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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). |
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. So 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. |
Heavy volcanic loam soils such as are found in New Zealand require the use of four heavy draught horses to pull a double-furrow plough. Where paddocks are more square than oblong, it is more economical to have horses four wide in harness than two-by-two ahead, so that one horse is always on the ploughed land (the sod). The limits of strength and endurance in horses made greater than two-furrow ploughs uneconomic to use on a farm.[citation needed] |
Amish farmers tend to use a team of about seven horses or mules when spring ploughing. As Amish farmers often cooperate on ploughing, teams are sometimes changed at noon. Using this method, about 10 acres (4.0 ha) can be ploughed per day in light soils and about 2 acres (0.81 ha) in heavy soils.[citation needed] |
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. The energy required was lessened, which enabled the use of larger ploughs and more effective use of horse power. |
The advent 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 with 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.[30] One notable producer of steam-powered ploughs was J.Kemna of Eastern Prussia, who became the "leading steam plow company on the European continent and penetrated the monopoly of English companies on the world market"[31] at the beginning of the 20th century. |
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 14 bottoms were used. Often these 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 internal combustion engines appeared, they lacked the comparable strength and ruggedness. Only by reducing the number of shares could the work be completed. |
The stump-jump plough, an Australian invention of the 1870s, 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. |
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 soil – unless 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 so 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 are usually multiply reversible, mounted on a tractor with a three-point linkage.[32] These commonly have from two and to as many as seven mould boards – and 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 ploughman 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. |
The chisel plough is a common tool for deep tillage (prepared land) with limited soil disruption. Its main function is to loosen and aerate the soils, while leaving crop residue on top. This plough can be used to reduce the effects of soil compaction and to help break up ploughpan and hardpan. Unlike many other ploughs, the chisel will not invert or turn the soil. This feature has made it a useful addition to no-till and low-till farming practices that attempt to maximise the erosion-preventing benefits of keeping organic matter and farming residues present on the soil surface throughout the year. Thus the chisel plough is considered by some[who?] to be more sustainable than other types of plough, such as the mould-board plough. |
Chisel ploughs are becoming more popular as a primary tillage tool in row-crop farming areas. Basically the chisel plough is a heavy-duty field cultivator intended to operate at depths from 15 cm [6 in] to as much as 46 cm [18 in]. However some models may run much deeper. Each individual plough or shank is typically set from nine inches (229 mm) to twelve inches (305 mm) apart. Such a plough can meet significant soil drag, so that a tractor of sufficient power and traction is required. When planning to plough with a chisel plough, it is important to note that 10–20 horsepower (7.5 to 15 kW) per shank will be required, depending on depth.[citation needed] |
Pull-type chisel ploughs are made in working widths from about 2.5 m (8 ft) up to 13.7 m (45 ft). They are tractor mounted, and working depth is hydraulically controlled. Those more than about 4 m (13 ft) wide may be equipped with folding wings to reduce transport width. Wider machines may have the wings supported by individual wheels and hinge joints to allow flexing of the machine over uneven ground. The wider models usually have a wheel each side to control working depth. Three-point hitch-mounted units are made in widths from about 1.5 m to 9 m (5–30 ft). |
Cultivators are often similar in form to chisel ploughs, but their goals are different. Cultivator teeth work near the surface, usually for weed control, whereas chisel plough shanks work deep under the surface. So cultivation takes much less power per shank than does chisel ploughing. |
A ridging plough is used for crops such as potatoes or scallions grown buried in ridges of soil, using a technique called ridging or hilling. A ridging plough has two back-to-back mould boards cutting a deep furrow on each pass with high ridges either side. The same plough may be used to split the ridges to harvest the crop. |
