plough
(esp US), plowplow
[plau̇]plow, plough
router plane, plough, plow
Plow
an agricultural implement for primary tillage. The plow is the oldest soil-working implement. It is known from Babylonian and ancient Egyptian depictions, cave drawings in northern Italy and southern Sweden (dating from the second millennium B.C.), and actual finds in peat bogs in Poland. The plow was used in China before the first millennium B.C. All the ancient plows were made of wood and had a shaft for harnessing animals and handles or a split stem for steering. The working part, the share, was held horizontally to form a true plow or obliquely to form a sokha (Russian plow). Plows with an iron share appeared in the first millennium B.C. The Romans invented a forecarriage on wheels, making it possible to regulate the depth of plowing. They used a blade placed in front of the share for cutting through the soil, and boards, which served as mold-boards, attached at an angle to the share for loosening and pushing aside the soil.
In Russia the plow appeared in the forest-steppe zone in the eighth or ninth century A.D., on the eve of the formation of Kievan Rus’. The development of the modern plow dates to the 17th century. The first metal horse-drawn plows appeared at the end of the 18th century. Factory production of such plows in Russia began in 1802, and both those without a forecarriage and those with a Russian forecarriage were produced. The first mechanized plows were produced only after the October Revolution of 1917. The first series-produced tractor plows were manufactured in the USSR by the Odessa October Revolution Plant in 1925. Further development of plow design involved replacing drawn plows with mounted and semimounted ones and changing the cutting width of the plow for more effective use with tractors. In 1973 there were 961,000 general-purpose tractor plows in the USSR. Modern plows are classified according to the type of working parts as share and disk plows; according to the type of motive power as tractor plows (mounted, semimounted, and trailed), horse-drawn, and cable plows; and according to the number of working parts as single-bottom, double-bottom, and multiple plows. Distinctions are also made based on the use— basic, or general-purpose, and special plows—and on the type of plowing—plows for furrowing, inthrow and outthrow plowing, and flat plowing.
In the USSR, the predominant types of plows are the tractor-mounted share plow, the trailed plow, and the semimounted plow. The basic assemblies are the working parts, the mechanism for adjusting plowing depth, the plow clutch, the hydraulic cylinder, the support wheels, and the mounting assembly for mounted plows or hitch for trailed plows. All the assemblies are mounted on a flat or arched beam frame. The working parts of a share plow include the bottom, consisting of a plow head with the share, moldboard, and landside fastened to it; the jointer, which is similar to but smaller than the bottom; and the rolling or knife colter. For deepening the subsoil by 5–12 cm without carrying the soil to the surface, subsoilers are fastened to the plow bottoms. As the plow cuts the surface of the soil, the jointers, located 30–35 cm in front of the bottoms, remove a 10-cm layer of soil and deposit it into a furrow formed by another bottom moving ahead. The bottoms cut with shares and open the soil layer with the field edge of the moldboards. The moldboards lift, crumble, and invert the furrow slices, and cover the soil that the jointers have deposited into the furrow. The rolling colter, located at the rear of the bottom, cuts off the furrow slice, leaving an intact wall and clean furrow. For plowing virgin and fallow lands, the rolling colters are fastened in front of each bottom. The rear portion of the landside presses against the furrow sole, and the side portion presses against the furrow wall and counteracts the pressure exerted by the furrow slice on the plow bottom. Bottoms without moldboards are used to loosen the soil to a depth of 40 cm without inverting the furrow slice.
The wheels used on trailed and semimounted plows not only support the plow assembly but are also fitted with a screw mechanism that allows the plowing depth to be adjusted by raising or lowering the plow on its wheels. Mounted plows also have support wheels with this feature. The plow clutch, used on trailed plows, and the hydraulic cylinder, used on semimounted ones, are used for changing the plow to a transport position. A mounted plow is raised and lowered by the tractor’s hydraulic system.
Disk plows are basically used for plowing up new land after forests have been cleared and for working heavy, packed, weedy, and bog soils. The working parts of these plows are spherical disks that turn on axles mounted on the plow frame.
General-purpose plows are used for the primary plowing of soil to a depth of 20–30 cm. For inthrow and outthrow plowing, plow bottoms that turn the soil to the right are mounted on the plow frames. Flat plowing is done with reversible, pickup, and shuttle plows. The reversible plow has right-handed and left-handed bottoms fastened on the same frame. After each trip of the plow over the ground, the frame is rotated 90° around the longitudinal axis by a turning mechanism. The pickup plow is equipped with sections of right-handed and left-handed bottoms that are operated alternately. The shuttle plow consists of two sections of right-handed and left-handed bottoms that are suspended on the tractor mountings, one in front and the other in back. It works across a slope (along the horizontals) by the shuttle method, and the front and rear sections are used alternately.
Special plows include brush and bog, deep, orchard disk, vineyard, gang, and forest plows and plows for use on rocky soils. The brush and bog plow is used for tilling bog and peat soils, for forest stubbing and clearing after brush has been cut, and for plowing up soils covered with brush and young trees 2–4 m tall. The gang plow is designed for two-and three-depth plowing of alkaline and podzolic soils. With three-depth plowing, the front bottom removes and inverts the upper soil layer and places it in the furrow sole formed by the rear bottom during the previous trip over the ground. The middle bottom lifts the third layer and moves it to the side together with the upper soil layer; it does not invert the layer. At the same time, the rear bottom lifts and inverts the second layer and places it in the furrow sole formed by the middle bottom. With two-depth plowing, the upper layer is either laid on the surface of the field and the middle and lower layers are mixed together or the upper layer is covered to a given depth and the two lower layers are lifted to the surface without being inverted. The deep plow is used for working soil to a depth of 40 cm in vineyards, orchards, and forest stands. The orchard disk plow is used for plowing the soil between the rows in orchards and is equipped with a device that enables it to be shifted to the side. This makes it possible to work the soil beneath mature trees. The forest plow is equipped with a working bottom with right-handed and left-handed moldboards that operate simultaneously. It opens furrows for seeding and planting forest crops in felling areas where the stumps have not been removed, and it has a device for sowing conifer seeds in the furrows. Plows for working rocky soils are equipped with a lever mechanism for lifting the plow bottoms over obstacles in their path.
In the beginning of the 1960’s, Soviet and foreign research institutions and design offices proposed designs for rotary plows and plows with rotary moldboards in order to improve the quality of tillage. The bottom of a plow with a rotary moldboard inverts and loosens the furrow slice at higher operating speeds; it has 30 percent less drag than a share plow. However, the rotary working part does not cover the crop residue sufficiently well, and it mixes the soil layers poorly.
REFERENCES
Sel’skokhoziaistvennaia tekhnika: Katalog, 3rd ed. Moscow, 1967. Karpenko, N. A., and A. A. Zelenev. Sel’skokhoziaistvennye mashiny. Moscow, 1968.Katalog traktorov, sel’skokhoziaistvennykh, zemleroinykh i meliorativ-nykh mashin, transportnykh sredstv, mashin i oborudovaniia dlia me-khanizatsii zhivotnovodcheskikh ferm. Moscow, 1972.
V. KOMARISTOV