plough

 

or plough, agricultural implement used to cut furrows in and turn up the soil, preparing it for planting. The plow is generally considered the most important tillage tool. Its beginnings in the Bronze Age were associated with the domestication of draft animals and the increasing demand for food resulting from the rise of cities. The plow is depicted on Egyptian monuments, mentioned in the Old Testament, and described by Hesiod and Vergil. The early plow consisted simply of a wooden wedge, tipped with iron and fastened to a single handle, and a beam, which was pulled by men or oxen. Such implements were capable of breaking but not of inverting the soil. The plow evolved gradually until c.1600, when British landlords attempted greater improvements. The first half of the 18th cent. saw the introduction into England of the moldboard, a curved board that turns over the slice of earth cut by the share. Important improvements in design and materials were made in the early part of the 19th cent. They included streamlined moldboards, replaceable shares, and steel plows with self-scouring moldboards. Standardized by 1870, the modern moldboard plow has been improved by various attachments, e.g., the colter, a sharp blade or disk that cuts the ground in advance of the share. In 19th-century America horses largely replaced oxen for drawing plows. Tractors now supply this power in most developed parts of the world. With more powerful tractors, larger plows have come into use. Among the various types of plows in use today are the reversible two-way plow for contour plowing; listers and middlebusters, which prepare shallow beds; the disk plow, whose revolving concave disks are useful in working hard or dry soil; the rotary plow, with an assembly of knives on the shaft that mix the surface growth with the soil; and the chisel plow, with points mounted on long shanks to loosen hard, dry soils and shatter subsurface hardpan. The plow often symbolizes agriculture, as in the great seals of New Jersey, Pennsylvania, Tennessee, and other states.

Bibliography

See publications of the U.S. Dept. of Agriculture; C. Culpin, Farm Machinery (12th ed. 1992).

The plough (American spelling: plow) is a tool used in farming for initial cultivation of soil in preparation for sowing seed or planting. It has been a basic instrument for most of recorded history, and represents one of the major advances in agriculture. The primary purpose of ploughing is to turn over the upper layer of the soil, bringing fresh nutrients to the surface, while burying weeds and the remains of previous crops, allowing them to break down. It also aerates the soil, and allows it to better hold moisture. In modern use, a ploughed field is typically left to dry out, and is then harrowed before planting.

Ploughs were initially pulled by humans, later by oxen, and later still in some countries, by horses. In industrialized countries, the first mechanical means of pulling a plough used steam-power (ploughing engines or steam tractors), but these were gradually superseded by internal-combustion-powered tractors. Until the past two decades it was routinely used even on previously tilled land, in the Midwest of the United States and elsewhere. Awareness of the potential for soil damage has led to reduced use in favour of shallower ploughing and other less invasive tillage techniques. Ploughs are still 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 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.

History of the plough

Hoeing

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.

Scratch plough

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, or ard, which consisted of a frame holding a vertical wooden stick that was dragged through the topsoil. This turns over a strip of land directly over the ploughed path, which can then be planted. Because this form of plough leaves a strip of undisturbed earth between the rows, according to Lynn White, "cross-ploughing is necessary, with the result that, in regions where the scratch-plough is used, fields tend to be squarish in shape, roughly as wide as they are long."^[1] In the archeology of northern Europe, these squarish fields are referred to as "Celtic fields".

The French historian Marc Bloch, whose pioneering work contributed to our distinction between the scratch and mouldboard ploughs,^[2] emphasizes the difference between the two on the basis of having wheels. His research in medieval French agricultural history showed the existence of names for two different ploughs, "the araire was wheel-less and had to be dragged across the fields, while the charrue was mounted on wheels".^[3]

Crooked ploughs

The Greeks apparently introduced the next major advance in plough design; the crooked plough, which angled the cutting surface forward, leading to the name. The cutting surface was often faced with iron. Iron was an expensive metal, so in times of war it was melted down to make weapons. This is the origin of the term "weapons to ploughshares", a turn of phrase on this ancient practice.