This variety of ridge plough is notable for having a blade pointing towards the operator. It is used solely by human effort rather than with animal or machine assistance and pulled backwards by the operator, requiring great physical effort. It is particularly used for second breaking of ground and for potato planting. It is found in Shetland, some western crofts, and more rarely Central Scotland, typically on holdings too small or poor to merit the use of animals. |
The mole plough allows under-drainage to be installed without trenches, or breaks up the deep impermeable soil layers that impede it. It is a deep plough with a torpedo or wedge-shaped tip and a narrow blade connecting it to the body. When dragged over ground, it leaves a channel deep under it that acts as a drain. Modern mole ploughs may also bury a flexible perforated plastic drain pipe as they go, making a more permanent drain – or may be used to lay pipes for water supply or other purposes. Similar machines, so-called pipe-and-cable-laying ploughs, are even used under the sea for laying cables or for preparing the earth for side-scan sonar in a process used in oil exploration.[citation needed] |
A simple check can be made to find if the subsoil is in the right condition for mole ploughing. Compact a tennis ball-sized sample from moling depth by hand, then push a pencil through. If the hole stays intact without splitting the ball, the soil is in ideal condition for the mole plough. |
Heavy land requires draining to reduce its water content to a level efficient for plant growth. Heavy soils usually have a system of permanent drains, using perforated plastic or clay pipes that discharge into a ditch. Mole ploughs The small tunnels (mole drains) that mole ploughs form lie at a depth of up to 950 mm (3 in) at an angle to the pipe drains. Water from the mole drains seeps into the pipes and runs along them into a ditch. |
Mole ploughs are usually trailed and pulled by a crawler tractor, but lighter models for use on the three-point linkage of powerful four-wheel drive tractors are also made. A mole plough has a strong frame that slides along the ground when the machine is at work. A heavy leg, similar to a sub-soiler leg, is attached to the frame and a circular section with a larger diameter expander on a flexible link is bolted to the leg. The bullet-shaped share forms a tunnel in the soil about 75 mm diameter and the expander presses the soil outwards to form a long-lasting drainage channel. |
The para-plough, or paraplow, loosens compacted soil layers 3 to 4 dm (12 to 16 inches) deep while maintaining high surface residue levels.[33]It is primary tillage implement for deep ploughing without inversion. |
The spade plough is designed to cut the soil and turn it on its side, minimising damage to earthworms, soil microorganism and fungi. This increases the sustainability and long-term fertility of the soil. |
Using a bar with square shares mounted perpendicularly and a pivot point to change the bar's angle, the switch plough allows ploughing in either direction. It is best in previously-worked soils, as the ploughshares are designed more to turn the soil over than for deep tillage. At the headland, the operator pivots the bar (and so the ploughshares) to turn the soil to the opposite side of the direction of travel. Switch ploughs are usually lighter than roll-over ploughs, requiring less horsepower to operate. |
Mould-board ploughing in cold and temperate climates, down to 20 cm, aerates the soil by loosening it. It incorporates crop residues, solid manures, limestone and commercial fertilisers along oxygen, so reducing nitrogen losses by denitrification, accelerating mineralisation and raising short-term nitrogen availability for turning organic matter into humus. It erases wheel tracks and ruts from harvesting equipment. It controls many perennial weeds and delays the growth of others until spring. It accelerates spring soil warming and water evaporation due to lower residues on the soil surface. It facilitates seeding with a lighter seed, controls many crop enemies (slugs, crane flies, seedcorn maggots-bean seed flies, borers), and raises the number of "soil-eating" earthworms (endogic), but deters vertical-dwelling earthworms (anecic). |
Ploughing leaves little crop residue on the surface that might otherwise reduce both wind and water erosion. Over-ploughing can lead to the formation of hardpan. Typically, farmers break that up with a subsoiler, which acts as a long, sharp knife slicing through the hardened layer of soil deep below the surface. Soil erosion due to improper land and plough utilisation is possible. Contour ploughing mitigates soil erosion by ploughing across a slope, along elevation lines. Alternatives to ploughing, such as a no till method, have the potential to build soil levels and humus. These may be suitable for smaller, intensively cultivated plots and for farming on poor, shallow or degraded soils that ploughing would further degrade. |
Back side of a 100 Mark banknote issued 1908 |
1975 Italian Lira coin |
Robert Burns statue, Schenley Park, Pittsburgh |
The Gefion Fountain in Copenhagen |
Henry Herbert La Thangue, The Last Furrow, 1895 |
Ploughing in the Nivernais by Rosa Bonheur (1849) |
Plough-usage was revolutionized with the advent of steam-locomotives (as seen in this German 1890's watercolor) |