Hoeing When
agriculture was first developed, soil was turned using simple hand-held
digging sticks and
hoes. A terracotta model of the early ards was found at
Banawali, India, giving insight into the form of the tool used. The ard remained easy to replace if it became damaged and easy to replicate. The earliest was the bow ard, which consists of a draft-pole (or beam) pierced by a thinner vertical pointed stick called the head (or body), with one end being the stilt (handle) and the other a share (cutting blade) dragged through the topsoil to cut a shallow furrow suitable for most cereal crops. The ard does not clear new land well, so hoes or mattocks had to be used to pull up grass and undergrowth, and a hand-held,
coulter-like ristle could be made to cut deeper furrows ahead of the share. Because the ard left a strip of undisturbed earth between furrows, the fields were often cross-ploughed lengthwise and breadth-wise, which tended to form squarish
Celtic fields. The heavy soils of Northern Europe were difficult to work with a scratch plough. A coulter (or skeith) could be added to cut vertically into the ground just ahead of the share (in front of the frog), a wedge-shaped cutting edge at the bottom front of the mould board with the landside of the frame supporting the under-share (below-ground component). The heavy iron moldboard plough was invented in
China's
Han Empire in the 1st and 2nd century, and from there it spread to the
Netherlands, which led the Agricultural Revolution. The mould-board plough introduced in the 18th century was a major advance in technology. When dragged through a field, the coulter cuts down into the soil and the share cuts horizontally from the previous furrow to the vertical cut. This releases a rectangular strip of sod to be lifted by the share and carried by the mould board up and over, so that the strip of
sod (slice of the
topsoil) that is being cut lifts and rolls over as the plough moves forward, dropping back upside down into the furrow and onto the turned soil from the previous run down the field. Each gap in the ground where the soil has been lifted and moved across (usually to the right) is called a furrow. The sod lifted from it rests at an angle of about 45 degrees in the adjacent furrow, up the back of the sod from the previous run. A series of ploughings run down a field leaves a row of sods partly in the furrows and partly on the ground lifted earlier. Visually, across the rows, there is the land on the left, a furrow (half the width of the removed strip of soil) and the removed strip almost upside-down lying on about half of the previous strip of inverted soil, and so on across the field. Each layer of soil and the gutter it came from forms a classic furrow. The mould-board plough greatly reduced the time needed to prepare a field and so allowed a farmer to work a larger area of land. In addition, the resulting pattern of low (under the mould board) and high (beside it) ridges in the soil forms water channels, allowing the soil to drain. In areas where snow build-up causes difficulties, this lets farmers plant the soil earlier, as the
meltwater run-off drains away more quickly.
Parts There are five major parts of a mouldboard plough: • Mouldboard • Share • Landside (short or long) • Frog (sometimes called a standard) • Tailpiece The
share, landside and mould board are bolted to the frog, which is an irregular piece of cast iron at the base of the plough body, to which the soil-wearing parts are bolted. The share is the edge that makes the horizontal cut to separate the furrow slice from the soil below. Conventional shares are shaped to penetrate soil efficiently: the tip is pointed downward to pull the share into the ground to a regular depth. The clearance, usually referred to as suction or down suction, varies with different makes and types of plough. Share configuration is related to soil type, particularly in the down suction or concavity of its lower surface. Generally three degrees of clearance or down suction are recognised: regular for light soil, deep for ordinary dry soil, and double-deep for clay and gravelly soils. As the share wears away, it becomes blunt and the plough will require more power to pull it through the soil. A plough body with a worn share will not have enough "suck" to ensure it delves the ground to its full working depth. -drawn ploughs used for rice-farming (1873) In addition, the share has horizontal suction related to the amount its point is bent out of line with the land side. Down suction causes the plough to penetrate to proper depth when pulled forward, while horizontal suction causes the plough to create the desired width of furrow. The share is a plane part with a trapezoidal shape. It cuts the soil horizontally and lifts it. Common types are regular, winged-plane, bar-point, and share with mounted or welded point. The regular share conserves a good cut but is recommended on stone-free soils. The winged-plane share is used on heavy soil with a moderate amount of stones. The bar-point share can be used in extreme conditions (hard and stony soils). The share with a mounted point is somewhere between the last two types. Makers have designed shares of various shapes (trapesium, diamond, etc.) with bolted point and wings, often separately renewable. Sometimes the share-cutting edge is placed well in advance of the mould board to reduce the pulverizing action of the soil. The
