Crop rotation

1246. The necessity for a rotation of crops was supposed by De Candolle and some other foreign botanists to arise from every plant in the course of its growth throwing off a quantity of excrementitions matter which was poisonous to plants of its own nature, though it was not at all injurious to other plants, particularly if they chanced to be of quite a different kind. Thus ground in which turnips had grown was believed to be poisonous for another crop of turnips the next year, though it was quite suitable for a crop of peas; and the ground which had produced peas was found the next year to do best for potatoes, and so on.