Ploughs

PLOUGHS The primary object of ploughing is to break up the soil to form a The plough does this by cutting and inverting the soil in slices or furrows 9 to 14in. wide and to a depth of 4 to 6in. or sometimes more. The inversion of the furrow slice exposes a large area of fresh soil to the influences of the weather and smothers the crop which is laid under.

In its simplest form the plough consists of a frame or body to which the following parts are attached: (a) handles or stilts used for controlling the plough; (b) beam for hauling the plough, carrying devices for making vertical and horizontal adjustments of the draught ; (c) the share for cutting the bottom of the fur row slice ; (d) the land_ ode which takes the side thrust ; (e) the mouldboard or breast for turning the furrow ; and usually (f) the coulter for cutting the vertical side of the furrow : sometimes this attachment is dispensed with, the side of the furrow then being cut by the shin of the plough. Wheels for carrying and guiding the plough are also attached to the beam. A tail knife or presser may also be attached to the breast to assist in turning the furrow. Coulters are of three kinds : the knife coulter which is suitable for all conditions except where tough surface growth must be cut, when use is made of a ro!iing or disk coulter or skeith, generally with a caster action. In Great Britain the rolling coulter is more generally used with tractors. When ploughing turf land a skim coulter or jointer is used to cut out a small section of the turf and turn it into the furrow bottom. Combined disk and skim coulters are also used.

Frames and beams are usually made of iron or steel, but wood is sometimes used to save expense and weight. Shares may be made of cast iron, chilled underneath to make them self-sharpening, or of soft-centre steel; i.e., surface layers of hard carbon steel welded on to a mild steel centre : this provides both the necessary strength and a surface which will take a high polish. Wrought iron shares are often used where the soil contains rocks and stones. Landsides need a highly polished surface and are made of cast iron or steel. Breasts for general purpose ploughs are made of cast iron or mild steel ; cast iroh is the harder metal and is more suitable for gritty or sandy soils, while mild steel is more suitable for heavy land since it scours better. Chilled steel is also coming into use. Digger breasts, being short and concave, must be made of very hard highly polished metal such as chilled cast iron, cast steel or chilled steel, otherwise the sdl is apt to lodge in the hollow of the breast. Wood is still used in certain districts or for special pur poses, as on the strong land of Kent, England : and a large variety of materials, even plaster of parts, has been experimented with for overcoming unusual soil conditions.

Types of Plough.

Breast ploughs can be divided into three principal types, i.e., lea ploughs or breakers for lea, sod or turf ground with long sloping shares and breasts of gentle curvature to raise the furrows gradually without breaking them; digger ploughs for use in stubble and cultivated ground with short abrupt breasts which break up the furrows as they are turned over; and general purpose ploughs of an intermediate type which are suitable for general use. Ploughs may also be distinguished as walking or riding ploughs, according as the ploughman walks or drives with the plough, and disk ploughs which employ a revolving disk.

The cheapest and simplest of ploughs are those without wheels. They make the most demand upon the skill of the ploughman, however, but are useful on very heavy land where wheels might clog and also among rocks and stumps. Ploughs with one wheel, placed under the beam for regulating the depth of work, are use ful on sloping ground. A plough widely used on the Continent of Europe has a two-wheeled forecarriage which allows the beam a certain amount of free movement, the plough itself being hauled by a pair of chains attached near the frame. One-way ploughs which lay all the furrows in one direction are also common. They render it unnecessary to set out the field in ridges, save time in turning and leave no dead furrows. Balance one-way ploughs, which are much used in parts of England, have two bodies with the shares facing each other connected to a common set of wheels. Other one-way ploughs, such as the "double Brabant" plough, which is very popular on the Continent of Europe, have also two bodies (fixed opposite to each other on the same beam) but are turned over sideways. The most widely used one-way plough has one body and a double-sided breast. It is known by many names, including hillside, reversible, turnwrest, swivel, and is the best for hillside use. It may aptly be termed the "general purpose one-way plough." Ridging ploughs have two flat breasts and a special share and are used with and without wheels for making ridges for potatoes and roots and for earthing up potatoes. Single-furrow riding or sulky ploughs usually have three wheels, one running on the land and two in the furrow, one in front and one behind the plough which takes the driver's weight and the sideways thrust on the breast and reduces the friction on the plough sole. These ploughs are little used in Europe but are common in America and Aus tralia. Riding one-way ploughs are also used in America : they usually have two separate bodies and breasts mounted on the frame-work in such a way that each body may be lifted out of work in turn. Multiple or gang ploughs may be used either with horses or with tractors. In Great Britain a double-furrow walking plough is used in light land districts. In America and Australia riding ploughs with multiple furrows are used : but the standard of work demanded would not be regarded as high in intensively cultivated countries. For light tractors, self-lift or power-lift ploughs are almost universally used. The plough is attached to the tractor by a special hitch which can be regulated to minimize side draught and incorporates a device to release the plough should it strike any obstacle. In this way only one man is required to operate both tractor and plough, which may have two or three furrows. Ploughs are also made for mounting direct on to the tractor frame : they are without transport wheels but may have a land wheel for steadying them while at work. The advantages claimed are lighter draught, shorter headlands and easier turning and reversing. Large riding ploughs with six to twelve furrows are used in America where conditions are favourable and large areas have to be ploughed. These ploughs usually have the bodies flexibly attached to the beam, each body having a separate lever by which its depth of working can be regulated by the ploughman.

Ploughs for Cable Haulage.

Theoretically the cable system is the most efficient method of ploughing since it avoids all un necessary haulage, but in practice this is discounted by the high capital cost of the equipment ; hence the cable system can only be economically employed where large areas, usually heavy land, can be dealt with by one set. Such ploughs are usually made on the balance principle with two sets of bodies so as to avoid turn ing them at the headlands. There are several systems of cable ploughing. The single engine system makes use of anchors and pulleys for directing the cable that hauls the plough backwards and forwards across the field and along the headlands. This system which, it may be noted, has been adopted for electric ploughing, is lower in first cost but slower and less satisfactory than the more popular double-engine system, where an engine is employed at each side of the field. Each engine in turn draws the plough while the other pays out the cable and as the work progresses the engines are moved along the headlands.

Disk ploughs which are very common in America though little used in Great Britain, have revolving concave disks, in place of breasts, and scrapers. They are suitable for use in very hard ground (e.g., dry adobe) and very heavy ground (e.g., sticky or waxy land) when a breast plough will not operate. Generally speaking the draught is heavier and the work inferior to that of a breast plough. They may be used with horses, tractors or cable sets. Subsoil ploughs are used to break up the soil below the furrow bottom without bringing it to the surface, and are an al ternative to deep ploughing in land with shallow top soil and a subsoil which it would be dangerous to bring to the surface. The subsoiling device is usually a tine, though a cartridge-shaped piece of steel may also be used. Mole ploughs are used for draining land with a clay subsoil and have a beam carrying a stout knife coulter to the foot of which a cartridge-shaped piece of steel or "mole" is attached. The mole may be set to work at different depths and by being drawn through the ground compresses the subsoil in its passage, leaving a drainage channel of its own diameter at the re quired depth. The narrow slit cut by the coulter closes up and the water then passes into the drain by percolation. Mole drains must have outlets into a main drain or an open ditch and a natural gradient is essential as they follow the contour of the land. There are a number of mole ploughs suitable for tractor haulage which will cut drains from 15 to i8in. deep, but for deeper work than this it is preferable to use cable haulage as the draught is too great for the average agricultural tractor.