Cotton

Cotton

Scientific Name Gossypium sp.
Common Names English: Cotton; German: Baumwolle; Spanish: Algodón; French: Coton

Occurrence

Agriculture Importance

The global area planted to cotton happens to fluctuate between 31 and 35 Mio. hectares. The total annual production averages around 25 Mio. tons.. India traditionally accounts for about 1/3 of the total area and has become the biggest producer. Other leading countries are China, USA, Pakistan, Brazil and Uzbekistan, the USA being the most important exporter. In many developing countries, cotton is of crucial importance for the national economy as a cash crop for export. Of the whole cotton harvest, more than 90% is 'upland cotton' (Gossypium hirsutum), the rest mainly belonging to ELS (Extra Long Stable) cotton (G. barbadense). The two other species, 'levant cotton' (G. herbaceum) and 'Indian cotton' (G. arboreum) are of minor importance.

Crop Management

for Cotton:

Cultivation

While naturally perennial and capable of growing to heights of 6-20 m (19.7 - 65.6 ft), cultivated cotton is planted anew each year. It requires deep and well drained, thoroughly cultivated, crumbly soil and a lot of water - about 100 mm (0.39 inch) precipitation per month or equivalent irrigation - but it cannot withstand high humidity or heavy rains. The plants tolerate light salinisation, but they are sensitive to frost. Ample insolation is important, especially for seedlings. Shade, or even prolonged overcast weather, will lead to reduced flower formation and increased shedding of bolls. Depending on local climate and the cultivar planted, the time between sowing and clearing is about 180-220 days.

Flowering begins when the plants are about 8 weeks old, and continues for over six weeks. The development time from flower to opening boll is ca. 8 weeks. Pickings may stretch over a period of f 6-8 weeks. Even today, much cotton is still hand-picked, which is a very labor-intensive process. Nevertheless, machine harvesting is only used where human labor is expensive, because it causes significant quality losses due to the rough treatment of the gathered cotton. Depending on the method, it may also require plants to be defoliated before harvest, either by frost or by chemicals. Of the harvested produce, cotton fiber (lint) accounts for 33% to 45%, the rest are seeds. Avergae yields of lint may be as low as 200 kg/ha (e.g. some African countries), or even exceed 2.000 kg/ha (Australia). The world average is about 800 kg / lint / ha.

Cultivation Areas

The genus Gossypium is for the most part pan-tropical. Cotton requires a warm, dry climate (optimum temperature: 25-35°C; 77 - 95°F) for its cultivation, and a frost-free period of ~200 days is essential. It is grown from 47º N (in the Ukraine) to 32º S, and at elevations of up to 1,500 m (in Africa). Production occurs worldwide in more than 80 countries, but China, the USA and India together account for more than half of the cotton produced. The highest yields are achieved under irrigation in desert climates. In some countries, the enormous water consumption for irrigated cotton fields has led to significant ecological problems.

Special Information

Cotton is the most important one among natural fibers. Cotton contributes 1/3 to world’s fiber consumption, today dominated by synthetic fibers.

Textiles made from cotton were already known in the prehistoric cultures of both the New and the Old worlds. Apparently, the cultivation of Gossypium species has at least two independent geographical origins. The oldest cotton fabric was found in Tehuacán (Mexico) and dated to about 5800 BC. Another find, dating from about 3200 BC, was made at Mohenjo-Daro on the banks of the lower Indus in modern Pakistan. The earliest evidence for the cultivation of cotton in Egypt is from 500 BC.

At about the same time (445 BC), it was mentioned by Herodotus as an Indian plant. In the Roman Empire, cotton soon started to be traded on a large scale, beginning in the 4th century BC. During the Middle Ages, Arab conquests brought it to Spain and northern Italy. The origin of the cotton species cultivated in North America is not quite clear. It is very likely, however, that Spanish settlers from Mexico introduced upland cotton (G. hirsutum) to the USA in around 1700 AD, following domestication by pre-Columbian civilizations in Mesoamerica. Sea-island (ELS) cotton (G. barbadense) originates from tropical South America, G. arboreum from Asia, and G. herbaceum from Africa, where it can still be found growing wild in some places. While the American species are tetraploid, those from the Old World are diploid. Nowadays, one of the major objectives in breeding is to achieve even and early ripening of the cotton capsules. In the USA, varieties have been selected that can be harvested after just 135 days. Another important goal is to improve resistance to pests, since cotton plants are very susceptible to insect attack.

Taxonomy

Family

Malvaceae. Commercially-grown cotton usually belongs to one of four different species: Gossypium herbaceum, G. hirsutum, G. barbadense and G. arboreum. Each of them has numerous subspecies and varieties. G. hirsutum (also called upland cotton) is by far the most widely used.

Use

Food

Cotton seeds contain up to 25% oil. The main component is linoleic acid, which makes the oil a widely-used raw material for margarine and shortenings. However, to be usable for nutritional purposes, cottonseed oil must be refined, mainly to remove the toxic polyphenol gossypol.

Fodder

The seeds that are a by-product of oil extraction are fed to livestock as 'cotton cake'.

Industrial Products

In spite of the emergence of synthetics during the 20th century, cotton still accounts for nearly 40 percent of total yarn production worldwide, making it the most important raw material for the textile industry. Its cellulose fibers are valued for their strength and their ability to absorb moisture (water absorption capacity 65%). The short fibres produced during harvesting and ginning are used in the production of artificial silk (cellulose acetate), explosives, paper, upholstery and insulating materials. In ancient times, cotton was considered a very valuable fabric, due to its labour-intensive production. This changed radically with industrialization: in 1641, the first European cotton-spinning factory was founded in Manchester, UK. During the 18th century, numerous inventions laid the foundation for modern mass production of textiles.

Each cotton seed has 2,000 to 7,000 fibrous hairs. In order to obtain spinnable fibres, this 'lint' has to be separated. Since 1793, this has been done with 'gins' (i.e. deseeding machines).
Cotton quality is classified by the length of the lint. 'Very short staple' (<16 mm; <0.62 inch) and 'short staple' (16-24 mm; 0.62 - 0.94 inch) are gained from G. herbaceum and G. arboreum. They are mostly grown for oil for local use only, and are rather drought-resistant.

'Medium staple' (25-28 mm; 0.98 - 1.09 inch) is produced from G. hirsutum; 'long staple' (29-33 mm; 1.13 - 2.97 inch) from some G. hirsutum cultivars and G. barbadense; 'extra-long staple' (>35 mm; >1.36 inch) only from G. barbadense, whose lint can be up to 60 mm (2.36 inch) long. Low-grade cottonseed oil is used for the production of soaps, lubricants and paints. Seed hulls and dry stalks are used as a fuel.

Facts on selected crops