Efficacy of defoliants on yield and fibre quality of american cotton in semi-arid conditions

The study was conducted for exploring the effect of Dropp ultra and Ethrel, their application rates and time of application on two American cotton cultivars. The experiment was carried out at Regional Agricultural Research Station, Nandyal with cultivars NH615 and Sivanandi for two consecutive seasons from 2015–2017 in split plot design with three replications. Application of defoliants like Dropp ultra SC (Thidiazuron 360 + Diuron 180) 200 and 250 ml/ha, Ethrel 1500, 2000 and 3000 ppm were carried at 120 and 140 days after sowing respectively. The results of the study indicated that defoliation with Dropp ultra 250 ml/ha recorded higher percentage of defoliation (92.3) and higher seed cotton yield (2207 kg/ha). Application of defoliants at 140 days after sowing significantly recorded higher yields. There was no difference between the treatments in terms of fibre length and fibre strength. However fibre fineness and uniformity ratio were significantly affected by application of defoliants.