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Topping/pinching in cotton

Topping — also called de-topping, nipping or pinching — is the mechanical removal of the apical bud of the cotton plant to release apical dominance, halt vertical growth and redirect assimilates into sympodial (fruit-bearing) branches and bolls. The operation is a key complement to the high-density planting system.

Principle

Apical dominance in cotton suppresses lateral branching; removing the terminal bud diverts hormonal signals and photosynthate to existing and new sympodial branches. Combined with chemical canopy regulators such as chlormequat chloride (a gibberellin-biosynthesis inhibitor), topping produces a compact, determinate-like canopy with concentrated boll formation.

Implementation

The terminal portion of the main stem is removed by hand or with a topping implement when the plant reaches approximately 90-100 cm height. In Indian HDPS trials, topping combined with a chlormequat-chloride spray has produced 20-21 sympodial branches and approximately 36 bolls per plant, with seed cotton yields of roughly 1,635 kg/ha. The operation is best timed before excessive vertical growth has occurred but after a sufficient number of sympodial branches have set on the lower main stem.

Adoption context

Topping is integral to the CICR-recommended HDPS package (High Density Planting System Cotton) and is increasingly used with compact varieties on closer row spacing (see Cotton Spacing Row Options). It shortens crop duration, improves canopy light penetration and air movement, reduces sympodial overlap, and produces a plant architecture suitable for two-pick or mechanical harvest — a relevant consideration where picking labour is scarce (Cotton Picking Labour).

Limitations

Topping is labour-intensive on conventional smallholdings and must be timed carefully. Premature topping reduces boll number; late topping forfeits the canopy-management benefit. In indeterminate hybrids under abundant irrigation, regrowth from axillary buds may partly negate the operation.

See also High Density Planting System Cotton, Cotton Spacing Row Options, Cotton Picking Labour.

References

  1. ICAR-CICR Advisory on Pest and Disease Management 2024. ICAR-Central Institute for Cotton Research.
  2. Response of hybrid cotton to chlormequat chloride and detopping under HDPS. Research article.