Skip to content

Weed management in transplanted paddy

Weed competition is one of the principal early-season yield constraints in transplanted paddy, particularly where puddling has not produced a clean weed-free seedbed. In direct-seeded systems weeds are an even larger problem and dominate post-establishment operations.

Principle

Post-emergence weed control in transplanted paddy in India is dominated by ALS-inhibitor (acetolactate synthase) herbicides, which provide broad-spectrum control of grasses, sedges and broadleaf weeds when applied at the 2-4 leaf stage of the target weeds on a drained field. The herbicides act systemically through the plant after foliar or soil-water uptake.

Implementation

Common actives and combinations recommended by ICAR-NRRI and state universities include:

  • Bispyribac-sodium 10 SC - broad-spectrum post-emergence
  • Penoxsulam 24 SC - early post-emergence, especially against Echinochloa spp.
  • Pyrazosulfuron-ethyl - sedges and broadleaves
  • Ethoxysulfuron - broadleaves and sedges
  • Combination formulations: penoxsulam + cyhalofop; triafamone + ethoxysulfuron; bispyribac + penoxsulam

Treatment timing is the 2-4 leaf weed stage on a drained field; flooding is restored within 2-3 days to suppress new weed flushes. Pre-emergence treatments (pretilachlor, pendimethalin, oxadiargyl) are layered into direct-seeded systems (Direct Seeded Rice Broadcast, Dry Direct Seeded Rice).

Adoption context

Wet-DSR and Dry-DSR have higher weed pressure than transplanted rice and require layered pre- and post-emergence programmes. PJTSAU and ICAR-NRRI bulletins document calibrated herbicide schedules for each establishment method, including the 'Dry-Converted-Wet' DSR system.

Limitations

Widespread reliance on ALS-inhibitor herbicides has selected for resistance in some weed populations, especially in weedy rice and Echinochloa spp. Resistance management - rotating modes of action, using pre-emergence layers, and mechanical and cultural controls (puddling, stale-seedbed) - is increasingly necessary.

See also: Transplanting Paddy, Direct Seeded Rice Broadcast, Dry Direct Seeded Rice, Paddy Nursery Management, Algae Management Paddy.

References

  1. Weed Management Technology for Rice. ICAR-NRRI Bulletin No. 165.
  2. Herbicides. IRRI Rice Knowledge Bank.