It is very well known that a young orchard will not, usually, flourish on the site of an old one; for the older trees are supposed to have withdrawn from the soil certain elements necessary to their growth; and as necessary to the growth of the young tree, should it be planted there. There is no “like” or “dislike” of the soil to the tree; it is a plain case of starvation. The tree needs, and the soil cannot supply certain elements of its wood.
But if, after a plant has abstracted from the soil certain ingredients, the whole plant is decomposed and returned to the earth, the soil repossesses itself of the lost elements, and is ready to yield them up again to a plant of the same kind. If the straw of wheat be burned upon the field, annually, the soil would yield fine crops for a thousand successive years, that is so far as the _straw is concerned_. But if the grain is removed, and nothing resupplies the drain of phosphates which it makes from the soil, the soil will in due time, according to the original quantities in the soil, cease to yield _grain_, although the straw may be admirable. But if both straw and kernel were every year burned upon the field, as grass and its seed is upon the prairies, wheat would grow for a thousand years in succession. The same is true of corn, of potatoes, and of any annual crop. When the annual growth is restored to the soil, it is repossessed of all its treasure which had been loaned for a season. If a part of the crop is removed, the soil is poorer by just so much as the portion removed contained within it of the elements necessary to that crop, and it must be restored artificially, _i. e. by manuring_; or by allowing the earth to prepare (by disintegration or decomposition of its minerals) a new supply; _i. e. by fallowing_. A forest will grow for ages on the same spot, for it returns annually its leaves, and, gradually, by force of accidents and the elements, its twigs, branches, trunks, etc., to the soil again. But let the whole product be gradually removed, and the soil would soon be unable to supply the trees their nourishment, except in cases where the soil was very rich in the materials of growth. The forests of Germany, like our mines, are under the management of the government. It was customary, for a time, to allow the peasants the use of the _twigs_ and _smaller branches_; but analysis has shown that in these, especially, resides the large proportion of potash entering into the composition of trees; the annual removal of it debilitated the trees to an extent that obliged the Conservators to change their mode of proceeding.