<P> Cotton remained a key crop in the Southern economy after emancipation and the end of the Civil War in 1865 . Across the South, sharecropping evolved, in which landless black and white farmers worked land owned by others in return for a share of the profits . Some farmers rented the land and bore the production costs themselves . Until mechanical cotton pickers were developed, cotton farmers needed additional labor to hand - pick cotton . Picking cotton was a source of income for families across the South . Rural and small town school systems had split vacations so children could work in the fields during "cotton - picking ." </P> <P> It was not until the 1950s that reliable harvesting machinery was introduced (prior to this, cotton - harvesting machinery had been too clumsy to pick cotton without shredding the fibers). During the first half of the 20th century, employment in the cotton industry fell, as machines began to replace laborers and the South's rural labor force dwindled during the World Wars . </P> <P> Cotton remains a major export of the southern United States, and a majority of the world's annual cotton crop is of the long - staple American variety . </P> <P> Successful cultivation of cotton requires a long frost - free period, plenty of sunshine, and a moderate rainfall, usually from 60 to 120 cm (24 to 47 in). Soils usually need to be fairly heavy, although the level of nutrients does not need to be exceptional . In general, these conditions are met within the seasonally dry tropics and subtropics in the Northern and Southern hemispheres, but a large proportion of the cotton grown today is cultivated in areas with less rainfall that obtain the water from irrigation . Production of the crop for a given year usually starts soon after harvesting the preceding autumn . Cotton is naturally a perennial but is grown as an annual to help control pests . Planting time in spring in the Northern hemisphere varies from the beginning of February to the beginning of June . The area of the United States known as the South Plains is the largest contiguous cotton - growing region in the world . While dryland (non-irrigated) cotton is successfully grown in this region, consistent yields are only produced with heavy reliance on irrigation water drawn from the Ogallala Aquifer . Since cotton is somewhat salt and drought tolerant, this makes it an attractive crop for arid and semiarid regions . As water resources get tighter around the world, economies that rely on it face difficulties and conflict, as well as potential environmental problems . For example, improper cropping and irrigation practices have led to desertification in areas of Uzbekistan, where cotton is a major export . In the days of the Soviet Union, the Aral Sea was tapped for agricultural irrigation, largely of cotton, and now salination is widespread . </P>

Who produces the most cotton in the us