New market demand for improved fiber and cotton quality is not only changing cotton variety breeding and cotton production objectives, but it's also focusing more attention on how cotton is harvested and processed, according to Tommy Valco, USDA-ARS, Stoneville, Miss.
A gin or harvesting machine can't improve the quality of cotton, noted Valco, speaking at the 2005 Beltwide Cotton Conferences, in New Orleans. But they can preserve the quality of the cotton that runs through them.
Too much processing at the gin can create neps problems. Ginners should also be aware that short fiber is created from increased machine operation, improper settings on lint cleaners and improper moisture content during processing.
Moisture is the most critical factor influencing fiber and cotton quality in the harvester and the gin, according to Valco. “Make sure you begin harvesting at less than 12 percent moisture. This provides a good safe environment for us to store cotton.”
Growers should make sure all harvesting equipment is properly adjusted. “This prevents trash from coming into the gin. Also make sure spindles and doffers are properly adjusted so we don't have spindle twist or preparation problems at the gin.”
Valco noted that many farmers had an unusual “problem” in 2004 due to high yields — they often couldn't make it to the end of the field before they had to dump their baskets. “It's a good problem to have in one way, but harvesting efficiency dropped, and growers were putting modules where they shouldn't have been.”
Valco's advice is to avoid placing modules in low spots in the field and be sure modules are accessible to module trucks. In addition, inspect or routinely replace worn out tarps used for module covers. Monitor the temperature inside modules for the first five to seven days to make sure it doesn't increase gradually. Modules should be ginned immediately if temperatures rise 15 to 20 degrees.
A critical factor in the ginning process is the condition of incoming cotton, according to Valco. “If we send wet modules or modules that are wet on the bottom, we're not going to get a very good quality of cotton.”
Another rule of thumb is to avoid processing cotton at less that 5 percent moisture. “Our research has shown that 6 to 7 percent is optimum for cleaning and processing. Use the lowest drying temperature as possible. Avoid temperatures over 250 degrees and never use drying temperatures over 350 degrees. Getting fibers too hot will make them brittle and more likely to break during the ginning process.
“If the cotton is too dry, we can improve cleaning and color grades, but we can also damage the cotton. If it's too wet, we may do a poorer job of cleaning, although we can improve the staple length. There is a compromise the ginner has to make.
If a gin adds moisture at the lint slide, “make sure that moisture is not over 7.5 percent. If you are restoring moisture at the lint slide, make sure you have a uniform application in the bales.
“Technology such as gin process control is available to help ginners observe the quality of the fiber as it is being processed. Communication is needed between the grower and the ginner to make sure everyone understands what the target levels are.”
Make air-conveying systems as simple and direct as possible, eliminating unnecessary elbows and valves, Valco says. Excessively high conveying speeds can crack seed and increase preparation and seed coat fragments.
Valco suggests that ginners follow a maintenance program to keep controls in good working condition. A drying system must have the ability to change the temperature rapidly to meet the drying demands, thus saving fuel and avoiding fiber damage.
Gin schools can also help ginners do a better job of processing cotton. Three-day schools administered by USDA are located in Stoneville, Miss., Las Cruces, N.M., and Lubbock, Texas. “We train them on the proper operation of gins, teach them how to use certain moisture instruments and tell them about the importance of fiber quality and how it affects textile operations.”
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