INTRODUCTIONHave you ever thought about where the clothes you and your family wear come from, or the dressing you put on your salad, or the sheets you crawl under at night before you go to sleep? It comes from cotton! Cotton…the most important and widely used fiber ever known to man. Cotton is used for thousands of things, including clothes, space suits for astronauts and ingredients in the food we eat.
How it is grown, cultivated, harvested and finally processed into cloth and other co-products is what you will be learning about in this story of cotton and Cotton’s Journey - A Field Trip in a Box.
Cotton is a plant, it grows wild in many places on the earth, but it has been known about, cultivated and put to use by people of many lands for centuries.
Scientists and historians have found shreds of cloth or written reference to cotton dating back at least seven-thousand years. The oldest discovery was made in a Mexican cave, where scientists unearthed bits and pieces of cotton bolls and cloth. Archaeologists have also found cloth fragments in the Indus Valley of India (Pakistan) dating about 3000 B.C. In 1500 B.C., cotton was referred to in a Hindu Rig-Veda hymn mentioning “threads in the loom.” It is generally believed that the first cultivation of cotton was in India, though it grew wild in several locations around the world. People living in Egypt’s Nile Valley and across the world in Peru were also familiar with cotton.
Cotton was grown by American Indians in the early 1500’s, documented from sightings by the Coronado expedition 1540-42. The Spaniards raised a cotton crop in Florida in 1556.In England, in the early 1700's, during the height of the British Empire, it was against the law, to either import or manufacture cloth from cotton. These laws were enacted to protect the powerful English sheep and wool industry of that time. These restrictions also kept the cotton industry from expanding to the American Colonies. However, by the early 1600's, cotton had been introduced to North America and in 1607 the first seed was planted by colonists along the James River in Virginia.
The colonists had the ability to produce much cotton but were restricted by the mechanical know-how. It was Samuel Slater, an English mill worker, who changed this by migrating to America in 1790 and building the first American cotton mill from memory. With the development of the cotton mill, Eli Whitney saw the need for a faster means of removing the lint (cotton fibers) from the seed. In 1793, he invented a machine known as the cotton gin. This invention revolutionized the way lint was separated from the seed. Up to that time, for centuries, the separation process had all been done by hand. With Whitney's gin, short for the word engine, lint volume was increased for each worker from 1 lb. To 50 lbs. per day.
Harvesting the cotton by hand was another limitation of productivity. An experienced laborer could pick approximately 450 pounds of seed cotton (cotton removed from the plant with seeds intact) by hand per day. A picking device was first patented in 1850 and a stripper (a machine that strips both open and unopened bolls and trash from the plant) in 1871. In the early 1930’s, after years of development and change, the Rust Brothers of Mississippi used a one row mechanical cotton picker (a machine that used revolving spindles or barbed points to grab and pull the cotton from the open boll) of their design to pick approximately 8,000 pounds of seed cotton in one day. This was quite an improvement in cotton harvest efficiency.
There are several species of “wild cotton” (cotton that grows uncultivated ) in the world. They have been found in Australia, Africa, Arizona, Central America, Lower California, Brazil, Mexico and other tropical countries and islands. Because of problems related to their refinement, they are not economically feasible to use. Through genetic assistance and breeding, today’s cottons have evolved from these “wild” sources and are more processing friendly.
Currently, there are five prominent types of cotton being grown commercially around the world. They are Egyptian, Sea Island, American Pima, Asiatic and Upland. Because of their need for a long, sunny growing period with at least 160 frost free days they are grown between latitudes 45 degrees north and 30 degrees south. The major producing countries within this region are the United States, Peoples Republic of China, India, Pakistan and Republic of Uzbekistan. Also, Brazil, Australia, Egypt, Argentina, Turkey, Greece, Syria and others produce significant, but lesser amount
In the U.S. there are fourteen major cotton growing states that produce Upland cotton. They are Alabama, Arizona, Arkansas, California, Georgia, Louisiana,
Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, Texas and Virginia. Some cotton is also grown in Florida, Kansas and New Mexico. American Pima cotton is grown in Arizona, California, New Mexico and Texas. All of these states form a region in the United States known as the Cotton Belt and have three things in common, lots of sunshine, water and fertile soil, very important to growing a good cotton crop.
