=Place in the Rotation.=--All the varieties of clover discussed in this volume may be grown in certain rotations. Their adaptation for this use, however, differs much. This increases as the natural period of the life of the plant lessens and _vice versa_. Consequently, the medium red variety, the mammoth, the crimson, the Japan and the burr varieties stand high in such adaptation. The alsike, living longer, is lower in its adaptation, and alfalfa, because of its long life, stands lowest in this respect. The small, white variety is almost invariably grown or found growing spontaneously along with grasses, hence no definite place has been or can be assigned to it in the rotation. Sweet clover being regarded by many as a weed has not had any place assigned to it in a regular rotation, although in certain localities it may yet be grown for purposes of soil renovation. (See page 306.) All these crops are leguminous without any exception. This fact is of great significance where crops can be rotated. They have power to gather nitrogen from the air and store it in the soil in tubercles which form on their roots, in all soils in which they produce a vigorous growth. This fact indicates where they should come in the rotation. They should be grown with a view to gather food for other crops made to follow them, which have not the same power. They should, therefore, be made to precede such crops as the small cereals, corn, the sorghums, the millets and cotton. But since these clover plants have the power to bring nitrogen from the air, it must not be supposed that they will grow with sufficient vigor in soils destitute of this element. They must be able to appropriate enough from the seed soil to give them a good start before they can draw nitrogen from the air, hence, though they may be made to follow almost any kind of crop, it may sometimes be necessary to apply some nitrogenous fertilizer before they will make a vigorous growth. The clovers, unless in the case of some of the smaller varieties, are more commonly sown to provide hay than pasture in the first crops obtained from them. The value of the hay is increased or lessened in proportion as weeds are present. To insure cleanliness in the hay crop, therefore, the system which aims to sow clover seed on land to which clean cultivation has been given while growing on them a cultivated crop, as corn or field roots, meets with much favor. The mechanical condition of the soil immediately after growing these crops also favors the vigorous growth of the young clover plants, more especially when they are sown upon the surface of the land after some form of surface cultivation, rather than upon a surface made by plowing the land after cultivation has been given to it, but to this there may be some exceptions.