In many societies, slave labor was utilized to pick the cotton, increasing the plantation owner's profit margins (See
Atlantic slave trade). The first practical cotton picker was invented over a period of years beginning in the late 1920s by John Daniel Rust (1892–1954) with the later help of his brother Mack Rust. Other inventors had tried designs with a barbed spindle to twist cotton fibers onto the spindle and then pull the cotton from the boll, but these early designs were impractical because the spindle became clogged with cotton. Rust determined that a smooth, moist spindle could be used to strip the fibers from the boll without trapping them in the machinery. In 1933 John Rust received his first
patent, and eventually, he and his brother owned forty-seven patents on cotton picking machinery. However, during the
Great Depression it was difficult to obtain financing to develop their inventions. ) In 1935 the Rust brothers founded the Rust Cotton Picker Company in
Memphis, Tennessee, and on 31 August 1936 demonstrated the Rust picker at the Delta Experiment Station in
Stoneville, Mississippi. Although the first Rust picker was not without serious deficiencies, it did pick cotton and the demonstration attracted considerable national press coverage. Nevertheless, the Rusts' company did not have the capability of manufacturing cotton pickers in significant quantities. With the success of the Rust picker, other companies redoubled their efforts to produce practical pickers not based on the Rust patents. Then, widespread adoption was delayed by the manufacturing demands of
World War II. The
International Harvester Company produced a commercially successful commercial cotton picker in 1944. After World War II, the
Allis-Chalmers Manufacturing Company manufactured cotton pickers using an improved Rust design. In the following years mechanical pickers were gradually improved and were increasingly adopted by farmers.
Cotton plant improvements To make mechanical cotton pickers more practical, improvements in the cotton plant and in cotton culture were also necessary. In earlier times, cotton fields had to be picked by hand three and four times each harvest season because the bolls matured at different rates. It was not practical to delay picking until all the bolls were ready for picking because the quality of the cotton deteriorated as soon as bolls opened. But about the time mechanical pickers were introduced, plant breeders developed hybrid cotton varieties with bolls higher off the ground and that ripened uniformly. With those innovations, the harvester could make just one pass through the field. Also, herbicides were developed to defoliate the plants and drop their leaves before the picker came through, producing a cleaner harvest. == Conventional harvester ==