Impact of Chemical Defoliants on Chlorophyll Fluorescence, Biochemical Parameters, Yield and Fiber Quality of High Density Cotton.

Background: The cotton growing farmers in India are facing major problem at the time of harvest due to labor shortages, asynchronized boll opening, leaf trash in the cotton, which is reducing the boll picking efficiency and fiber quality. Presently, the Indian cotton industry is moving towards mechanical harvesting by cotton harvester. Defoliation or leaf abscission is induced in cotton as a natural physiological process which usually is inadequate for a complete mechanical harvest of cotton. Defoliation before harvest is often induced by managing the plants so that senescence, abscission (separation) layer development and leaf drop are encouraged. Chemical defoliants induce leaf abscission, hasten mature boll dehiscence and inhibit regrowth. Selection of appropriate defoliants is one of the critical decisions in cotton production. Their use can result in increased manual as well as machine harvest efficiency, reducing boll rot and the trash in seed cotton. The physiological basis of defoliation in cotton is essential to understand the role of appropriate defoliant with time of application. Hence, the objective of the study was to evaluate the defoliation efficiency, boll opening percentage and to know the physiological basis of defoliation in response to different defoliants and time of application in high density Cotton cultivation which eases the mechanical harvesting. Methods: In this field investigation during 2018 - 2019 at Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore was carried with seven different defoliants and three different time of defoliants application were fixed based on crop maturity and duration of the crop. In this study, high density cotton variety CO 17 was used as experimental material. A series of lab and field analysis were determined on defoliation process, physiological attributes, boll opening percentage and seed yield and quality. The collected data were subjected to statistical analysis. Result: Our investigation exploring the effect of different defoliants on physiological, biochemical, yield and quality parameters of high density Cotton. Among the different defoliants and time of applications, two defoliants and two times of applications works better in terms of better defoliation, boll opening rate, physiology, yield and quality. The physiological and biochemical effects of defoliants on defoliation process were discussed. The present work will be useful for mechanized picking with these effective defoliants without loss of yield and quality loss in cotton. [ABSTRACT FROM AUTHOR]