Crop Profile: Cotton - (Gossypium spp.)

Cotton (Gossypium arboreum L./ G. hirsutum L.)is the most important fiber crop grown globally. Cotton provides raw material for the textile industry. Cotton is the name derived from Arabic Al-qutn. In botanical terms, cotton is the soft, fluffy staple fibre that is produced around the seed in the protective boll of genus Gossypium. The fibre is botanically meant for the dispersal of seed. The fibre is almost pure cellulose. 

HISTORY

1. The cultivation of cotton has been reported as old as 5000 BC in the western Pakistan, for example, the Mehrgarh excavation showed cotton fibres preserved in copper beads. The cultivation then spread in the Indus Valley Civilization. 
2. Evidences about the cultivation of cotton in Iran (pre-islamic Persia) also exists which dates back to almost 5th Millenium BC. From these regions, the cotton was taken to the Europe and other continents. 
3. By the end of 16th century BC, cotton was being cultivated in most of the warmer regions of Asia and Europe. 
4. During the British rule of sub-continent, the cotton processing in India was greatly reduced and Indian raw cotton was exported to Britain for processing and thus the Indian farmers suffered a lot. This was the time of great industrial revolution in Britain. 

5. During 1840s the production suffered a decline, the cotton processing industry also suffered from it, but then recovered due to development of long and strong fibre, American cotton.
6. Today, American cotton occupies 90% of the world market. 

In 1901, the Peru cotton fields were destroyed by Fusarium wilt which dried up the entire cotton plantation. 

TYPES OF COTTON

Four types of cotton are being cultivated 

 i- Gossypium hirsutum: 20% of world production - native to Central America, Mexico, the Caribbean and the southern Florida.

 ii- Gossypium barbadense: 8% of world production - extra-long staple cotton, native to tropical South America

iii- Gossypium arboreum: 2% of world production - native to Pakistan and India

iv- Gossypium herbaceum: less than 2% of world production - Levant cotton, native to southern Africa and the Arabian Peninsula.

PLANT CHARACTERISTICS

The plant is a shrub, native to tropical and sub-tropical regions of the world. The plant consists of an erect, woody and circular main stem with a number of lateral branches. It has a strong tap root system, which penetrates deep into the soil up to 200 cm. The growing point in at the apex of the stem with an apical bud like in most other dicots. When the apical bud is active, the lateral bud below remains dormant. The main stem carries branches and leaves but no floweres. The lower branches at the base of the stem are vegetative (i.e., monopodial), while the upper branches are reproductive, fruit bearing (i.e., sympodial). Cotton leaves are large and hairy with 5 to 7 lobes. The fruit is a "boll" or capsule, which consists of 2 - 6 locules. each containing a number of seeds. The boll opens at maturity, yielding a fluffy mass of fibre called 'lint' and seeds. The seeds account for 65-70% by weight of the total yield. The colour of seed may be brown or black. The seeds contain 15% protein and about 25% oil. 

ADAPTATION

Cotton is a tropical/subtropical crop, grown in kharif season. It requires a frost-free season of at least 180-200 days, heavy sunlight, and summer temperatures of 26-30^oC with optimum water supply. Loam or clay loam which allow root penetration are best soils for cotton crop. pH should be 6.0-8.0, hence cotton grows well on alkaline soils of Pakistan. Saline and waterlogged soils are unfit for cultivation of cotton. 

Bt COTTON

Cotton is attacked by a number of insect pests which mostly attack the boll thus reducing the economic yield of the crop. Hence genetically modified (GM) cotton was engineered to combat the particular group of insect pests naturally. The bacterium Bacillus thuringiensis naturally produces a chemical which is toxic to a particular fraction of insects which are larvae of moths, butterflies, flies and beetles, but harmless to other forms of life. The gene coding for this toxin is genetically engineered into the cotton and so obtained cotton has naturally produced insecticide in the plant body. In this way, the need for pesticide sprays has been largely reduced in areas where Bt cotton is cropped. 

But on the other side of this, the secondary pests mostly plant bugs, stink bugs and aphids are not controlled by Bt cotton and they require pesticide spray for control which reduce the effectiveness of genetically modified cotton to some extent. But the incidence of secondary pests is dependant on the environment and climate of the particular site. 

International Service for the Acquisition of Agri-Biotech Appliance (ISAAA) has reported that in 2009, Bt cotton covered 49% of the total world crop area, where Australia had highest area 95% under Bt cotton cultivation, USA had 93% and India had 83%.

OTHER GENETIC MODIFICATIONS

Gossypol is a toxin produced by the cotton which makes it inedible. Scientists have also genetically silenced the gene responsible for this chemical thus making it edible crop.

Glyphosate is a broad-spectrum herbicide sold by the name of Roundup by Monsanto. The same company has now introduced the seeds of GM cotton resistant to this herbicide.

ORGANIC COTTON

There is much more popularity of organic farming in the world. The term organic cotton means the crop which is not produced from genetically modified cotton seed nor it has been given any chemical treatment at any stage from sowing to harvesting. 

IMPORTANCE OF COTTON

Cotton serves as multipurpose crop. Though the major use of cotton is for its lint, but cotton seed is also used for oil extraction as well as the wood of cotton is used for fuel purposes. In 2010-11, world cotton production was estimated to increase to 113.9 million bales from an area of 32.5 million hectares which is 7% more from the previous year 2009-10. In 2010-11, China was the leading producer of cotton with33.0 million bales followed by India with 27.0 million bales, Russia with 18.0 million bales and Pakistan at fourth place with 10.3 million bales. Where as the five major exporters in 2011 are i) U.S.A, ii) Brazil, iii) India, iv) Australia and v) Uzbekistan. The total international trade is estimated to be $12 billion.

In Pakistan, cotton is cultivated in Punjab and Sindh province. Pujab has major share in production of cotton with Multan, Melsi and Bahawalpur as the dominant areas of cotton prouduction. Faisalabad is the textile hub of Pakistan.

COTTON IN TEXTILE AND FABRIC INDUSTRY

In addition to the creation of several different fabrics, including denim, corduroy, twill and flannel, cotton is used to make fishnets and reusable coffee filters. Cotton’s versatility, durability and utility have led to entire sectors of the fabric industry being entirely dependent on it, although this dominance has diminished in the age of synthetic fabrics. Cotton as Food, Medicine, and Paper.

BY-PRODUCTS OF COTTON

Cottonseed oil and cottonseed meal are by-products of the ginning process; the invention of the cotton gin, which permitted mechanical separation of the cotton boll, opened the door to economically practical use of cotton. The oil and meal are edible; the former can be used in cooking, while the latter is generally fed to livestock. In addition, cotton root bark has a place in folk medicine; it was used by female slaves in the early U.S. to induce abortion.

Before the age of inkjet and laser printing, the best typing paper was made from cotton fabric. As with fabrics, this pride of place is somewhat less than in previous decades, but cotton still is used in many paper product applications.