Problems of Machine Picking

Ralph A. Rusca, Charles A. Bennett.

Power machines have lowered the cost of producing cotton, but they have also created new problems at the gin and the textile mill.

Machine-picked cotton contains extra moisture from the spindles and considerably more than the usual 5 to 15 percent of trash present in hand-picked cotton; particularly bothersome is leaf material, one of the most difficult types of trash to remove.

The additional moisture and trash in machine-harvested cotton frequently complicate ginning and raise the costs of textile manufacture by calling for extra cleaning steps at the mill. Yet the industry recognizes that mechanical harvesting is an essential step in the mechanization of cotton production to reduce over-all costs to levels comparable with those of synthetic textile fibers.

The actual percentage of the total American cotton crop picked by machines is small. The National Cotton Council put it at 16 percent for the 1950 crop. On the basis of a total crop of nearly 10 million bales, that means that about 1.6 million bales of machine-picked cotton were available. The significant fact is that this number is an increase of 75 percent over the 1949 estimate. The limiting factor in mechanical harvesting has been not so much the unwillingness of cotton farmers to use mechanized equipment as it has been the lack of machines. With availability of machines and mechanical improvements a certainty, machine-picked cotton is bound to be reckoned with more and more as time goes on.

MACHINES USED to harvest cotton are of two general types spindle pickers and strippers. Varying designs of each are on the market.

The present spindle picker was evolved from a machine believed to have been first patented in 1850. Today's models are high-wheeled motorized vehicles, which straddle the cotton row during picking. The revolving spindle is designed to remove the cotton from the boll with a minimum of entanglement with the plant. Operation of this type of picker has recently been improved by application of chemical wetting-agent solutions to the spindles to reduce the amount of moisture transferred from the spindles to the fibers below the amount transferred by former methods, which used large quantities of water alone.

The mechanical stripper in common use operates on a principle whose first application to harvesting was recorded in 1871. The original design was a large boxlike body, or sled, which was pulled along the row so that the cotton plants extended through finger-type projections in front. Modern units have the fingers mounted separately on the side of a tractor, with a built-in conveying system to discharge the cotton into a trailer, which the tractor pulls. The stripper, in contrast to the spindle picker, removes everything from the plant but the upright stalk and heavier branches.

The efficiency of either type of machine is affected by cultural practices. With strippers, varietal characteristics are especially important. Spindle pickers are satisfactory for harvesting a wider range of cotton varieties than strippers, but because the strippers cost less they tend to be used even where the varieties grown make them unsuitable.

THE COTTON that the farmer brings to the gin continues to belong to him. His acre yield will be calculated from the amount of lint actually ginned. The quality of the baled cotton will determine the price he will receive. During just the few minutes it takes to gin a bale of cotton, the marketable values of the lint can be vitally affected. From the farmer's standpoint, therefore, poor ginning of his crop may nullify any advantages he has had in producing it.

The specific problems in any locality in ginning mechanically harvested cotton arise from many variable factors regional production, variety of cotton, skill of labor, type of machine used in the harvest, and other conditions that contribute to the market qualities and end uses of the cotton.

An example of variables in regional production: Objectionable growths of grass are seldom found in cotton fields of the Southwest, where varieties of shorter staple length are grown and more mechanical strippers than spindle pickers are employed for harvesting. But in the Central and Southeastern States, where the cottons have somewhat longer fibers and spindle pickers are more popular and feasible, it is more likely that grass will tangle with the fibers and so increase the difficulties of cleaning at the gin.

Many farming practices that affect the efficiency of mechanical harvesting the cotton variety, the method of picking correspondingly affect the efficiency of ginning. The manner of transporting and the nature of storage before ginning also make special demands upon ginning facilities.

The purpose of ginning was once only to separate the seeds from the cotton fibers, but the process has been expanded through the years to include the service of improving the quality of the ginned lint. More recently, additional cleaning steps have been introduced to meet the requirements of mechanically harvested cottons.

Gin operations today begin with storage of seed cotton, when necessary, on the premises or at the gin. Thereafter they proceed in this order: Drying the seed cotton; screening out the smaller particles of trash; extracting pieces of foreign matter too large to be screened out (sticks, stems, leaves, and hulls) ; feeding the cotton into individual gin stands; the ginning proper (separating the fiber from the seed by the saws) ; conveying the fibers by air to the press box; and, finally, packaging, or baling, the fiber. The ginned seed is usually conveyed to a seed-storage house or returned directly to the farmer's wagon or truck.

A recent development to which the Department's Cotton Ginning Laboratory has contributed is a lint-cleaning process introduced between the gin stand and the press condenser. As much as half a grade in quality has been gained by the extra cleaning at this point. Several ginning-machinery manufacturers now sell lint cleaners to cotton gins, and more than 2.5 million bales have been handled to date through them, seasons 1948-49-50.

Bulk storing of seed cotton on farms or at gins is particularly necessary in mechanical harvesting, where the speed of gathering exceeds that of ginning. Older forms of storage seldom benefit cotton after a week, especially moist cottons from mechanical harvestings. The Department is conducting research to develop better methods of handling mechanically harvested cottons in storage, with the thought that the storage period may be turned into an asset for the industry.

A new system under study is based on drying and cleaning the seed cotton before storage, and then, if necessary, drawing air through a series of bins in which the cotton is stored. With this arrangement, the cotton can be processed and aerated on its way in or out of storage or after it is in the bins.