1262. All green succulent plants contain saccharine or mucilaginous matter, with woody fibre, and readily ferment. They cannot, therefore, if intended for manure, be used in too fresh a state. Hence the advantage of digging in green crops, whether natural or sown on purpose; they must not, however, be turned in too deep, otherwise fermentation will be prevented by the compression and exclusion of the air. Green crops should be dug in, if it be possible, when in flower, or at the tune the flower is beginning to appear; for it is at this period that they contain the largest quantity of easily soluble matter, and that their leaves are most active in forming nutritive matter. Green crops, pond-weeds, or the parings of hedges or ditches, require no preparation to fit them for manure, nor does any kind of fresh vegetable matter. The decomposition slowly proceeds beneath the soil; the soluble matters are gradually dissolved; and the slight fermentation which goes on, checked by the want of a free communication of air, tends to render the woody fibre soluble without occasioning the rapid dissipation of elastic matter. When old pastures are broken up and turned into garden ground, not only has the soil been enriched by the death and slow decay of the plants which have left soluble matters in the soil, but the leaves and roots of the grasses living at the time, and occupying so large a part of the surface, afford saccharine, mucilaginous, and extractive matters, which very soon become the food of the crop, and, from their gradual decomposition, afford a supply for successive years. The roots of the grass also serve to keep the ground open, and act like so many tubes through which the atmospheric air can reach the roots of the growing plants.