mould board is the part of the plough that receives the furrow slice from the share. • The general-purpose mould board has a low draft body with a gentle, cross-sectional convex curve from top to bottom, which turns a furrow three parts wide by two parts deep, e. g. wide by deep. It turns the furrow slice slowly almost without breaking it, and is normally used for shallow ploughing (maximum depth). It is useful for grassland ploughing and sets up the land for weathering by winter frosts, which reduces the time taken to prepare a seedbed for spring sown crops. • The digger mould board is short, abruptly curved with a concave cross-section both from top to bottom and from shin to tail. It turns the furrow slice rapidly, giving maximum shatter, deeper than its width. It is normally used for very deep ploughing ( deep or more). It has a higher power requirement and leaves a very broken surface. Digger ploughs are mainly used for land for potatoes and other root crops. • The semi-digger mould board is somewhat shorter than the general-purpose mould board, but with a concave cross-section and a more abrupt curve. Being intermediate between the two mould boards described above, it has a performance that comes in between (approximately deep), with less shattering than the digger mouldboard. It turns an almost square-sectioned furrow and leaves a more broken surface finish. Semi-digger mould boards can be used at various depths and speeds, which suits them for most of the general ploughing on a farm. • In addition, slatted mould boards are preferred by some farmers, though they are a less common type. They consist of a number of curved steel slats bolted to the frog along the length of the mould board, with gaps between the slats. They tend to break up the soil more than a full mould board and improve soil movement across the mould board when working in sticky soils where a solid mould board does not scour well. The
land side is the flat plate which presses against and transmits the lateral thrust of the plough bottom to the furrow wall. It helps to resist the side pressure exerted by the furrow slice on the mould board. It also helps to stabilise the plough while in operation. The rear bottom end of the landslide, which rubs against the furrow sole, is known as the heel. A heel iron is bolted to the end of the rear of the land side and helps to support the back of the plough. The land side and share are arranged to give a "lead" towards the unploughed land, so helping to sustain the correct furrow width. The land side is usually made of solid medium-carbon steel and is very short, except at the rear bottom of the plough. The heel or rear end of the rear land side may be subject to excessive wear if the rear wheel is out of adjustment, and so a chilled iron heel piece is frequently used. This is inexpensive and can be easily replaced. The land side is fastened to the frog by plough bolts. The
frog (standard) is the central part of the plough bottom to which the other components of the bottom are attached. It is an irregular piece of metal, which may be made of cast iron for cast iron ploughs or welded steel for steel ploughs. The frog is the foundation of the plough bottom. It takes the shock resulting from hitting rocks, and therefore should be tough and strong. The frog is in turn fastened to the plough frame. 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 mould board. Because of this runner, the mould board plough is harder to turn around than the scratch plough, and its introduction brought about a change in the shape of fieldsfrom mostly square fields into longer rectangular "strips" (hence the introduction of the
furlong).
Iron ploughshare An advance on the basic design was the iron ploughshare, a replaceable horizontal cutting surface mounted on the tip of the share. The earliest ploughs with a detachable and replaceable share date from around 1000 BC in the
Ancient Near East, and the earliest iron ploughshares from about 500 BC in China. Early mould boards were wedges that sat inside the cut formed by the coulter, turning over the soil to the side. The ploughshare spread the cut horizontally below the surface, so that when the mould board lifted it, a wider area of soil was turned over. Mould boards are known in Britain from the late 6th century onwards.
Types There are multiple types of ploughs available. • Mould board ploughs cut the soil into pieces. • Disc ploughs can be used where mould ploughs are not suitable. • Rotary ploughs are used to prepare seed beds.
