Mechanical devices, including tractors and implements, used in farming to save labour. The great variety of farming devices covers a wide range of complexity, from simple hand-held implements used since prehistoric times to the complex harvesters of modern mechanized agriculture. From the early 19th century to the present, the chief source of power in farming has changed from animals to steam power, then to gasoline, and finally to diesel. In developed countries, the number of farmworkers has steadily declined in the 20th century, while farm production has increased because of the use of machinery.
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