A field of cotton plants loaded with open bolls is every producer's field of dreams. At this point, however, only half the challenge is met. Growers still must defoliate, harvest, put their cotton into modules and deliver the modules to the gin, while keep the cotton clean, dry and free of trash and field debris.
Tommy Valco, USDA/ARS, Stoneville, Miss., researches how to maintain cotton quality and yield from the field to the textile buyer.
“Harvesting cotton when it is too wet or adding too much water through moistener pads can reduce picking efficiency and can cause significant quality loss during storage,” says Valco. “Cotton is rarely dry enough to be harvested at night or early in the morning. Harvesting should be delayed until any dew has dried and relative humidity drops below 60 percent.
“High-capacity pickers or strippers require trained operators and good maintenance programs to insure a timely harvest that produces high fiber quality and yields.”
Herb Willcutt, agricultural engineer with the MSU Extension Service, says good quality begins with variety selection, but environmental and human factors during harvest can compromise lint quality. Those factors include defoliation, harvest, module building and storage and ginning.
“Growers should allow the full effect of defoliation to be achieved before they put pickers in fields. Forcing immature bolls open, then harvesting before they have fully dried, adds unnecessary moisture to stored seed cotton,” he says. “Moisture and immature seed in bolls are a source for microbial activity to begin and spread to other seed cotton in close proximity in a module.
“Good defoliation eliminates many picker problems by keeping headers clean of leaf trash and spindles from gumming, which in turn results in less spindle twist and faster harvesting with less fire danger in headers. It also keeps trash levels to a minimum in stored seed cotton, reducing the tendencies for modules to heat and lint to discolor,” says Willcutt.
The less trash harvested, the less cleaning at the gin and the better the quality of products for customers. Moisture relationships through ginning are also improved since less trash requires less drying for good cleaning. This can translate into improved fiber length in ginning.
Contaminants in fields such as plastic bags, bottles, cans and similar trash could get through the picker, into modules and into gins.
“These materials and garments worn by field and gin workers account for the majority of contamination complaints by mill management,” says Willcutt.
Regular and correct maintenance of pickers helps keep trash out of cotton, helps avoid untimely breakdowns, and prolongs the service lives of pickers, major expenses on a cotton farm.
“Make sure spindles are in good condition — sharp, straight and tight in the bushings — and they all turn when the picker is operating,” says Willcutt. “The relationship of spindles to doffers should be no closer than about 0.003 inch — about the thickness of a dollar bill.
For a picker to be set correctly, bar heights must be set to within a few thousandths of an inch to maintain close doffer-to-spindle clearance on all spindles.
“Closer will cause undue doffer wear and could result in rubber particles in the seed cotton,” says Willcutt.
“Moisture pads should just wipe across spindles as spindles pass beneath. Use a surfactant or spindle oil to aid in removal of green leaf and plant residue from spindles. If spindle wrap occurs, make sure the spindle is clean of plant residue before adjusting doffer clearance,” he adds.
“Increase spindle solution if residue becomes a problem, but be conservative; spindle solution adds moisture to the seed cotton that goes into a module.”
Cleaning picker headers and greasing habits can also reduce trash buildup and fire dangers. Greasing lightly two or more times each day with automatic greasing systems results in less grease in header drum areas, thus less buildup of trash.
“Growers should experiment to find what works best for their management, but a late-evening greasing followed by a pressure washing of the headers in the morning before heading to the field, then a light greasing about noon would be a good option,” says Willcutt.
Picker heads should be operated with a slight tilt to the front, with the front of the header about 1 inch lower than the rear. This lets the front drum pick lower bolls and the rear of the header discharge trash from the bottom of the header.
If heavy trash buildup is a problem, pickers should be cleaned between each dump.
“Newer four- and six-row machines operate without much buildup, and cleaning cabinets every dump in good conditions becomes much less necessary,” says Willcutt. “When trash from headers or baskets is thrown away, make sure it does not get into module builders or where a module may be located later in the season.”
Another factor that can affect the quality of cotton long after it's picked is the location of modules. Accessibility in wet weather will often mean several days' advantage in moving modules to the gin. A module located in a low area may have water pool around the base, soaking and causing several inches of the module to rot. Modules with wet bottoms are more difficult to gin.
“Extra drying may be required to get wet cotton through the gin without over-drying the cotton near the top of the stack,” says Willcutt. “Module covers are important to keeping seed cotton dry while in modules. Tarps used more than once should be checked for rodent damage, strength and water penetration. Finally, check modules after rain and wind for damaged tarps and for water pooled on tarps.
Valco says it is important to the on-going preservation of lint quality that only clean, dry cotton be put into a module for storage.
“When the aggregate moisture of the seed cotton and foreign matter is 12 percent or less, modules will not heat. Fiber and seed quality will not deteriorate during storage, even for extended periods. Moistures in the 13- to 15-percent range may begin to heat and increase the potential for spotted or light spotted classifications.
“Modules with moistures above 15 percent usually become hot and should be ginned immediately to minimize fiber and seed damage,” adds Valco. “Good management requires module temperatures be monitored during the first five to seven days of storage and that temperatures do not rise more than 15 to 20 degrees F.
Eva Ann Dorris is an ag journalist from Pontotoc, Miss. She can be reached at 662-419-9176 or [email protected].