tractor

In agriculture, a powerful motor vehicle, commonly having large rear wheels or caterpillar tracks, used for pulling farm machinery and loads. It is usually powered by a diesel engine and has a power-takeoff mechanism for driving machinery, and a hydraulic lift for raising and lowering implements.

The average weight of tractors in developed countries has tripled over the period 1970–1998. This increase in size is actually detrimental to crop yield as compacted soil is less fertile.

Japanese researchers have developed (1998) a tractor that tills, seeds, and fertilizes fields without needing a driver. It uses global positioning satellites to navigate and has an error margin of less than 10 cm/4 in.