States.

With reference to adaptation to soils, medium and mammoth clover grow
best on upland clay loam soils, such as have sustained a growth of
hardwood timber, and on the volcanic ash soils of the Western mountain
valley. Alfalfa flourishes best on those mountain valley soils when
irrigated, or when these are so underlaid with water as to furnish the
plants with moisture. Alsike clover has much the same adaptation to
soils as the medium and mammoth varieties, but will grow better than
these on low-lying soils well stored with humus. Crimson clover has
highest adaptation for sandy loam soils into which the roots can
penetrate easily. Small, white clover has adaptation for soils very
similar to that of alsike clover. Japan clover and burr clover will grow
on almost any kind of soil, but on good soils the growth will, of
course, be much more vigorous than on poor soils. Sweet clover seems to
grow about equally well on sandy loams and clay loams, but it has also
much power to grow in stiff clays and even in infertile sands.

=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