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Published online by Cambridge University Press: 28 April 2015
Farming practices in the United States have been shifting from labor intensive to relatively more capital intensive methods with simultaneous development of larger implements and more powerful tractors. In 1956, the largest general purpose farm tractor available was about 57 horsepower, but by 1969 several tractors in excess of 130 horsepower were available. Estimates by the United States Department of Agriculture indicate that by 1970 the average tractor sold will be about 80 horsepower compared with approximately 68 horsepower in 1967.