Abstract:
Defoliation is an important management practice of cotton production. Field
experiments were conducted
for exploring
response of cotton to defoliant application
times at various percentages of boll opening on seed cotton yield and fiber quality.
Experiments were arranged in split
-
plot design with defoliation times (control, 40, 60, and
80% open boll) as the main plots a
nd cultivars (hairy leaf, semi
-
smooth leaf, and smooth
leaf) as subplots, with three replicates. The pooled results indicated that early application
of harvest aid products significantly reduced seed cotton yield, boll number per plant,
micronaire and fibe
r length. Significant reductions in seed cotton yield occurred with
defoliant applications both prior to and after 60% open boll application timing.
Application at 40% followed by boll opening had the maximum number of the green
leaves remaining on the pla
nt at 14, 21, and 28 days after treatments and a corresponding
high trash content and high leaf grade. However, except for the leaf grade, the number of
green leaves remaining on the plant after defoliation and the trash content, varietal
differences were
non
-
significant. Smooth leaf cultivar (SG 125) had the highest number of
green leaves left on the plant after treatment (79.2) compared with hairy (71.9) and semi
-
smooth leaf (77.1) cultivars. It was concluded that
cotton cultivars with varying levels of
l
eaf hairiness impacted the defoliation efficacy of the harvest aid products.
Keywords:
Harvest aids, Leaf hairiness, Micronaire, Open boll percentage, Trash content