Plough wheel • The gauge wheel is an auxiliary wheel to maintain uniform depths of ploughing in various soil conditions. It is usually placed in a hanging position. • The land wheel of the plough runs on the ploughed land. The spring release was used in the past almost universally on trailing-type ploughs with one to three or four bottoms. It is not practical on larger ploughs. When an obstruction is encountered, the spring release mechanism in the hitch permits the plough to uncouple from the tractor. When a hydraulic lift is used on the plough, the hydraulic hoses will also usually uncouple automatically when the plough uncouples. Most plough makers offer an automatic reset system for tough conditions or rocky soils. The re-set mechanism allows each body to move rearward and upward to pass without damage over obstacles such as rocks hidden below soil surface. A heavy leaf or coil-spring mechanism that holds the body in its working position under normal conditions resets the plough after the obstruction is passed. Another type of auto-reset mechanism uses an oil (hydraulic) and gas accumulator. Shock loads cause the oil to compress the gas. When the gas expands again, the leg returns to its working ploughing position after passing over the obstacle. The simplest mechanism is a breaking (shear) bolt that needs replacement. Shear bolts that break when a plough body hits an obstruction are a cheaper overload protection device. Trip-beam ploughs are constructed with a hinge point in the beam. This is usually located some distance above the top of the plough bottom. The bottom is held in normal ploughing position by a spring-operated latch. When an obstruction is encountered, the entire bottom is released and hinges back and up to pass over the obstruction. It is necessary to back up the tractor and plough to reset the bottom. This construction is used to protect the individual bottoms. The automatic reset design has only recently been introduced on US ploughs, but has been used extensively on European and Australian ploughs. Here the beam is hinged at a point almost above the point of the share. The bottom is held in the normal position by a set of springs or a hydraulic cylinder on each bottom. When an obstruction is encountered, the plough bottom hinges back and up in such a way as to pass over the obstruction, without stopping the tractor and plough. The bottom automatically returns to normal ploughing position as soon as the obstruction is passed, without any interruption of forward motion. The automatic reset design permits higher field efficiencies since stopping for stones is practically eliminated. It also reduces costs for broken shares, beams and other parts. The fast resetting action helps produce a better job of ploughing, as large areas of unploughed land are not left, as they are when lifting a plough over a stone.
Loy ploughing Manual loy ploughing was a form used on small farms in Ireland where farmers could not afford more, or on hilly ground that precluded horses. It was used up until the 1960s in poorer land. It suited the moist Irish climate, as the trenches formed by turning in the sods provided drainage. It allowed potatoes to be grown in bogs (peat swamps) and on otherwise unfarmed mountain slopes.
Heavy ploughs In the basic mould-board plough, the depth of cut is adjusted by lifting against the runner in the furrow, which limited the weight of the plough to what a ploughman could easily lift. This limited the construction to a small amount of wood (although metal edges were possible). These ploughs were fairly fragile and unsuitable for 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 the use of a larger mould-board faced in metal. These
heavy ploughs led to greater food production and eventually a marked population increase, beginning around AD 1000. Before the
Han dynasty (202 BCAD 220), Chinese ploughs were made almost wholly of wood except for the iron blade of the ploughshare. These were V-shaped iron pieces mounted on wooden blades and handles. By the Han period the entire ploughshare was made of
cast iron. These are the earliest known heavy, mould-board iron ploughs. Several advancements such as the three-shared plough, the plough-and-sow implement, and the harrow were developed subsequently. By the end of the
Song dynasty in 1279, Chinese ploughs had reached a state of development that would not be seen in
Holland until the 17th century. The Romans achieved a heavy-wheeled mould-board plough in the late 3rd and 4th century AD, for which archaeological evidence appears, for instance, in
Roman Britain. The Greek and Roman mould-boards were usually tied to the bottom of the shaft with bits of rope, which made them more fragile than the Chinese ones, and iron mould-boards did not appear in Europe until the 10th century. The first indisputable appearance after the Roman period is in a northern Italian document of 643. Old words connected with the heavy plough and its use appear in
Slavic, suggesting possible early use in that region. General adoption of the
carruca heavy plough in Europe seems to have accompanied adoption of the
three-field system in the later 8th and early 9th centuries, leading to improved agricultural productivity per unit of land in northern Europe. This was accompanied by larger fields, known variously as
carucates, ploughlands, and plough gates.