Mouldboard plough

A major advance in plough design was the mouldboard plough (American spelling: moldboard), which supplanted the cutting blade, the coulter, with a wedge-shaped surface, the mouldboard. When dragged through a field, a slice of the topsoil on either side of the cut was lifted up and flipped over by the mouldboard, falling beside the plough. This not only opened up the area directly below the mouldboard, but also covered the area beside it, thereby turning over a much wider strip in one pass, the classic furrow. This greatly reduced the amount of time needed to prepare a field, and as a consequence, allowed a farmer to work a larger area of land. In addition, the resulting pattern of low (under the mouldboard) and high (beside it) ridges in the soil formed water channels, allowing the soil to drain. In areas where snow buildup is an issue, this allows the soil to be planted earlier as the snow runoff is drained away more quickly.

Parts of a mouldboard plough:- There are 5 major parts of a mouldboard plough-1.Mouldboard 2.Share 3.Landside 4.Frog 5.Tailpiece

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 mouldboard. 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).

An advance on the basic design was the ploughshare, a horizontal cutting surface mounted on the tip of the mouldboard introduced by the Celts in Britain around 4000 BC. Early mouldboards were basically wedges that sat inside the cut formed by the coulter, turning over the soil just on either side. The ploughshare spread the cut horizontally below the surface, so when the mouldboard lifted it, a wider area of soil was turned over.

Heavy ploughs

In the basic mouldboard plough the depth of the cut is adjusted by lifting against the runner in the furrow, which limited the weight of the plough to what the ploughman could easily lift. This limited the construction to a small amount of wood, and metal edges is possible. These ploughs were fairly fragile, and were unsuitable for breaking up the heavier soils of northern Europe. The introduction of wheels to replace the runner allowed the weight of the plough to increase, and in turn allowed the use of a much larger mouldboard that was faced by metal. These heavy ploughs led to greater food production and eventually a significant population increase around 600 a.d.

Despite a number of innovations, the Romans never achieved the heavy wheeled mouldboard plough; Lynn White dates its first indisputable appearance after the Roman period to 643, in a northern Italian document.^[4] On the other hand, White describes the linguistic researches of B. Bratanič of the University of Zagreb, who showed that twenty-six technical terms connected with the heavy plough and its use "are to be found in all three of the great Slavic lingusistic groups, the eastern, western and southern", pointing to its adoption by these people before their division in the later sixth century, and indicating that the mouldboard plough was invented by 600 then introduced to Europe. Despite this, "Bratanič does not claim the invention of the heavy plough for the Slavs, but for 'some northern peasant culture' as yet unidentified."^[5] It appears to have been independently developed in Han Dynasty China, around 100 BC. Despite the date or place of its origins, White argues that adoption of the mouldboard plough, accompanied with adoption of the three-field system, occurred in the later eighth and early ninth centuries, and led to an improvement of the agricultural productivity per unit of land in northern Europe.^[6]

Improved designs

The basic plough with coulter, ploughshare and mouldboard remained in use for a millennia. Major changes in design did not become common until the Age of Enlightenment, when there was rapid progress in design. The Dutch are credited with the introduction of newer shapes for the mouldboard in the 1600s, although these shapes were known earlier in China and may have been discovered by the Dutch while there.^[7]

Joseph Foljambe in Rotherham, England, in 1730 used these new shapes as the basis for the Rotherham plough, which also covered the mouldboard with iron.^[8] Unlike the heavy plough, the Rotherham (or Rotherham swing) plough consisted entirely of the coulter, mouldboard and handles. It was much lighter than conventional designs and became very popular in England. It may be the first plough to be widely built in factories.