Upland cotton being the most common type in the U.S. has a staple length (length of fiber) of 13/16 to 1 ¼ inches. The American Pima has a staple length of 1 5/16 to 1 ½ inches. These plant types grow and mature at different rates and lengths of time, but basically mature within a 30 day period of each other.
Cotton plants have a general time frame in which they grow and produce after planting (introducing the seed to moist soil). With ideal conditions, the planted cotton seed will germinate (to begin to grow) or sprout and emerge in about five to ten days. The first 2 leaves that are visible on the young cotton plant are seedling leaves called cotyledons (cot-a-lee-dons). They are useful for absorbing sunlight into the plant. The sunlight is then converted through a process known as photosynthesis, into nourishing carbohydrates that will help the plant grow.
In about two to four weeks they turn over the photosynthetic task to true leaves (leaves produced subsequent to the cotyledons) which continue the feeding process for the duration of the plants life. The plant continues to grow, adding leaves and height, and in approximately five to seven weeks, small flower buds called squares (a small flower bud covered with fringed leaf-like parts called bracts) will appear on the cotton plant. As this square develops, the bud swells and begins to push through the bracts until it opens into an attractive flower. Within three days, the flower will pollinate (the transfer of pollen from the anther to the stigma of the same or another flower) itself, change from a creamy white or yellow color to a pinkish red, and then wither and fall, exposing a small, green, immature cotton boll (a segmented pod containing 32 immature seeds from which the cotton fibers will grow). This boll is considered a fruit because it contains seeds. As the fibers continue to grow and thicken within the segmented boll, it enlarges until it becomes approximately the size of a small fig. Now, the cotton fibers have become mature and thickened with their primary growth substance, cellulose (a carbohydrate, the chief component of the cell wall in most plants). An average boll will contain nearly 500,000 fibers of cotton and each plant may bear up to 100 bolls
In about 140 days after planting or 45 days after bolls appear, the cotton boll will begin to naturally split open along the bolls segments or carpels and dry out, exposing the underlying cotton segments called locks. These dried carpels are known as the bur, and it's the bur that will hold the locks of cotton in place when fully dried and fluffed, ready for picking.
The growth cycle of the various cotton species vary in length, but the sequence of fruit production remain the same. Weather, insects and moisture can adversely affect optimum conditions for plant growth and it is the farmer's responsibility to adjust to these conditions to optimize yield.
Before cotton can be processed into the many products it becomes. It must be planted, irrigated, nurtured with fertilizer, protected from unwanted weeds, grasses and insects and harvested. This usually means loosening the soil to the depth of 1 to 2 ½ feet with tillage equipment. This will allow water and cotton roots to penetrate the soil and support the plant.
A seedbed (the row in which the cotton seed will be planted) is prepared by listing (forming land into ridges and furrow) the soil. This allows for faster warming of the soil in the spring and directs irrigation water across the field. Small amounts of soil enriching nutrients, such as nitrogen, phosphorus, potassium, may be added to the soil at this time.
Planting may be done by hand, but in the more advanced regions of the world, mechanical planters are used. When the soil reaches optimum temperature, about 65 degrees, these implements will place the seeds in the soil, usually 1 to 2 inches deep, depending on soil type. The mechanical planters can cover as many as 12 rows at a time.
In some cotton production regions, where soil erosion is a problem, conservation tillage is used. In this system, crop residue from the previous crop or a cover crop is left on the soil surface to protect the soil from heavy rains and winds. A special planter is used to open the soil and place the seed without disturbing the protective cover.
As the plants demand it, when available, additional water is delivered to the fields. Sometimes only from natural rainfall, called rain-feed farming, or through irrigation (water application through artificial means), called irrigated farming. This can be accomplished in 3 different ways; 1) furrow irrigation takes place by simply running water down a seedbed furrow, 2) sprinkler irrigation is much like lawn sprinklers where pressurized water is sprayed out over an area, and 3) drip tape irrigation, this is a relatively new method of irrigation using buried tubing that releases water into the soil beneath the plant.
Most of today's commercial cotton farms use a combination of weed control methods. Such as, Cultivation which is done mechanically by machines called cultivators, hand rogueing or weed removal by people with the use of weed hoes and the application of chemical herbicides (chemicals used to control weeds). Chemical herbicides can be applied before or after the cotton is planted. Once the cotton plant has emerged, cultivation and hand rogueing must be done very carefully in order to kill the weeds but not harm the growing cotton plant. If the weeds were allowed to grow, they would compete for nutrients in the soil that are necessary for a healthy and productive cotton plant.
