by overmuch shading from the
grain when it grows rankly and thickly, and to such an extent that they
perish; 2. When the grain lodges, as it frequently does, on rich
ground, the clover plants underneath the lodged portions succumb from
want of light; 3. Where the supply of moisture is low, in the struggle
for the same between the stronger plants of the nurse crop and the
weaker plants of the clover, the former secures the larger share. As a
result, when the nurse crop is harvested, should the weather prove hot
and dry beyond a certain degree, the clover plants will die. This is an
experience not at all uncommon on the loose prairie soils of the upper
Mississippi basin.

Injury from crowding and overshading may be prevented, or at least
lessened, by pasturing the nurse crop with sheep for a time, at an early
stage in its growth. The lodging of the grain may also be prevented by
the same means. Injury from drought may also be lessened by cutting the
crop at the proper stage of advancement, and making it into hay, as in
the ripening stage of growth it draws most heavily on the moisture in
the soil. The oat crop is the most suitable for being thus dealt with.

Clover seed may be sown with any of the small cereal grains as a nurse
crop, but not with equal advantage. Rye, barley, wheat and oats are
probably suitable in the order named. Rye shades less than wheat and
oats and is harvested early; hence, its suitability for a nurse crop.
Winter rye and winter wheat are more suitable than spring varieties of
the same, since, on these the crop may usually be sown earlier, and the
soil is likely to lose less moisture from surface evaporation. The
marked suitability of barley as a nurse crop arises chiefly from the
short period which it occupies the ground. Nor is the shade so dense as
from grains that grow taller. Oats are the least suitable of all the
crops named as a nurse crop, since they are characterized by a dense
growth of leaves, which shut out the sunlight too much when the growth
is rank. Notwithstanding, the oat crop may well serve such an end when
sown thinly and cut for hay. Mixed grains grown together, as, for
instance, wheat and oats, or a mixture of the three, answer quite as
well for a nurse crop as clover and oats. The objection to them for such
use arises from the fact that they are frequently sown more thickly than
grain sown alone.

Clover may also be sown with flax or millet or mixed grains grown to
provide