering on heavy soils. Final drainage is given 7-10 days before harvest to firm the field for combine operation. Under AWD, a perforated field tube serves as a water gauge to indicate when the next irrigation is due. The technique requires reasonable field levelling so that drying and re-flooding are uniform.

Adoption context

ICAR-IIRR field trials report 15-30% irrigation water saving with no yield penalty under AWD. The drying cycle also drowns brown planthopper eggs and adults at the base of hills, lowering BPH incidence during tiller and panicle stages. AWD is most beneficial in deltaic and command-area paddy where canal supply or borewell pumping costs constrain irrigation.

Limitations

AWD is unsuitable on heavy clay soils that crack on drying or on saline patches where re-flooding mobilises salts; reclamation practices for the latter are covered under Saline Soil Paddy Management. Weed competition can increase during dry phases, requiring more attentive weed control. Field-water depth still needs careful management at panicle initiation and flowering when moisture stress causes spikelet sterility.

See also: Drip Irrigation, Fertigation, Saline Soil Paddy Management, Zinc Deficiency Paddy.

References

  1. Alternate Wetting and Drying. ICAR-Indian Institute of Rice Research.
  2. Water management. IRRI Rice Knowledge Bank.
  3. Improved Water Management Technologies for Rice. ICAR-National Rice Research Institute.