When the cotton plant is in it's seedling stage, it is very susceptible to soil borne fungal disease. There are several diseases that can stunt the growth of the plant, cause leaves to fall off, attack the roots and make the plant wither and die. If the effects of disease don't kill the plant, low yields and a poor quality cotton will result. Development of disease resistant cotton seed has become a priority in the industry. Cotton varieties resistant to some fungi and other destructive organisms have been developed and are being used in certain areas. There is still more research to be done before fungal disease is no longer a factor in producing cotton.
The plant's food, or nutrients, are referred to in agriculture as fertilizer. Nitrogen, phosphorus, potassium, sulfur, calcium and magnesium are the primary fertilizer elements (macronutrients) but there are several trace elements (micronutrients required in small quantities for optimum plant growth) also. These include copper, manganese, zinc, molybdenum, boron, chlorine and cobalt. Starter fertilizer is usually added to the soil before the seed is planted to provide nutrients to feed a healthy seedling. As the cotton plant grows, its nutrient requirement is monitored and any additions needed are applied.
Insect pests have plagued the cotton growing industry over the years and they are a source of constant concern to growers. Insects such as aphid, mite, bollworms, boll weevil, lygus, thrip, White flye, and pink bollworms cause serious destruction to the cotton plants' squares, bolls, leaves, and fiber resulting in a monetary loss to the cotton grower. The pink bollworm is responsible for the most cotton damage and has been found in all of the cotton producing countries, including the United States. The spread of this pest is being held in check by plowing cotton stalks under more than 6 inches deep immediately after harvest to remove over-wintering habitat. There are also beneficial insects or predator insects that feed on various insect pests. Most growers use the services of a crop consultant to monitor their fields for insect pest populations and advise them on treatment. If the insect pest population increases to a level that may severely affect the field's production potential, the grower may then be advised to use an insecticide (a chemical product used to suppress or eliminate an insect pest). These products may be applied by a ground application vehicle specially designed to avoid damaging the cotton plants. Airplanes and/or helicopters are used for air applications, flown low over the field by trained pilots to deliver their load.
A method of insect pest control being practiced on a limited basis is called integrated pest management (I.P.M.). This method coordinates the use of insecticides and the dispersal of beneficial insects purchased to aid in suppressing unwanted insects. Research is being done to find insects to control a wider spectrum of insect pests, a limiting factor of effectiveness in today's I.P.M. practices.
Pest management in cotton production today contributes a substantial share of the costs involved in raising a crop. The cotton farmer is reluctant to treat weed and insect pests unless absolutely necessary to protect crop yield potential. The correct decisions and timing of both irrigations and pest control measures is an ally to a grower's success as he/she guides their crop to maturity.
When enough bolls have opened naturally, harvest aids are applied to the plant to help speed up the maturation process. This, also, is done either by ground or air application. Defoliation helps the leaves to dry and fall off and to help any of the remaining unopened cotton bolls to open. This practice enables the grower to hasten the opening of the cotton bolls which can then be gathered quickly, in a short period of time. It is essential that the crop is harvested before weather and rain can damage or ruin its quality and reduce yield. Frost also causes the plant to shed its leaves naturally and assists in splitting bolls, but may occur too late in the season to benefit harvest. Now the cotton crop is ready to be harvested.
For centuries cotton has been picked by hand. Hand picking is done in the less progressive cotton growing regions of the world. It is very inefficient and no longer practiced in modernized countries.
As the mechanical cotton picker moves through the field, the cotton plants are guided through the picker head (a unit that contains the picking components). The seed cotton, or locks, in the bur encounter revolving barbed spindles attached to a picking bar (a vertical bar that contains 18 to 20 spindles) attached to a rotating drum. The locks are grabbed by the barbed spindle and pulled from its bur. The rotating drum then moves the picking bar toward the doffer. A doffer is a series of curricular, rubber lined pads, stacked 18 to 20 high, that remove cotton from the spindle. The seed cotton and spindles pass through the doffer where the cotton is removed or doffed from the spindle to fall to the picker door (a side component of the picker with channeling to facilitate the movement of cotton). An air vacuum created by a fan then sucks the cotton away from the door and blows it into the basket. The spindle now continues on its rotation passing through the moistener pads (small finned pads stacked 18 to 20 high, which add water and/or moistening agent to the spindles) where they are lubricated to assist in cleaning them. This sequence repeats itself continually while the cotton is being picked. Spindle type cotton pickers harvest most of the cotton grown in the United States.
