PLOUGHING. The act of turning over the soil by means of the plough. Trench ploughing is effected by the plough passing twice along the same furrow ; the first time for the purpose of throwing the surface soil into the bottom of the furrow ; and the second time for raising a furrow-slice from under that which had been already turned over, and raising it up, cke., turning it upon the first furrow-slice, by means of which the surface soil is entirely buried, and a stra tum of subsoil laid over it: thus effect ing in the field what trenching with the spade does in the garden. Trench ploughing can only be employed with advantage where the subsoil is naturally dry and of good quality, or where it has been rendered so by draining and subsoil ploughing; for bad subsoil brought to the surface would be unfit for receiving seeds or plants.
The alteration produced upon the capa bility of land, by ploughing, is very great: the tenacity of soils is broken up, the particles separated, drainage and aeration more perfect. The absorbent power of the clay is brought into action, and the gaseous matter furnished by the atmospheric dews and rain is more per fectly retained. As a consequence of a new surface of earth being brought up, the ammonia carbonic and nitric acids which exist in the air, are retained and kept for the future use of the crop.- Ma nures, also, for the same reason, are bet ter absorbed. Worms and insects are thrown out, are thereby exposed to the element, and destroyed in great number, which, if such did not occur, would in fest the growing crop of next year, and perhaps completely ruin it.
The furrows of clay soils should be turned over at an angle of 45°, and the depth of the furrow-slice should be two thirds of its width : thus, a furrow 6 in ches deep should be 9 inches wide, or if 8 inches deep, 12 inches wide. This
allows the furrows to lie equally and evenly. It' the subsoil be similar to the surface, or be not too light, ploughing can hardly be carried too deep—generally 12 inches, for the usual tillage crops, is a depth to which the plough may be gra dually carried. For gardens it may be carried to 15 or 18 inches. Whatever is the depth of the surface soil, the plough ought to turn it up completely ; and, what is boyond that, may be loosened by the subsoil plough. The cultivator is used very often in this country as a substitute for the plough. Even with the most re cent improvement in this instrument, any quantity of land ploughed is a great tax on the strength of animals. Thus, a pair of horses may plough three-fourths of an acre of light soil per day, and one half of stiff soil. If the furrow-slide is 9 inches, an acre is 11 miles of furrows, without turning, equal to another mile ; for there are 6,272,640 square inches in an acre, and 77,440 squares of 9 inches in an acre, and this, by 7040, the number of 9 inches in a mile, goes 11 times. If the slide were 10 inches, the plough would travel 9.9 miles, and if 8 inches, 12.375 miles. Ploughing is, therefore, severe labor for men and horses. In spade culture, if a man turn over 7 inches each time, or 49 square inches, the amount is equal to 128,000 spades, to be turned in an acre.