Plough
The
plough (American spelling:
plow) is a
tool used in
farming for initial cultivation of soil in preparation for sowing
seed or planting. Ploughs are also used by
industry underseas, for the laying of
cables, as well as preparing the earth for
side-scan sonar in a process used in
oil exploration.
The plough can be regarded as a development of the
pick, or of the
spade. Ploughs were initially pulled by humans, later by
oxen, and later still in some countries, by
horses. Modern ploughs are, in
industrialized countries, powered by
tractors.
Ploughing has several beneficial effects. The major reason for ploughing is to turn over the upper layer of the soil. This may also incorporate the residue from the previous crop into the soil. Ploughing reduces the prevalence of
weeds in the fields, and makes the soil more porous, easing later planting. Excessively deep ploughing or digging brings up
subsoil and mixes subsoil with
topsoil. This can damage the
soil.
The early
German word before sound-shift is
plug and in
Old Prussian plugis. After the German sound shift (p = pf) it became the modern German word
Pflug.
Pre-Industrial Revolution
When agriculture was first developed, simple hand held digging sticks or
hoes would have been used in highly fertile areas, such as the banks of the
Nile where the annual flood rejuvenates the soil, to create furrows wherein seeds could be sown. In order to regularly grow crops in less fertile areas, the soil must be turned to bring nutrients to the surface.
The domestication of
oxen in
Mesopotamia, perhaps as early as the
6th millennium BC, provided mankind with the pulling power necessary to develop the plough. The very earliest ploughs were simple
scratch-ploughs and consisted of a frame holding a vertical wooden stick that was dragged through the topsoil.
These were much later developed into
mouldboard ploughs (American spelling:
moldboard) that turned the soil in one run across the field, depositing the weeds and undecomposed remains of the previous crop under the soil and raising the rain-percolated nutrients back to the surface. This plough also allowed for ploughing while the ground was wet. The water was drained due to channels formed under the overturned earth. Despite a number of innovations, the Romans never achieved the heavy wheeled mouldboard plow, the first linguistic evidence for the heavy wheeled moulded plow appears sometime before or in the 6th century with scattered Slavic groups.
The mouldboard, carried below the frame, is tipped with a
share (also called a
ploughshare), an asymmetric arrow-shaped device designed to slice through the ground horizontally as it moves forward. It also has a
coulter, a sharpened blade or disc, attached to the frame of the plough to cut down through the ground, ahead of the share, and also to cut deepset and tough roots. A runner extending from behind the share to the rear of the plough controls the direction of the plough, because it is held against the bottom land-side corner of the new furrow being formed. The holding force is the weight of the sod, as it is raised and rotated, on the curved surface of the moldboard. Because of this runner, the mouldboard plough is harder to turn around than the scratch plough, and its introduction brought about a change in the shape of fields -- from mostly square fields into longer rectangular "strips" (hence the introduction of the
furlong).
The Girard (or Gerard) plough was developed in the early 14th century in what is now Belgium by Girard de Liege. It was the first plough design to encompass the use of an iron blade.
The first commercially successful
iron plough was the
Rotherham plough, developed by
Joseph Foljambe in
Rotherham,
England, in
1730. It was durable and light, and was engineered after the mathematical principles of
James Small, who designed a mouldboard that would cut, lift and turn over the strip of earth. (All the major components of the Rotherham plough had been well known in China for millennia, and diffusion of technology from China, probably by the Dutch, is highly likely).
Post-Industrial Revolution
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Yaks are used to plow fields in much of Asia. |
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A German farmer (ploughman or plowman) works the land with a horse and plough. |
Steel ploughs were developed during the
Industrial Revolution and were lighter and more durable than ploughs made of iron or wood. The
cast-steel plough was developed by U.S.
blacksmith John Deere in the 1830s. By this time the hitch, to the
draught animals, was adjustable so that the wheel at the front was held onto the ground. The first steel ploughs were
walking ploughs, having two handles held by the ploughman to provide a degree of control over the depth and location of the furrow behind the draughting force. The ploughman often was also controlling the draught animal(s).