In some areas of the Cotton Belt, brush strippers are used to harvest seed cotton. These machines remove bolls and burs from the plant with rotating brushes and bats. Material is fed into a field cleaner where much of the burs and sticks are removed and blown into a large basket. They are used primarily in dryland farming cotton areas in Texas where the cotton plant varieties are more compact in stature. Small plant size is important when using a stripper because they tend to accumulate more trash (leaves, bolls, stems and branches) in their harvested product.
Today’s modern cotton harvesters can cover up to 6 to 8 rows at a time and can harvest up to 190,000 pounds of seed cotton a day. These new cotton harvesters are a major improvement over the hand methods of the past.Prior to the development of the module builder, most cotton picked by machines was dumped into cotton trailers and hauled to a cotton gin (a place where seed and fiber are mechanically separated). This system became inefficient when the trailers were filled faster than the gin could process the cotton and the cotton pickers had to cease harvesting while waiting for trailers to empty. This challenge was met with the invention of the module builder in 1972. This implement allows cotton to be dumped from the picker onto the ground and be compressed hydraulically to form a module (tightly pressed stack) of cotton. Each module holds 12-14 bales. This module can be left in the field for storage and later be hauled directly to the gin or transported by a module mover to the gin’s storage yard. The use of these builders allow the pickers to continue harvesting, unimpeded by ginning problems or delays.
PROCESSING THE CROP
The cotton gin is where cotton fiber is separated from the cotton seed. The first step in the ginning process is when the cotton is vacuumed into tubes that carry it to a dryer to reduce moisture and improve the fiber quality. Then it runs through cleaning equipment to remove leaf trash, sticks and other foreign matter.
Ginning is accomplished by one of two methods. Cotton varieties with shorter staple or fiber length are ginned with saw gins. This process involves the use of circular saws that grip the fibers and pull them through narrow slots. The seeds are too large to pass through these openings, resulting in the fibers being pulled away from the seed. Long fiber cottons must be ginned in a roller gin because saw gins can damage their delicate fibers. The roller gin was invented in India centuries ago and this concept is still used in modern gins. Long staple cottons, like Pima, separate from the seed more easily than Upland varieties. A roller gin uses a rough roller to grab the fiber and pull it under a rotating bar with gaps too small for the seed to pass.
The raw fiber, now called lint, makes its way through another series of pipes to a press where it is compressed into bales (lint packaged for market), banded with eight steel straps, sampled for classing, wrapped for protection then loaded onto trucks for shipment to storage yards, textile mills and foreign countries. The cotton industry has adopted a standard for a bale of cotton, 55 inches tall, 28 inches wide, and 21 inches thick, weighing approximately 500 pounds. A bale meeting these requirements is called a universal density bale. This is enough cotton to make 325 pairs of denim jeans.
Every bale of cotton is classed from a sample taken after its formation. The classing of cotton lint is the process of measuring fiber characteristics against a set of standards (grades). Classing is done by experts, called classers, who use scientific instruments to judge the samples of lint. All standards are established by the U.S. Department of Agriculture. Once the quality of the cotton bale is determined, pricing parameters are set and the lint may be taken to market. Cotton marketing is the selling and buying of cotton lint. Cotton is priced in cents per pound when sold and the price is negotiated according to the cotton’s quality. After baling, the cotton lint is hauled to either storage yards, textile mills, or shipped to foreign countries. The cotton seed is delivered to a seed storage area. Where it will remain until it is loaded into trucks and transported to a cottonseed oil mill or directly for livestock feed.
Textile mills purchase cotton and receive the bales from gin yards or cotton warehouses. These mills start with raw bales of cotton and process them in stages until they produce yarn (fibers twisted into threads used in weaving or knitting) or cloth (fabric or material constructed from weaving or knitting).
