cotton

Harvesting cotton in Lost Hills, California, USA, an area that took up cotton growing during the 1940s and 1950s as irrigation techniques improved. The USA remains the world's largest producer of cotton, although in recent decades the market for cotton has seriously declined in the face of huge competition from synthetic fibres.

Harvesters on a cotton plantation in Lost Hills, California, USA. Cotton is the fourth largest crop in the US, grown mainly in the states of Louisiana, Mississippi and Alabama. In California, cotton is generally grown using irrigation.

Detail of a cotton seed head, showing the ball of fibre which surrounds the actual seeds. The ‘boll’ has ripened, and the fibres are tumbling out.

Harvesting cotton in California. Cotton is picked as soon as the bolls (the seed pods that produce the cotton fibre) mature and open. Harvesting is done both by mechanical means and by handpicking; the latter results in a higher yield, as it is possible to collect only the mature bolls.

A cotton mill, c.1850. Cotton was spun and woven into cloth by hand in England until textile machinery, developed in the late 1700s, revolutionized its manufacture and provided an impetus for the Industrial Revolution. By the mid-19th century, cotton manufacture was an entirely factory-based operation, notably in the Lancashire towns of Manchester and Oldham.

Tropical and subtropical herbaceous plant belonging to the mallow family. (Genus Gossypium, family Malvaceae). Fibres surround the seeds inside the ripened fruits, or bolls, and these are spun into yarn for cloth. Cotton fabric is cool and comfortable to wear, resilient, absorbs moisture, is light, washes easily, and dyes well, but can crease quite badly.

The fibres are separated from the seeds in a machine called a cotton gin. Individual fibres can measure up to 6 cm/2.4 in long. The seeds are used to produce cooking oil and livestock feed, and the pigment gossypol may be useful as a male contraceptive in a modified form. Cotton disease (byssinosis), caused by cotton dust, can affect the lungs of those working in the industry. The cotton plant is very susceptible to disease and cotton production uses 50% of world pesticides while representing only 5% of world agricultural output. However, advances in genetic engineering led to the development and trial of a cotton plant genetically modified to contain the Bt gene, which produces an insecticidal toxin. Although controversial, the modified plants led to an 80% decrease in organophosphate pesticides.

Improvements in synthetic fibre mean that it is sometimes used instead of cotton. Different areas produce different qualities of cotton. Egyptian cotton fibres are usually very fine and long, whereas Asian cotton fibres are shorter and coarser. Very short fibres (cotton linters) are used in the production of regenerated synthetic fibres.