The most important implement of tillage is the plow, which performs a similar job to the spade in that it loosens the oversoil, breaking it up and exposing new surfaces to the atmosphere. At the same time it turns the soil over, burying any trash. A modern plow can turn more soil in a few minutes than a person working with a spade can in a whole day. A great deal of energy is expended in plowing and a large-furrow plow needs to be attached to a tractor of 100 hp or more.
The development of the plow can be traced back to Neolithic times. Then it was a very simple tool, little more than a suitably forked branch with a sharp point. By Roman times there were three designs: the aratum, or “worker of soil,” which was similar to a Neolithic plow; the ard, which was a beam and spike tool; and the carruca, which had a moldboard to push the soil to one side.
It was not until the sixteenth and seventeenth centuries that the plow underwent any major changes; these were made by the Flemish and Dutch. The move was toward lighter plows and, whereas the older plows had been based on a quadrilateral frame, the new types were triangular.
The Dutch plow was taken to England, improved and patented in 1730 as the Rotherham plow. It still had a wooden frame, beam and handles, but the draft irons, coulter, and share were of iron, and the moldboard and sole were covered with iron plates.
Another development in the seventeeth century was the turnwrest plow. The normal moldboard turned the furrow to one side only so the plow either had to be taken back to the beginning for the next furrow or it had to plow a different strip on its return journey. In two-way plowing on slopes where the soil is always turned uphill, the ability to change the side of the furrow slice, whichever way the plow is facing, is essential. With a turnwrest plow, the moldboard was removed, refitted to the other side, and adjusted to the angle of the coulter.