The first stage is in the opening room. Here, bales are opened and laid in a line on the floor, side by side, near a cotton opening machine. This machine travels along the line of opened bales, pulling fibers to be sent to a mixing machine and then on to the carding system.
Carding is the process of pulling the fibers into parallel alignment to form a thin web. High speed electronic equipment with wire toothed rollers perform this task. The web of fibers is eventually condensed into a continuous, untwisted, rope-like strand called a sliver, (pronounced slyver).
These slivers then continue to a combing machine. Here, the fibers shorter than half-inch and impurities are removed from the cotton. This process makes the sliver smoother so more uniform yarns can be produced. The drawing or pulling of this sliver is next.
The sliver is drawn out to a thinner strand and given a slight twist to improve strength, then wound on bobbins (spools wound with the thread-like product for storage). Having completed this process, it is now called roving. The roving bobbins are now ready for the spinning process.Spinning is the last process in yarn manufacturing. Today's mills draw and twist the roving into yarn and place it on bobbins. They do this quite efficiently. A large, modern mill can produce enough yarn or thread in 30 days to wrap around the earth 2300 times or go to and return from the moon 235 times. With the use of automatic winding, the yarn bobbins are transferred to larger bobbins called cheese cones. These cheese cones can be stored until they are needed in the weaving process.
The weaving process uses yarn that, depending on how it lies in the woven goods, now assume different names. These yarns may now be either a warp or a weft yarn. Warp refers to yarns that run lengthwise in woven goods. In preparation of warp yarns for weaving, hundreds of yarn strands are wound from cheese cones onto a large warp beam. Yarns on this beam are then coated with a sizing compound (a starch mixture) to add strength for weaving. The sized yarns are then wound onto a loom beam that will be placed on the loom (a machine used to interlace yarns to form cloth). Weft is the yarn that runs crosswise in woven goods and may be referred to as filling yarn. Sizing is not placed on weft because flexibility is needed in the weaving process. In today's most modern mills, the weft is fed into the loom from cheese cones with air-jets at such a high speed that its movement cannot be seen.
The woven cloth from the loom, called greige or grey, is whitish but has a natural yellow tint. This cloth is further treated by various means to improve its appearance and feel, then either bleached, dyed or printed to produce the fabrics used in various products seen on store shelves.
There are three basic weaves that are used. The plain weave, the most common, is produced by passing the weft yarn over and under each warp yarn, alternating each row. This is used for cotton print cloth, sheeting, muslin and more. The twill weave is produced by interlacing yarns in an angle to form straight, diagonal ridges across the fabric. This is used for sturdy products such as denim, gabardine and ticking. The satin weave, has a surface that consists mostly of warp yarn which is passed over and under all but one weft yarn that intersects in a regular or irregular formation, not a straight line. This weave produces a fabric with a smooth surface. It is used for upholstery, home decorating and fashionable apparel.
Knitting is another method of turning yarn into fabric. Knit fabric is constructed of yarns made into loops (stitches) which are linked together by the use of needles. There are two basic types of knitted fabric. The weft knit fabrics are made with yarns forming loops the width of the fabric on a circular machine, producing jersey knit used in T-shirts and underwear. The warp knit fabrics are produced by feeding yarns to form loops in a lengthwise direction and are used for tricot fabrics and cotton lace. Knitted fabrics are softer and more flexible than woven fabrics. Making them ideal for sweaters, active sportswear and hosiery.
Cottonseed mills, in the late 1800’s, used manual powered mechanical pressure to squeeze the oil from the seed. This was very labor intensive and at best recovered only one-half the oil contained in the seed. Today's mills are either screw press or solvent extraction types. The oil is removed from the meats leaving only 1-2 percent oil in the meats. With the production of 790 lbs. of cottonseed per bale of cotton lint, modern mills can extract 140 pounds of cottonseed oil. This essentially doubles the oil production efficiency of the older mills.
Processing of cottonseed in modern mills involves a number of steps. The first step is its entry into the shaker room where, through a number of screens and air equipment, twigs, leaves and other trash are removed. The cleaned seed is then sent to gin stands, similar to those in cotton saw gins, where the linters are removed from the seed (delinted). This linter removal process is usually done twice and the fibers are collected and pressed into 600 pound bales. The linters of the highest grade, referred to as first-cut linters (longer more resilient fibers) are used in manufacturing non-chemical products, such as medical supplies, twine, and candle wicks. The second-cut linters (short fibers or fuzz), removed in further delinting steps, are incorporated in chemical products, found in various foods, toiletries, film, and paper.
