EFFECT OF DEFOLIANT APPLICATION AT DIFFERENT STAGES OF BOLL MATURITY AND DOSES OF SULFUR ON YIELD AND QUALITY OF UPLAND COTTON

A study was carried out during 2004 and 2005 for exploring the response of cotton to defoliant (Thidiazuron) application at various stages of boll maturity and various doses of sulfur on seed cotton yield and fiber quality parameters at Cotton Research Station, Dera Ismail Khan, Pakistan. Cultivar CIM-473 was planted in split plot design, keeping no application of defoliant, application at 50 and 60% boll maturity as main plots and sulfur doses of 0, 6, 12 and 24 kg ha-1 were adjusted in sub-plots. Bolls plant-1, boll weight (g), seed cotton yield, fiber fineness and fiber uniformity index were significantly affected by defoliant application at different stages, various doses of sulfur and their interaction. Seed cotton yield was greater in the plots where defoliant was applied at the time of 60% boll maturity and the sulfur was also applied @ 24 kg ha-1 during both the years of study. Harvesting was done in this treatment twenty five days earlier than control. While the lowest seed cotton yield was recorded in the plots where neither defoliant was applied nor was the sulfur applied during both the years of experimentation. Quality traits like fiber strength, lint % and staple length were non-significantly affected by defoliant application, various doses of sulfur and their interaction during both the years of experimentation. However, fiber fineness and uniformity index were significantly affected by defoliant application at various stages. It was concluded that for getting early crop with more seed cotton yield of best fiber quality, the cotton crop should be given defoliant application at 60% boll maturity stage along with sulfur dose of 24 kg ha-1 under agro-climatic conditions of Dera Ismail Khan, Pakistan.