Fruiting pattern determines cotton defoliation timing

Cotton grown under traditional conventions, and allowed to set bolls naturally, typically sets bolls in an extended growth pattern. Conversely, cotton that is short on water and sprayed with plant growth regulators tends to set bolls in a more compact pattern.

In both extremes the plant may have the same number of bolls, but the more extended fruiting, will have bolls which are spread out over more node zones, compared to a compact crop.

In tests by North Carolina State University researchers, in 2004 there was no yield loss from defoliating the more compact crop earlier than fields with more extended fruiting plants.

The North Carolina researchers defoliated cotton at 40, 60 and 80 days, using a modified early bloom strategy to get a more compact crop and left check plots to achieve more extended fruiting habit.

In the more extended fruiting habit, the cotton crop was set over 40 days, compared to 18-20 days for more compact cotton.

In 2005, researchers recorded no yield response to growth regulators. Still, there was no yield penalty from defoliating compact crops earlier.

The 2006 crop followed the same trends, indicating growers would benefit from defoliating more compactly fruited cotton at 40-60 percent open bolls and would benefit from waiting until 80 percent of bolls are open to defoliate cotton with a more extended fruiting habit.

Regardless of the row spacing or fruiting pattern, Mother Nature and today’s economy require 10 mature bolls per foot of row to produce a bale of cotton under good growing conditions.

More bolls will be needed if they are higher on the plant and less if they are lower on the plant.

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