PLOW, PLOWING (AS. /doh, OHG. pfluoh, (der. Pflug, plow; connected with Longobardic p/oruni. and possibly with Gk. 7X(oxiv, glorhin, projecting point). In all countries where agri culture is in an advanced state, the first agricul tural operation in order and importance is the breaking up of the soil by inverting the upper stratum of earth upon which the plants grow. Such an operation also buries and destroys weeds; leaves the surface clean, unencumbered, and in a condition favorable for weathering; in creases the storage capacity of the soil for water; but also assists percolation and thus aids in dry ing and warming the soil.
To the unobservant, the plow seems a simple and even primitive tool; yet it is the product of slow evolution and much mechanical skill. The plow in primitive form probably antedates his tory. The Old Testament mentions plows shod with iron or bronze, but except in Western Eu rope and America little progress has been made in improving the implement since the time of Herodotus. One of the earliest types of plows is shown in Fig. 1; a type of the ordinary modern plow in its simple form in Fig. 2. As will be seen, the modern plow consists of several parts _ a beam, by which the plow is drawn, which may be of wood or metal; two handles, usually wood, for guiding. To the end of the beam a clevis or bridle is attached for convenience in hitehing the team and regulating the depth and width of and near the outer end a small adjust able wheel ( frequently omitted) for assisting in steadying the plow and regulating the depth of the furrow. Behind this is a coulter for cut ting the furrow slice at the side. This coulter takes various forms—a miniature plow or joint er, a stout iron knife, or a revolving disk with sharp edge. Back of the coulter is the plow proper, consisting of a strong cast-iron frame (standard or sheath) firmly fastened to the beam and braced by the handles in rear. To this frame is attached a pointed share for cutting the fur row* slice at the bottom, a mold-board for turning the furrow slice. and the land-side opposite the mold-board, which presses against the side of the furrows and help; to steady the plow.
The first patent for a plow- is said to have been obtained by Joseph Foljamb in 1730. and Jethro Tull about this time invented a plow de signed especially to pulverize the soil thoroughly.
an idea embodied in modern plows of the best type. Figure 3 shows the Rotherham plow used in Holland at the beginning of the eighteenth century, and afterwards introduced into England.
In attempts to improve the plow the mold-board, which raises and turns the furrow slice and which appeared in the plows of the Netherlands during the seventeenth century, has probably received more attention than any other single part. Thomas Jefferson, who published his views in 179S, and .James Small in 1502, were among the first to attempt to establish the proper lines of the mold-board upon a mathematical basis.
As determined by the shape of the mold-board, ordinary plows are of two main types, (1) 'sod plows' with long sloping mold-board which turn a narrow, flat furrow without pulver izing the furrow slice, but which bury vegetation, manure, etc., effectually: and (2) the 'stubble plows.' with short, steep,merhanging mold-board, which break up the furrow• slice and pulverize the soil. English are gi nerally of the first type. The modern American plow• is generally of the second type. although of the first type are made :tad used to a considerable extent for special purpose. in America. it may he said to date from September 1, 1319, when Wood of Scipio, N NV York, took out a patent for an improved cast-iron plow having the mold board (of pulverizing type), share. and land side east in three separate pieces so that they could be replaced by new parts when worn. Ander son found that 55 per cent. of the draught of the plow is consumed in cutting the furrow slice, 12 per cent. in turning it, and 33 per cent. by the sole and land-side. Since such a small per centage of the l'In.rgy required in plowing is con sumed by the mold-board, it would seem to be economy to make this of such form that it will disintegrate the furrow• slice as completely as possible. Such breaking of the furrow slice makes it easier for the tillage implements follow ing the plow to fine the soil thoroughly without disturbing the buried sod and vegetation. A further important advantage of the work of such plows is the inereased opportunity afforded to the soil for weathering.