Cotton (Gossypium barbadense) grows especially well and matures early in sandy loam soils or loamy sand soils. Although it's typically thought of as a crop that's grown commercially, home gardeners can cultivate cotton too. Cotton will grow in U.S. Department of Agriculture plant hardiness zones 9a through 11.
The Best Soil for Cotton
The cotton favorite, sandy loam, is silt and clay that contains some sand. Loamy sand contains some silt and clay. In addition to those soils, cotton fares well in soil that's gray on top with yellow clay underneath. It also likes soil that's gray on top with yellowish-red sandy clay beneath the surface. While cotton likes sandy soils, these are subject to erosion by rains and high winds. Farmers in Alabama have addressed this by planting rye as a cover crop. Mature rye has roots that hold the sandy soil in place. After it matures, farmers flatten the rye a month before planting cotton.
Cotton and Soil Fertility
For years, it was commonly thought that cotton decreased soil fertility. In fact, farmers knew that cotton was tolerant of infertile soil so they planted it on the poorest soil and used its seed for fertilizer. They continued this practice for decades, further debilitating the quality of the already poor soil. This led many to conclude that cotton was hard on soil. It is not -- any soil will deteriorate if the same crop is planted on it year after year. You can grow cotton in poor garden soil, but vary what you plant from time to time.
Poor Soil for Cotton
Cotton planted in heavy clay soil risks infestation by boll weevils. Cotton does not grow well on soil that's red or brownish-yellow on the surface with red clay underneath. High concentrations of salt in the top 4 inches of soil can cause it to crust, leading to poor growth of cotton seedlings. While cotton is typically planted from 1/2 to 1 1/2 inch deep, planting should be at the shallow end of this range on sandy coastal soil that tends to crust from high salt content.
Soil Temperature an pH
For the best cottonseed germination, the soil should have an average soil temperature of 86 degrees Fahrenheit at a depth of 8 inches. Cotton grows best on sandy soils with a minimum 5.5 soil pH and on clay soils with a minimum 5.8 soil pH. Soils should be well drained.