The delinted seeds now go to the huller. The huller removes the tough seed coat with a series of knives and shakers. The knives cut the hulls (tough outer shell of the seed) to loosen them from the kernels (the inside meat of the seed, rich in oil) and shakers separate the hulls and kernels. The kernels are now ready for oil extraction and the hulls are sent to storage to be sold for livestock feed. Some industrial uses for hulls have been developed and are being tested. A plastic containing hulls as a major ingredient has been used in producing small parts for textile machinery. Hulls are often incorporated in the mud used in oil well drilling. They are also used in the production of synthetic rubber and in petroleum refining.
The meats (kernels) are now prepared for oil extraction. They pass through flaking rollers made of heavy cast iron, spinning at high speeds. This presses the meats into thin flakes. These flakes then travel to a cooker where they are cooked at 170 degrees F to reduce their moisture levels. In screw press mills, the kernels flow directly into a press which has a screw or worm gear revolving inside a horizontal steel barrel. This meat grinder type action exposes the flakes to extremely high pressure, 10 to 12 tons per square inch, forcing 96% of the oil from the meats. In the solvent extraction mills, the cooked meats are flaked to about the thickness of paper and exposed to live steam and high pressure. This action ruptures the oil cells making the oil accessible for the solvent extraction process.
The prepared meats are conveyed to the extractor and washed with hexane (organic solvent that dissolves out the oil) removing up to 98% of the oil. This hexane-oil mixture is called miscella. The miscella is pumped out of the extractor and is distilled by boiling the hexane from the mixture and condensing it with cooling water. The hexane is reused over and over again. The crude cottonseed oil is then ready for further processing and the de-oiled meats are subjected to live steam for removal of residual hexane. The meats are then dried and ground to produce a 41% protein livestock feed, called cottonseed meal. Cottonseed meals' major value is the high protein it contains to build muscle, nerve, blood and hair. A small amount of cottonseed meal is used for fertilizer. Its organic matter improves soil texture and reduces watering needs.
Crude cottonseed oil requires further processing before it may be used for food. The first step in this process is refining. With the scientific use of heat, sodium hydroxide and a centrifuge (equipment used to separate substances through spinning action), the dark colored crude oil is transformed into a transparent, yellow oil. This clear oil may then be bleached with a special bleaching clay to produce a transparent, amber colored oil. Upon further processing, the oil is deodorized or treated so it will remain clear and have no unwanted flavors.
Cottonseed oil is used in several products. Depending on its stage of refinement, it can be used in snack foods, mayonnaise, margarine, baking or frying oils, explosives, cosmetics, rubber, soap, insecticides and many other products. Foodstuff cottonseed oil has superior nutritive qualities and is on the American Heart Association's list of "okay foods".
Although fiber is the most valuable product from a cotton field, it is important to remember that this versatile plant also provides many products for human and animal consumption. It is from this perspective that cotton becomes a food crop.
THE COTTON INDUSTRY AND YOU
The cotton industry is constantly striving to develop new and improved methods for producing quality products at a reasonable price. The cotton industry continues to look toward the future at further improving their product while providing employment opportunities for millions of people in a variety of related areas.
Cotton related job opportunities can be found from the farm where the cotton is produced to the department store where the garments are sold. Cotton supports the dairy industry by providing a source of food for the milk cows.
Cotton seed can be processed to produce oil for cooking and blending with food products. Jobs can be found in the trucking and transportation industry as it is often transported thousands of miles from the cotton gins to the cotton mills, and then again to the distribution outlets.
Transforming the cotton boll through the processes of delinting and cleaning at the gin to processing at the mill for spinning and weaving fabric requires a trained labor force. The dying of fabric and the assembly of clothing and other products can provide employment for many. High quality papers requiring cotton and paper mills employ thousands annually. The fashion industry needs trained individuals to select the proper combination of fabrics and design to market them to the public. Fashion models rely on these products in their profession. The cotton industry continues to find new and improved uses for cotton worldwide and the public fuels continuous demand for this important commodity. With cotton having all these uses and benefits,it has certainly lived up to the name it was given years ago....."white gold."