James Small further improved the design. Using mathematical methods he experimented with various designs until he arrived at a shape cast from a single piece of iron, the Scots Plough. This was again improved on by Jethro Wood, a blacksmith of Scipio, New York, who made a three-part Scots Plough that allowed a broken piece to be replaced. John Deere introduced the first steel plough; it was so much stronger than iron designs that it was able to work the soil in areas of the US that had earlier been considered unsuitable for farming. Improvements on this followed developments in metallurgy; steel coulters and shares with softer iron mouldboards to prevent breakage, the "chilled plough" which is an early example of face hardened steel,^[9] and eventually the face of the mouldboard grew strong enough to dispense with the coulter.

Post-Industrial Revolution

Early steel ploughs, like those for thousands of years prior, were "walking ploughs", directed by the ploughman holding onto handles on either side of the plough. The steel ploughs were so much easier to draw through the soil that the constant adjustments of the blade to react to roots or clods was no longer necessary, as the plough could easily cut through them. It was not long after that the first "riding ploughs" appeared. On these, wheels kept the plough at an adjustable level above the ground, while the ploughman sat on a seat where he would have earlier walked. Direction was now controlled mostly through the draught team, with the handles allowing fine adjustments. This led very quickly to riding ploughs with multiple mouldboards, dramatically increasing ploughing performance.

A single draught horse can normally pull a single-furrow plough in clean light soil, but in heavier soils two horses 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, and treads the newly ploughed land down. It is usual to rest such horses every half hour for about ten minutes.

Amish farmers tend to use a team of about seven horses or mules when spring ploughing and as Amish farmers often help each other plough, teams are sometimes changed at noon. Using this method about 10 acres can be ploughed per day in light soils and about 2 acres in heavy soils.

In the Appalachian region, ploughs are still used on some rural farms. It is not uncommon to see very steep land, not tillable by mechanical means due to the threat of causing the vehicle to roll, being ploughed with one horse or mule and a "hillside plough". The hillside plough has the advantage of being easily and quickly switched from turning the soil to the left, to turning the soil to the right, and back and forth. When the farmer gets to the end of the row and the draught animal has completed the turn back to plough the next row, the plough is lifted just enough to clear the soil, a manual lever is depressed, and the plough blade itself can be swung back under the plough where it clicks into place into the opposite configuration. This saves the animal's strength by allowing the plough to always turn the soil downhill, which makes for easier pulling. The hillside plough is only good for use on steep hillsides with easily tillable soil, due to its light weight, which allows the farmer to do the lift and switch procedure at the end of each row.

Steam ploughing

The advent of the mobile steam engine allowed steam power to be applied to ploughing from about 1850. In Europe, soil conditions were too soft to support the weight of the heavy traction engines. Instead, counterbalanced wheeled ploughs, known as balance ploughs, were drawn by cables across the fields by pairs of ploughing engines.

In America the firm soil of the Plains allowed direct pulling with steam tractors, such as the big Case, Reeves or Sawyer Massey breaking engines. Gang ploughs of up to fourteen bottoms were used. Often these big ploughs were used in regiments of engines, so that in a single field there might be ten steam tractors each drawing a plough. In this way hundreds of acres could be turned over in a day. Only steam engines had the power to draw the big units. When gas engines appeared, they had neither the strength nor the ruggedness compared to the big steam tractors. Only by reducing the number of shares could the work be completed.

Stump-jump ploughs

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 plough's harness or linkage; 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.

Reversible plough

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 whole plough 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 7 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. The goal for ploughing is to loosen the soil, enrich it with oxygen, get rid of unwanted plants and certain bacteria. The plants that get ploughed under decompose, and serve as compost.

Chisel plough

The chisel plough is a common tool to get deep tillage with limited soil disruption. The main function of this plough is to loosen and aerate the soils while leaving crop residue at the top of the soil. This plough can be used to reduce the effects of compaction and to help break up plowpan and hardpan. Unlike many other ploughs the chisel will not invert or turn the soil. This characteristic has made it a useful addition to no-till and limited-tillage farming practices which attempt to maximize the erosion prevention benefits of keeping organic matter and farming residues present on the soil surface through the year. Because of these attributes, the use of a chisel plough is considered by some to be more sustainable than other types of plough, such as the Mouldboard Plough.

