Cotton Leaf Grade As Influenced by Cotton Defoliation and Varieties

Defoliation of cotton, Gossypium hisrutum L., has been referred to as more art than a science by industry leaders.  The remnants of leaf material in harvested cotton can significantly increase leaf grade values and result in dockage to the producer.  Cotton classed through the USDA-AMS Classing office in Corpus Christi, Texas has reported increases in leaf grade values beginning in 2000.  The impacts of the agronomic variables were studied during the 2010, 2011 and 2012 growing season and data collected were used to identify possible contributors to leaf grade, including leaf pubescence and harvest-aid treatments.  Harvest-aid and harvest-aid by variety trials were initiated in two locations. Variety by harvest-aid trials provided an approach to distinguish the individual impact of the leaf hairiness and defoliation.  Wide ranges of defoliation and desiccation levels were obtained with the five treatments and were imposed over a smooth and hairy leaf variety. In defoliation trials, fifteen defoliation treatments were applied and post-application measurements, including percent defoliation and desiccation, were collected. One row from each 40’ plot was harvested with a cotton picker.  Subsamples were collected and lint samples were ginned on a miniature gin in Lubbock, TX and HVI fiber analyses were process in the Fiber and BioPolymer Institute in Lubbock.    Defoliation had no significant impact on leaf grade during 2010 or 2011.  In the variety by defoliation trial, the hairy variety of cotton had higher leaf grades than a smooth variety across multiple levels of defoliation in 2010 and 2011.  Overall leaf grades were lower in 2011 due to more suitable weather conditions between harvest-aid application and harvesting.