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There are several characteristics that help determine fiber quality. Variety selection is the most critical component for the production of high quality cotton. Management practices throughout the growing season can help maintain fiber quality.
Fiber quality ratings are based on internal testing during product development and include high volume instrument (HVI) testing to determine average fiber quality values for each cotton product. Micronaire is measured by the resistance of airflow through a 2.34 gram fiber sample that is compressed to a specific volume. Cotton fiber length is the average length of the longest 50% of fibers. Strength is measured by breaking the fibers held between clamp jaws. Strength is measured as grams per tex, which is the force required to break a bundle of fibers one tex unit in size. A tex unit is equal to the weight in grams of 1000 meters of fiber.1
Lint (%). This is the average percentage of lint taken from the total weight of seed cotton.
Staple (32nds).This is the average length of the cotton fibers, and is measured in 32nds of an inch. To help maximize fiber length, proper management and ideal growing conditions are necessary during fiber elongation.
Micronaire. This is an indication of average cotton fineness and maturity. Environmental conditions can be a strong factor in determining micronaire.
Strength (g/tex). This value is an indication of the average strength of the cotton fibers: 31 or higher (very strong), 29-30 (strong), 26-28 (average), 24-25 (intermediate), 23 and below (weak).
Length uniformity (%). This measures the evenness and strength of the cotton fibers as a percentage. It is the ratio between the average length and the average length of the longest 50% of the fibers. In general, values above 85 (very high), 83-85 (high), 80-82 (intermediate), 77-79 (low), and below 77 (very low).
Once cotton is harvested, it is stored in either round bale modules or the traditional modules made in rectangular module builders placed on the edge of fields until transported to a ginning facility. To maintain fiber quality during storage, cotton must be properly defoliated prior to harvest. Vegetative material or green trash left in the cotton module can result in excess moisture content, high trash count, and stained cotton lint.
The timing of harvest aid applications and harvest can affect cotton quality. Delaying harvest aid applications can increase the potential for poor late season weather, which may affect cotton quality.
To help protect cotton during storage, rectangular modules should be covered with a high-quality tarp. Tarps should be checked for any tears or pin holes before use. Round modules are wrapped with plastic that covers the circumference of the bale and a few inches on the ends. Any excess moisture in the cotton can cause condensation, so modules should be monitored. When elevated moisture levels occur, temperatures increase within the module compromising lint grade and seed viability. Extreme cases can result in spontaneous combustion. Cotton module or bale temperature should be monitored for the first 5 to 7 days. Ideally, cotton harvested at correct moisture levels should only increase 10° to 15° F in the first 5 to 7 days of module storage, then level off or decrease in temperature. A 15° to 20° F temperature increase during the first 5 to 7 days indicates a high moisture problem and the module should be ginned as soon as possible.2 After the initial daily temperature check, modules should continue to be checked every 3 to 4 days. If a module reaches a temperature of 120° F at any time during storage, the cotton should be ginned immediately.
1 Classification of Upland cotton. Cotton Incorporated. http://www.cottoninc.com/.
2 Hake, S.J., Kerby, T.A., and Hake, K.D. 1996. Cotton production manual. University of California Division of Agriculture and Natural Resources. Pub. 3352.
Web sources verified 10/08/18. 181009134811