Nature of Cotton
Botanically, three principal groups of cotton are of commercial importance. The first, the species Gossypium hirsutum, is native to Mexico and Central America and has been developed for extensive use in the United States, accounting for more than ninety-five percent of U.S. production. This group is known in the United States as “American Upland” cotton and has fibers that range in length from about 7/8 to 15/16 inches. The second botanical group, the species G. barbadense, which makes up the balance of U.S. production, is of early South American origin. With fibers ranging in length from 1¼ inches to 19/16 inches, it is known in the United States as “American Pima” cotton, also commonly referred to as “Extra-Long Staple” cotton. A third group, G. herbaceum and G. arboreum, consists of cottons with shorter fiber lengths, ½ to 1 inch, that are native to India and Eastern Asia. No cottons from this group are grown in the United States.
A single pound of cotton may contain 100 million or more individual fibers. Each fiber is an outgrowth of a single cell that develops in the surface layer of the cotton seed. During early stages of its growth, the fiber elongates to its full length as a thin-walled tube. As it matures, the fiber wall is thickened by deposits of cellulose inside the tube, leaving a hollow area in the center. When the growth period ends and the living material dies, the fiber collapses and twists about its own axis.
The term “cotton classification” in this publication refers to the application of official standards and standardized procedures developed by USDA for measuring those physical attributes of raw cotton that affect the quality of the finished product and/or manufacturing efficiency. USDA’s classing methodology is based on both grade and instrument standards used hand-in-hand with state-of-the-art methods and equipment to provide the cotton industry with the best possible information on cotton quality for marketing and processing. USDA classification currently consists of determinations of fiber length, length uniformity, fiber strength, micronaire, color, trash, leaf, and extraneous matter.
The system is rapidly moving from reliance on the human senses to the use of high-volume, precision instruments that perform quality measurements in a matter of seconds. Only the classifications for extraneous matter and special conditions are still performed manually. Research and development continue for the technology and instrumentation to rapidly measure extraneous matter, as well as other important fiber characteristics, such as maturity, stickiness, short-fiber content, and neps. USDA will complete the transition to an allinstrument classification as quickly as the technology can be developed and instruments are sufficiently refined to assure representative and reliable quality measurements.
Practically all cotton grown in the United States is classed by USDA at the request of producers. Although classification is not mandatory, growers generally find it essential to marketing their crop and for participation in the USDA price support program. The USDA AMS Cotton and Tobacco Program operates ten cotton classing facilities across the Cotton Belt (their locations are shown on the map on the inside back cover of this booklet). These facilities, which are part of Grading Division, are designed specifically for cotton classification and are staffed exclusively with USDA personnel.
USDA also classes all cotton tendered for delivery on futures contracts on the Intercontinental Exchange and provides arbitration classing to the industry. These services are performed by the Quality Assurance Division. Classification services are also provided to individual buyers, manufacturers, breeders, researchers, and others upon request. All users of USDA classification services are charged fees to recover classification costs.
At the gin, cotton fibers are separated from the seed, cleaned to remove plant residue and other foreign material, and pressed into bales of approximately 500 pounds. A sample of at least 4 ounces (115 grams) is taken from each side of the bale by a licensed sampling agent and identified with a Permanent Bale Identification (PBI) tag. The total 8‑ounce (230‑gram) sample is delivered by the agent or a designated hauler to the USDA classing facility serving the area. Gin and warehouse operators serve as licensed sampling agents and perform this function under USDA supervision.
Upon arrival at the classing facility, the samples are conditioned to bring the moisture content into a specified range before the classing process begins. The samples are then transported to the instrument-testing and manual-classing stations, where classification is performed. Remnants of the samples used during the classification process are baled and sold by USDA, with the proceeds applied to offset classification costs.
Once classification is complete, the fiber measurement results are immediately available to the customer from the classing facility’s database. Providing cotton quality results quickly gives producers and buyers access to crucial information at the time of sale. At the peak of the season, USDA classes and provides data on as many as two million bales per week nationwide.
The PBI system allows cotton to be tracked from the field to the classing office. On the field, each cotton module is labeled with an identification number that links it to the producer, field, and seed variety. At the gin, each module identification number is logged into a database, and each bale is labeled with a PBI tag with a twelve-digit number and barcode identifying the classing office, gin, and bale. Samples taken at the gin for classing also are labeled with PBI tags.
At the classing office, the PBI tag follows the sample through testing. The results are linked to the bale and stored in the USDA AMS Cotton and Tobacco Program’s National Database by PBI number. The classification data in the National Database can be accessed by the owner of the cotton or the owner’s authorized agent. Users of this system include grower marketing cooperatives, buyers, and textile manufacturers.