Effects of Defoliant Spraying Time on Cotton Yield, Quality and Chemical Composition of Seed

【Objective】 To study the effects of defoliant spraying time on cotton yield, quality and seed chemical composition. 【Method】 A single factor randomized block plot experiment was conducted at the Experimental Station of Manas Academy of Agricultural Sciences in Changji Prefecture of Xinjiang to study the effects of defoliant spraying time on cotton yield, fiber quality, defoliation effect and seed maturity. 【Result】 From the comprehensive effect of spraying defoliant at different times, it could be concluded that the defoliant effect was the best when the flocculent rate was 50%, and the defoliation rate reached 92% 20 days after spraying defoliant. The defoliant was sprayed too early, the plant was not aged, the abscission layer at petiole was not easy to form, the defoliant was sprayed too late, and the low temperature at the later stage could not give full play to the effect of the defoliant. 【Conclusion】 The later defoliant spraying, the higher lint percentage and single boll weight of cotton, but too late spraying would lead to cotton bolls unable to open bolls during harvest, and the effect of defoliation was poor, resulting in excessive impurity content during harvest; the content of protein in the seed was too high, the content of fat was insufficient, and the seed not full, thus affecting the vitality of the seed.The effect of defoliant was the best when the boll opening rate reached 50%.