Farm Progress

Leaf grade has created significant economic loss to growers but has also created problems for ginners.In defoliation trials, the hairy variety had higher leaf grades than a smooth variety.More work needs to be done to give cotton farmers more accurate data from which to select and manage varieties. 

Ron Smith 1, Senior Content Director

March 6, 2012

3 Min Read

Leaf grade in Texas cotton has risen over the last decade, and recent research by a Texas A&M graduate student indicates that leaf hairiness may be a contributing factor.

Zach Eder, in a poster presented at the Beltwide Cotton Conferences in Orlando, reported higher leaf grades over the past 10 years resulted in significant dockage to producers.

“Cotton classed through the USDA-AMS classing office in Corpus Christi, Texas, has reported increases in leaf grade values, beginning in 2000,” Eder said. 

The issue has created significant economic loss to growers but has also created problems for ginners who have to take extra steps to clean cotton with higher leaf grades.

He emphasized the importance of reducing leaf grades. The best leaf grade score is zero; the worst is 7. Discounts start at 3, at which point producers may lose 3.45 cents a pound. At a leaf grade rating of 4, discount is 3.6 cents a pound. It increases from there by 0.10 cents for each grade increase until it reaches 7 and a 3.80-cent-per-pound discount.

Eder evaluated harvest aid and variety as possible contributors to increased leaf grade during the 2010 and 2011 growing seasons. In defoliation trials, the hairy variety had higher leaf grades than a smooth variety across multiple levels of defoliation in 2010 and 2011. 

“Currently, several factors are believed to negatively influence the leaf grade values,” he said. “First is the level of defoliation and desiccation prior to harvest. Second is the influence of varietal characteristics, such as leaf hairiness, bract hairiness and leaf and bract size.”

He said chemical defoliation can be unpredictable, depending on several factors, including harvest-aid selection, plant condition, weather prior to and during application, spray coverage, canopy density, translocation, and varietal traits.

“Additionally, hairier varieties are suspected of contributing to higher leaf grades through a ‘Velcro effect.’”

Eder said hairiness ratings in commercial varieties are assigned subjectively from smooth to very hairy, and ratings can be inconsistent.

His research hypothesis included the assumptions that:

  • Higher percentages of defoliation will cause a lower leaf grade in harvested cotton.

  • Reduction of desiccation will yield a lower leaf grade in harvested cotton.

  • Hairy leaf varieties of cotton will amplify leaf and bract trash, resulting in higher leaf grades than smooth-leaf varieties.

Eder anticipated that increased trichome (fine outgrowths or appendages on plants) density and larger bract size would be contributing factors to leaf grades.

In his variety trails, he collected samples of leaf and bract samples, including grab samples at harvest.

He also developed trials for four varieties and five harvest aids with two smooth and two hairy varieties. Another trial included two varieties ( DP0935B2RF and DP0949B2RF) harvested into individual modules.

Research indicated no correlation of harvest aid or level of desiccation and leaf grade rating. But hairiness did.

“Leaf hairiness influences leaf grade more than defoliation when environmental conditions are conducive for higher leaf grades.” Eder said. “Differences between years indicate specific environmental conditions, such as rainfall after harvest-aid application, are needed for high leaf grade.”

He said trichome density varied between varieties and were similar across all trial locations. “Leaf grade increased with leaf and bract trichome density but leaf and bract size did not correlate with leaf grade.”

Eder said more work needs to be done to give cotton farmers more accurate data from which to select and manage varieties.

“We need to evaluate various physiological traits that may influence cotton leaf grades and other fiber quality characteristics,” he said. “And we need to develop an industry-wide standard for leaf hairiness.”

Eder’s research was supported by the Texas State Support Committee, Cotton Incorporated, Cotton Foundation, and Texas A&M University.

About the Author(s)

Ron Smith 1

Senior Content Director, Farm Press/Farm Progress

Ron Smith has spent more than 40 years covering Sunbelt agriculture. Ron began his career in agricultural journalism as an Experiment Station and Extension editor at Clemson University, where he earned a Masters Degree in English in 1975. He served as associate editor for Southeast Farm Press from 1978 through 1989. In 1990, Smith helped launch Southern Turf Management Magazine and served as editor. He also helped launch two other regional Turf and Landscape publications and launched and edited Florida Grove and Vegetable Management for the Farm Press Group. Within two years of launch, the turf magazines were well-respected, award-winning publications. Ron has received numerous awards for writing and photography in both agriculture and landscape journalism. He is past president of The Turf and Ornamental Communicators Association and was chosen as the first media representative to the University of Georgia College of Agriculture Advisory Board. He was named Communicator of the Year for the Metropolitan Atlanta Agricultural Communicators Association. More recently, he was awarded the Norman Borlaug Lifetime Achievement Award by the Texas Plant Protection Association. Smith also worked in public relations, specializing in media relations for agricultural companies. Ron lives with his wife Pat in Johnson City, Tenn. They have two grown children, Stacey and Nick, and three grandsons, Aaron, Hunter and Walker.

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