INFLUENCE OF EARLY DEFOLIATION ON COTTON YIELD, SEED QUALITY, AND FIBER PROPERTIES

Chemical defoliation of cotton (Gossypium hirsutum L.) should be carri ed out when all plant processes are complete. However, initiating defo liation treatment prior to this time of plant development is necessary in most instances. The objective of this research was to determine th e influence of chemical defoliants on yield components, fiber quality and seed quality of an early-maturing cotton cultivar when application s were made at 20, 40, 60, or 80% open bolls. Yield loss occurred when defoliants were applied at 20 and 40% open bolls. However, there was no evidence to indicate that applications made at 60% or greater resul ted in yield loss or lower quality of the fiber. Increases in fiber st rength and length were observed when defoliants were used at 20% open bolls. This was attributed to the physiological abscission of younger bolls, leaving a higher percentage of older, more mature bolls contain ing fiber of greater length and strength. In general, defoliant treatm ents should not be applied prior to 60% open bolls in order to safegua rd against potential losses in yield and undesirable changes in fiber quality. Yield losses and quality reductions occurred due to improper timing, irrespective of defoliant used.