Improved designs The basic plough with coulter, ploughshare and mould board remained in use for a millennium. The basic heavy plough worked well in the Northern European soil. It was strong enough to tear up the soil so that cross-ploughing was not needed. Because of this, and the fact that heavy ploughs needed up to eight oxen to pull, the fields became long and narrow. Too many oxen were difficult to turn frequently. Also, the weaker, ard (or scratch) plough necessitated a short and square-shaped field. Major changes in design spread widely in the
Age of Enlightenment, when there was rapid progress in design. Joseph Foljambe in
Rotherham, England, in 1730, used new shapes based on the Rotherham plough, which covered the mould board with iron. Unlike the heavy plough, the Rotherham, or Rotherham swing plough consisted entirely of the coulter, mould board and handles. It was much lighter than earlier designs and became common in England. It may have been the first plough widely built in factories and commercially successful there. In 1789
Robert Ransome, an
iron founder in
Ipswich, started casting ploughshares in a disused malting at St Margaret's Ditches. A broken mould in his foundry caused molten metal to come into contact with cold metal, making the metal surface extremely hard. This process, chilled casting, resulted in what Ransome advertised as "self-sharpening" ploughs. He received patents for his discovery.
James Small further advanced the design. Using mathematical methods, he eventually arrived at a shape cast from a single piece of iron, an improvement on the
Scots plough of
James Anderson of Hermiston. A single-piece cast-iron plough was also developed and patented by
Charles Newbold in the United States. 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. In 1833 John Lane invented a steel plough. Then in 1837
John Deere introduced a
steel plough; it was so much stronger than iron designs that it could work soil in US areas previously thought unsuitable for farming. Improvements on this followed developments in metallurgy: steel coulters and shares with softer iron mould boards to prevent breakage, the chilled plough (an early example of
surface-hardened steel), and eventually mould boards with faces strong enough to dispense with the coulter. By the time of the early 1900s, the steel plough had many uses, shapes and names. The "two horse breaking plough" had a point and wing used to break the soil's surface and turn the dirt out and over. The "shovel plough" was used to lay off the rows. The plough was usually worked clockwise around each land, ploughing the long sides and being dragged across the short sides without ploughing. The length of the strip was limited by the distance oxen (later horses) could comfortably work without rest, and their width by the distance the plough could conveniently be dragged. These distances determined the traditional size of the strips: a
furlong, (or "furrow's length", ) by a
chain () – an area of one acre (about 0.4 hectares); this is the origin of the
acre. The one-sided action gradually moved soil from the sides to the centre line of the strip. If the strip was in the same place each year, the soil built up into a ridge, creating the
ridge and furrow topography still seen in some ancient fields.
Turn-wrest plough The turn-wrest plough allows ploughing to be done to either side. The mould board is removable, turning to the right for one furrow, then being moved to the other side of the plough to turn to the left. (The coulter and ploughshare are fixed.) Thus adjacent furrows can be ploughed in opposite directions, allowing ploughing to proceed continuously along the field and so avoid the ridge–furrow topography.
Reversible plough The reversible (or roll-over) plough has two mould-board ploughs mounted back to back, one turning right, the other left. While one works the land, the other is borne upside-down in the air. At the end of each row the paired ploughs are turned over so that the other can be used along the next furrow, again working the field in a consistent direction. These ploughs date back to the days of the steam engine and the horse. In almost universal use on farms, they have right and left-handed mould boards, enabling them to work up and down the same furrow. Reversible ploughs may either be mounted or semi-mounted and are heavier and more expensive than right-handed models, but have the great advantage of leaving a level surface that facilitates seedbed preparation and harvesting. Very little marking out is necessary before ploughing can start; idle running on the headland is minimal compared with conventional ploughs. Driving a tractor with furrow-side wheels in the furrow bottom provides the most efficient line of draught between tractor and plough. It is also easier to steer the tractor; driving with the front wheel against the furrow wall will keep the front furrow at the correct width. This is less satisfactory when using a tractor with wide front tyres. Although these make better use of the tractor power, the tyres may compact some of the last furrow slice turned on the previous run. The problem is overcome by using a furrow widener or longer mould board on the rear body. The latter moves the soil further towards the ploughed land, leaving more room for the tractor wheels on the next run. Driving with all four wheels on unploughed land is another solution to the problem of wide tyres. Semi-mounted ploughs can be hitched in a way that allows the tractor to run on unbroken land and pull the plough in correct alignment without any sideways movement (crabbing).
