The Cotton Crop

Cotton is grown in the hotter regions of approximately 65 tropical/subtropical and temperate countries around the world. Whereas cotton is intrinsically a hot weather crop and performs optimally in the tropics and subtropics, varieties have been developed that perform well and are well adapted to the warmer temperate areas of cotton-growing countries. Cotton is grown on many soil types, ranging from sandy to clays but prefers a heavy loam. Cotton is one of the most efficient crops in terms of water utilization in that it produces one of the highest quantities of dry matter per liter of water. Duration from planting to harvest ranges from 140 to 250 days (Hearn and Fitt 1992); it is possible to grow cotton in regions where the frost-free period is less than 180 days. The timing of planting and harvesting of cotton operations differ in the Northern and Southern Hemisphere and are listed below for some of the major cotton-growing countries. Brazil is divided into two regions in terms of cotton production. In southern Brazil there is a high input intensive cotton production system and in the north a low input system featuring perennial cotton.

Water requirements for cotton are critical – ideally it prefers an early wet period to promote vegetative growth followed by a dry season during which the flowers and fruits mature and dry. Irrigation is often used to optimize availability of water. Cotton requires abundant sunshine and an optimal average growing temperature in the range of 25oC to 30oC. Cotton production can be labor or capital intensive, with the former normally applying to developing countries where labor cost is low and capital limited, whereas the reverse is normally the case for industrial countries.

Cotton is a member of the genus Gossypium and belongs to the Malvaceae family which also includes the flowering shrub Hibiscus and Okra. More than 95 % of commercial cotton is upland cotton, Gossypium hirsutum, while long staple cotton, G. barbadense, occupies a small area of <5%. Both cultivated cotton species are self pollinating allotetraploids, are incompatible with the diploid wild species of cotton, and there are no identified non-cotton wild relatives with which upland and long staple cotton will outcross. Two species of Asiatic cotton, G. arboretum and G. herbaceum are grown in restricted areas of Asia and Africa; these are diploid and incompatible with upland and long staple cotton.

Upland cotton and long staple cotton are both perennial dicots, but they are normally cultivated as an annual crop. With few exceptions, the commercial seeds that are sold globally to farmers are varieties rather than hybrids: India is an exception where approximately 50% of cotton is hybrid.

Cotton is grown principally for the fiber although a small quantity of the seed is used as a source of food, feed and oil for humans and animals. Cotton seed oil is refined before it is used for human consumption to remove Gossypol which is toxic to humans and monogastric animals. The fruit of the cotton plant is more familiarly known as the boll, which contains approximately ten cotton seeds that are surrounded by the fibers (lint) which grow from the coats of the seed. The cotton lint is the primary commercial product that generates income for cotton producers and lint yield is approximately one-third by weight of seed cotton which is the product harvested by farmers. The lint is separated from the seed during processing at a ginnery. Given that cotton is self pollinating, farmers can save seeds for planting. However, subsequent to the ginning process there are small fibers (linters) still attached to the seed which require further processing (delinting) before they can be used as high quality seed for optimal production of cotton, so in practice it pays farmers to buy new seed annually. World production of lint has more than doubled from 9.8 million tons in 1960/61 to 21.2 million tons in 2001/02. Lint yield has also more than doubled from 305 kg/hectare to 635 kg/hectare over the last 20 years while the area of cotton has remained approximately the same. Yields in Latin America and Africa have improved fairly slowly during the last 20 years whereas significant gains have been made in selected countries such as China in Asia.

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Related topics:

• Global distribution of cotton in developing and industrial countries, by area, production, consumption, imports, and exports
• Number of cotton farmers worldwide and size of farms
• Insect pests of cotton
• Crop losses due to insect pests of cotton and the cost of control
• Global insecticide usage on cotton
• The use of Bt genes in cotton
• Assessment of environmental risk and Insect Resistance Management (IRM) strategies
• Global adoption of Bt cotton
• Bt cotton experience to date
• Summary: Agronomic, Environmental, Social and Economic Benefits
• Future global potential for Bt cotton: opportunities and challenges
• Highlights

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