Dry seasons over the past four years have generated quite a bit of interest in adding moisture back to dry cotton, according to Stanley Anthony and David McAlister.
But the potential advantages come with drawbacks, they said at the summer conference of the Southern Cotton Ginners Association at Franklin, Tenn.
Both have done research into the feasibility of the practice.
Anthony, who is supervisor of the USDA Agricultural Research Service Cotton Ginning Laboratory at Stoneville, Miss., cited studies going as far back as 1957, when researchers added water to cotton bales before packaging, and found that high moisture levels in flat bales covered in jute bagging resulted in damage from mildew/fungus after 70 days storage.
In a more recent study, varying amounts of moisture, ranging from 0 to 55 pounds per bale, were sprayed on top of cotton as it came down the lint slide. Moisture content of the bales after water was added and before storage ranged from 6 percent with no overspray to 15.4 percent for the highest amount of water added.
“There were large fluctuations in moisture distribution for the high-moisture bales, because the bales were still seeking equilibrium,” Anthony noted, “while moisture in the low-moisture bales remained basically steady.”
After 116 days of storage, the bale with no water added remained at about 6 percent moisture content, while all the other bale moistures had changed, even though they were triple-sealed in polyethylene bags.
“Above 8 percent, we began seeing problems, regardless of the bale covering,” Anthony said. These included reductions in color and increases in microbial activity.
Short fiber content and neps appeared to increase at higher moisture levels and HVI color decreased from Middling (31) to Strict Low Middling Spotted (43) as moisture content rose from 6 percent to 15.4 percent.
Reflectance and yellowness values indicated the bales became darker and more yellow as moisture increased.
Because of these adverse changes, “I think we have to be very careful in adding water to cotton,” Anthony said. “Somebody would end up having to eat some of it.”
In other ginning developments, he said a computerized process control system now being used by some gins can improve fiber quality and return additional income to the grower.
“Approximately 1.8 million bales were ginned on this equipment in 2001,” Anthony said, “and approximately 70 gins will be using it this season, with perhaps a 2 million-bale volume. This technology can go a long way toward boosting farmer profits — $8 per bale on average — and reducing ginning costs.”
David McAlister, research leader at the Clemson, S.C., Cotton Quality Research Station, said wide variations in moisture content affects the strength and evenness of yarn spun from the cotton, as well as spinning efficiency.
In a study in cooperation with mills, he found that when cotton fiber is allowed to reach equilibrium in a controlled humidity environment, it gains additional strength, resulting in fewer yarn breaks.
“This equates to real money for the mills by avoiding expensive production shutdowns,” he said.
“There is an obvious relationship between moisture content and yarn strength; 6 percent to 6.5 percent is optimum. Higher than that, there are complications and you'd risk discounts.”
The problem, McAlister said, is that “mills don't have the luxury to open and adequately condition the cotton ahead of use. This conditioning takes at least 72 hours, whereas the mills have only about 18 hours at most.”
His conclusion: “If moisture's going to be added to cotton, the gin's the logical place to do it because mills don't have the infrastructure to provide the needed holding time.”
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…adding water at gin can boost profit
“THERE'S POTENTIAL to put extra money in every bale — and in the grower's pocket” by adding extra water during ginning, says Southern Cotton Ginners Association consultant Bill Mayfield.
“In my opinion, in a perfect world, every bale would leave the gin with a 7 percent to 8 percent moisture level,” Mayfield, an engineer and former USDA Extension cotton specialist, told northwest Mississippi ginners at an SCGA meeting at Clarksdale, Miss. “But in reality, most are probably only in the 4 percent to 6 percent range.”
Saying “I'm a very strong proponent of moisture restoration,” he cautions ginners, however: “Don't count on improving quality by adding moisture, because it won't happen. The decision should be made on the basis of adding pounds, and the moisture level should not exceed 7.5 percent to 8 percent to avoid problems with grade/color loss.”