Abstract

Cotton production is labour intensive in almost all the developing countries where it is picked by hand. However, due to acute labour shortage in recent times, mechanized harvesting is gaining momentum. It requires the application of defoliants, which reduces the cost of labour and maximum cotton can be picked in a single pick (one picking) and consequently provide timely sowing of next crop. The farmers can get benefit of two crops instead of one single long duration cotton crop. Therefore, a two year study conducted at Agricultural College Farm, Bapatla, Andhra Pradesh, during the kharif of 2018–19 and 2019–20 to know the the effect of different defoliants and their time of application on per cent defoliation and seed cotton yield in High Density Planting American Cotton (HDPS).Three defoliants Dropp ultra, mepiquat chloride and etherel and three times of application 80% of boll opening, Node Above Cracked Boll and Node Above White Flower were included in this research in split plot design with four replications. Per cent defoliation was significantly influenced by different defoliant treatments, as well as time of application. At 21 days after defoliant spray, there was significant increase in per cent defoliation with Dropp Ultra 540 SC (Thidiazuron 360 + Diuron 180) @ 250 mL/ha (91.5%) over other defoliants and at 80% Boll Opening (88.3%), which was on par with NACB (86.9%). Higher seed cotton yield was obtained with application of Dropp Ultra @ 250 mL/ha and found on par with Etherel @ 3000 ppm (D3) and regarding times of application, defoliants applied at 80% Boll Opening recorded maximum yield, which was found at par with NACB method.