The chisel plough is typically set to run up to a depth of eight to twelve inches (200 to 300 mm). However some models may run much deeper. Each of the individual ploughs, or shanks, are typically set from nine inches to twelve inches apart. Such a plough can encounter significant soil drag, consequently a tractor of sufficient power and good traction is required. When planning to plough with a chisel plough it is important to bear in mind that 10 to 15 horsepower (7 to 11 kW) per shank will be required.

Use of the mouldboard plough

In modern use, the mouldboard plough was used for three reasons:-

• Foremost was the control of weeds. In this function, mouldboard ploughing is very successful, a farmer can control weed growth with far fewer herbicides by using this technique than is otherwise possible with any other method, aside from hand weeding, which is labour-intensive and not practical for large operations.
• To break up the soil for planting.
• To warm the soil for planting.

Only the first reason for mouldboard ploughing really paid off. Most plants require little soil agitation to germinate, so breaking up soil is unnecessary beyond what a planting implement accomplishes on its own. Soil warming is also unnecessary beyond two or three inches below the surface, therefore bringing black fresh soil which heats more quickly and more deeply after the final frost of the year is unneeded.

Problems with mouldboard ploughing

Mouldboard ploughing has become increasingly recognized as a highly destructive farming practice with the possibility of rapidly depleting soil resources. In the short term, however, it can be successful, hence the reason it was practised for such a long time. A field that is mouldboarded once will generally have an extraordinary one time yield as the larvae of pests and seed from weeds are buried too deeply to survive. After the first harvest, however, continued mouldboarding will diminish yields greatly.

The diminishing returns of mouldboard ploughing can be attributed to a number of side effects of the practice:-

• Foremost is the formation of hardpan, or the calcification of the sub layer of soil. In some areas, hardpan could once be found so thick it could not be broken up with a pickaxe. The only effective means of removing hardpan is using a "ripper", or chisel plough, which is pulled through the hardpan by an extremely powerful and costly tractor. Obviously, this layer eventually becomes impenetrable to the roots of plants and restricts growth and yields. This layer also becomes impenetrable to water, leading to flooding and the drowning of crops.
• Mouldboard ploughing rapidly depletes the organic matter content of soil and promotes erosion; these two problems go hand in hand. As soil is brought to the surface, the root structure of the previous harvest is broken up, and the natural adhesion of soil particles is also lost; though loose soil appears good for plant germination (and it is), this loose soil without cohesion is highly susceptible to erosion, multiplying the rate of erosion by several factors compared to a non-mouldboarded plot. This increased rate of erosion will not only outpace the rate of soil genesis but also the replacement rate for organics in the soil, thus depleting the soil more rapidly than normal.
• Mouldboard ploughing leads to increased soil compaction and loss of pore space within the soil. Soil is a bit like a bucket full of balls filled with sand. Each ball represents a cohesive particle of soil, and when stacked the balls leave a great deal of air space, required for healthy root growth and proper drainage. Mouldboarding so disturbs the soil that it breaks these balls and releases their contents. When this happens, the much smaller particles that are within the larger particles are released and pore space diminishes, leading to hard compacted soil that floods easily and restricts root growth.

Soil erosion

One negative effect of ploughing 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. Ploughing is thought to be a contributing factor to the Dust Bowl in the US in the 1930s. Alternatives to ploughing, such as the no till method, have the potential to limit damage while still allowing farming.

Plough parts

• 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.

See also

• Ard (plough) (Prehistoric plough)
• Aratrum (Ancient Greek plough)
• Sokha (Old Russian scratch-plough)
• Snowplow
• Ridge and furrow
• Railroad plough
• Foot plough
• Museum of Scottish Country Life

Notes

References

• The Genius of China", Robert Temple, Prion Books Limited, ISBN 1853752924

External links

• The Rotherham Plough – the first comercially successful iron plough
• History of the steel plough – as developed by John Deere in the US
• Breast Ploughs and other antique hand farm toolsnrm:Tchéthue

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