Riding ploughs with wheels and a seat for the operator came later, and often had more than one share.
A single draught horse can normally pull a single-furrow plough in clean, light, soil but in heavier soils two animals are needed, one walking on the land and one in the furrow. For ploughs with two or more furrows, one or more horses have to walk on the loose, ploughed, sod -- and that makes hard going for them. It is usual to rest such animals every half hour for about ten minutes.
The
Stump-jump plough is an Australian invention of the 1870s, designed to cope with the breaking up of new farming land, that contains many tree stumps and rocks that would be very expensive to remove from paddocks. The plough uses a moveable weight to hold the ploughshare in position. When a tree stump or other obstruction such as a rock is encountered, the ploughshare is thrown upwards, clear of the obstacle, to avoid breaking the harness or linkage of the whole plough; ploughing can be continued when the weight is returned to the earth after the obstacle is passed.
A simpler system, developed later, uses a concave disk (or a pair of them) set at a large angle to the direction of progress, that uses the concave shape to hold the disk into the soil -- unless something hard strikes the circumference of the disk, causing it to roll up and over the obstruction. As the arrangement is dragged forward, the sharp edge of the disk cuts the soil, and the concave surface of the rotating disk lifts and throws the soil to the side. It doesn't make as good a job as the mouldboard plough (but this is not considered a disadvantage, because it helps fight the wind erosion), but it does lift and break up the soil.
Traditional ploughs can only turn the soil over in one direction, as dictated by the shape of the mouldboard. The resulting method of traversing an entire field leads to the
ridge and furrow effect seen in some ancient fields.
Modern ploughs are reversible, having 2 sets of mouldboards: while one is working the land, the other is carried upside-down in the air. During the cultivation process,
hydraulics are used to turn over the entire implement at each end of the field so that the second set of moulboards can be used. The field can then be traversed in such a way as to keep the land level, avoiding ridges and furrows.
The modern reversible plough is mounted on a
tractor via a
three-point hitch. These commonly have sets of 2 up to 5 mouldboards, but
semi-mounted ploughs, the lifting of which are supplemented by a wheel about half-way along its length, can have as many as 18. The hydraulic system of the tractor is used to lift and reverse the implement, as well as adjust furrow width and depth. The ploughman still has to set the draughting linkage from the tractor so that the plough is carried at the proper angle in the soil. This angle and depth can be controlled automatically by modern tractors.
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A plough in action in South Africa. Notice the soil being turned over. |
The goal for ploughing is to get the soil lose, enrich it with oxygen, get rid of unwanted plants and certain bacteria. The plants that get ploughed in serve as a compost after it has rotten.
One negative effect of plowing is to dramatically increase the rate of
soil erosion, both by wind and water, where soil is moved elsewhere on land or deposited in bodies of water, such as the oceans. Plowing is thought to be a contributing factor to the
Dust Bowl in the US in the 1930's. Alternatives to plowing, such as the
no till method, have the potential to limit damage while still allowing farming.
*Frame
*Frog
*
Share (also called a
plowshare or
ploughshare)
*Mouldboard
*Runner
*Landside
*Shin
*Trashboard
*Handles
*Hitch
*Knife or coulter
On modern ploughs and some older ploughs, the mouldboard is separate from the share and runner, allowing these parts to be replaced without replacing the mouldboard. Abrasion eventually destroys all parts of a plough that contact the soil.
On a vehicle such as a
tram, a
plough is also the name commonly given to the pair of shoes, one pick-up and one return, both attached to a busbar, that draw power from a pair of live rails underneath the road.
*
Aratrum (Ancient Greek plough)
*
Ploughman's lunch*
Snowplow*
Ridge and furrow*
Operation Plowshare*
Plowshares Movement*
Railroad plough*
Kverneland*
Big Dipper, a
constellation also known as
The Plough*
Foot plough*
Breast Ploughs and other antique hand farm tools