Riding and multiple-furrow ploughs Early steel ploughs were walking ploughs, directed by a ploughman holding handles on either side of the plough. Steel ploughs were so much easier to draw through the soil that constant adjustment of the blade to deal with roots or clods was no longer necessary, as the plough could easily cut through them. Not long after that the first riding ploughs appeared, whose wheels kept the plough at an adjustable level above the ground, while the ploughman sat on a seat instead of walking. Direction was now controlled mostly through the draught team, with levers allowing fine adjustments. This led quickly to riding ploughs with multiple mould boards, which dramatically increased 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. Ploughs with two or more furrows call for more than two horses, and usually one or more have to walk on the ploughed sod, which is hard going for them and means they tread newly ploughed land down. It is usual to rest such horses every half-hour for about ten minutes.
Improving metallurgy and design John Deere, an
Illinois blacksmith, noted that ploughing many sticky, non-sandy soils might benefit from modifications in the design of the mould board and the metals used. A polished needle would enter leather and fabric with greater ease and a polished pitchfork also require less effort. Looking for a polished, slicker surface for a plough, he experimented with portions of saw blades, and by 1837 was making polished, cast steel ploughs.
Balance plough The invention of the mobile
steam engine allowed steam power to be applied to ploughing from about 1850. In Europe, soil conditions were often too soft to support the weight of a
traction engine. Instead, counterbalanced, wheeled ploughs, known as
balance ploughs, were drawn by cables across the fields by pairs of
ploughing engines on opposite field edges, or by a single engine drawing directly towards it at one end and drawing away from it via a pulley at the other. The balance plough had two sets of facing ploughs arranged so that when one was in the ground, the other was lifted in the air. When pulled in one direction, the trailing ploughs were lowered onto the ground by the tension on the cable. When the plough reached the edge of the field, the other engine pulled the opposite cable, and the plough tilted (balanced), putting the other set of shares into the ground, and the plough worked back across the field. One set of ploughs was right-handed and the other left-handed, allowing continuous ploughing along the field, as with the
turn-wrest and
reversible ploughs. The man credited with inventing the ploughing engine and associated balance plough in the mid-19th century was
John Fowler, an English agricultural engineer and inventor. However the Fisken brothers demonstrated (and went on to patent) a balance plough about 4 years before Fowler. One notable producer of steam-powered ploughs was
J.Kemna of Eastern Prussia, who became the "leading steam plough company on the European continent and penetrated the monopoly of English companies on the world market" at the beginning of the 20th century.
Stump-jump plough The
stump-jump plough was invented in 1876 by Australian
Richard Bowyer Smith alongside his brother
Clarence Herbert Smith. It is designed to break up new farming land that contains tree stumps and rocks expensive to remove. It uses a moveable weight to hold the ploughshare in position. When a tree stump or rock is encountered, the ploughshare is thrown up clear of the obstacle, to avoid breaking its harness or linkage. Ploughing can continue when the weight is returned to the earth. s in Australia, c. 1900 A simpler, later system uses a concave disc (or pair of them) set at a wide angle to the direction of progress, using a concave shape to hold the disc into the soilunless something hard strikes the circumference of the disc, causing it to roll up and over the obstruction. As this is dragged forward, the sharp edge of the disc cuts the soil, and the concave surface of the rotating disc lifts and throws the soil to the side. It does not work as well as a mould-board plough (but this is not seen as a drawback, because it helps to fight wind erosion), but it does lift and break up the soil (
see disc harrow).
Modern ploughs Modern ploughs are usually multiple reversible, mounted on a tractor with a
three-point linkage. These commonly have from two to as many as seven mould boardsand semi-mounted ploughs (whose lifting is assisted by a wheel about halfway along their length) can have as many as 18. The tractor's hydraulics are used to lift and reverse the implement and to adjust furrow width and depth. The plougher still has to set the draughting linkage from the tractor, so that the plough keeps the proper angle in the soil. This angle and depth can be controlled automatically by modern tractors. As a complement to the rear plough a two or three mould-board plough can be mounted on the front of the tractor if it is equipped with front three-point linkage. ==Specialist ploughs==