CATCH-CROPS. The natural successor to the wasteful fallow of the more primitive farmer is the catch-crop of to-day. Its only alternative, if the ground is to be continuously used, is the system of continuous cropping; and though here and there this has been tried with some success, even with wheat, it is never likely to become a common practice. Now every vegetable or market garden represents a method of catch-cropping wholly substituted for any slowly maturing crop. On the farm the system is less intensive and most of the catch-crops are sown in late summer or in autumn in immediate succession to the main crop. The earliest are meant to provide green food for stock in the winter of the same year, the later in the spring of the next year; and some, including turnips, which sprout a second time, may do both. As a rule, though not always, they follow a corn crop; and are therefore in Britain much more freely grown in the south than in the north, where the corn is often carried too late to give time for the operation, or a good enough prospect of success for the crop. As a matter of habit not wholly due to climate, definite rotations of standard crops are more strictly followed by northern farmers than by southern. Indeed some of the thin, warm, early soils in the south are treated rather like gardens with catch-crops following one another on no definite system. In sheep districts white turnips are often immediately followed by rape, the first supplying winter, and the second summer fodder.
The commonest catch-crops are rye, tares or other vetches, winter barley, winter oats and red clover or trifolium. None requires deep cultivation ; and the trifolium which needs a firm seed bed is usually sown broadcast on the unploughed stubble, which is thereafter thoroughly harrowed. Annual rye grass, vetches and rape, are not infrequently sown in spring, maize and buck-wheat in early summer; and in sheep districts, mustard is sometimes sown three times successively between March and September. The primary objects of catch-cropping are to pro vide food for stock in the leaner seasons and to keep the ground in continuous use, substituting "bastard" fallows for the old "bare" or winter or summer fallows. But the system is much involved with the art of preventing the loss of nitrogen in certain soils in certain climates. Much scientific work on the question is still in progress.