Plows
The plow—or plough—one of the oldest types of agricultural implements, is used to break up soil in preparation for planting. Modern plows are also used to bury, or plow under, crop remains at the end of the growing season.
The earliest plow was the swing plow (a plow without wheels) used in Egypt and Mesopotamia by about 4000 b.c. Civilizations that did not have the plow had to do their planting either by broadcasting the seed onto soil without burying it--which wastes a great deal of seed--or by planting seeds one at a time with a stick or sharp piece of antler. The first wheeled plow was developed in what is now Switzerland during the first century b.c. The wheels gave the plow weight and stability and also gave the furrow a more even depth.
The first iron plowshare—the share is the cutting edge of the plow—appeared among the Celts in Britain around 400 b.c. Plows made completely of wood broke easily, especially in rocky soil, and a heavier iron plow was developed in central and northern Europe to accommodate the stiffer soils in those areas. This led to greater food production and eventually a significant population increase around 600 a.d.
Innumerable plow designs were developed in England, the American colonies, and other countries according to the individual farmer's particular needs and resources. Thomas Jefferson is credited with the invention of several plows for use on his Virginia estate.
In 1785 Englishman Robert Ransome patented a plow with a cast-iron share. Later, in 1808, he designed cast-iron plows with detachable pieces, while in 1797 American Charles Newbold invented a single-piece all-iron plow. The problem with Newbold's design was that if any part broke, the whole plow was ruined.
In 1813, Richard B. Chenaworth of Baltimore invented a cast-iron plow with separate share, moldboard, and landside. The landside is the vertical part of the plow that guides it and absorbs the side pressure. The moldboard receives the soil and turns it over. In America, Jethro Wood of Massachusetts invented a plow similar to Chenaworth's. John Lane of Chicago patented a steel plow in 1833, but was unable to recover profits due to patent infringements.
In 1837, American John Deere (1804-1886) developed a steel plow fashioned from a circular saw blade. He was responding to the need of farmers in the midwestern United States whose iron plows could not cut through the difficult prairie soils. Deere began manufacturing the plow the following year, and his company became one of the largest farm machinery manufacturers in the world. His plow played a major role in opening the western states to settlement and agriculture.
The disc plow was first developed in the United States in 1847 but was not actually put to use until 1893. In Australia disc plows were first used in 1877. Similar to a disc harrow, the disc plow more readily cuts through crop stubble and rolls over field obstructions.
Gang plows with twelve to fourteen blades were invented before the American Civil War. They required teams of horses rather than single animals to maintain the necessary momentum for cutting through the soil. American F. S. Davenport invented the sulky plow, which gave the farmer a seat to ride on, in 1864.
A radical change came in 1927 with the introduction of the carried plow. This innovation allowed the plow apparatus to be mounted to the rear of a tractor and carried out to the field, then lowered for plowing. In 1960, the semi-mounted plow was developed to prevent the tractor from tipping. This plow was pulled to the field like a trailer with the gang raised. A rotary plow mixes surface growth with soil, while the chisel plow, has a gang of rigid shanks with shovel points and is used to loosen hard, dry soil prior to regular plowing.
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