The most serious objection to seeding sweet clover in the spring
without a nurse crop is weeds. In many sections of the country seeds
will take as much water from the soil and make as much or more shade
than a crop of grain. In spite of the fact that sweet clover will
withstand more adverse conditions than red clover or alfalfa, a heavy
growth of weeds will greatly retard the growth of the plants and in
some cases kill most of them. (Fig. 10.) On plats sown in April without
a nurse crop at Arlington, Va., it was necessary to mow weeds five
times during the summer of 1915 in order to keep them partly checked.
Where it is necessary to mow a field so many times the plants are not
only checked or killed, but as much time is required for this work as
would be necessary to harvest a crop of grain. This trouble may be
overcome in part by pasturing the sweet clover the first season, but
even then during wet weather it may be necessary to cut the weeds at
least once before the plants become well enough established to turn
live stock on the field. The plants should at no time be clipped closer
than 5 inches from the ground.
After a field of sweet clover has become well established, it may
be pastured throughout the summer and fall. Close grazing should be
avoided during the summer, or the plants may be killed, but they may
be pastured fairly close to the ground in the autumn, as it does not
appear as necessary to provide a winter covering as is the case with
red clover. Close pasturing or clipping late in the fall has had a
marked effect on the growth of the plants the following spring on some
fields and no apparent effect on the stand and growth of the plants
on other fields. A portion of a field in Livingston County, Ill., was
clipped close to the ground in the late fall of 1915. On June 1, 1916,
the stand was somewhat heavier on the unclipped part of the field.
More noticeable than the thickness of the stand was the fact that the
plants on the unclipped portion were 8 to 10 inches higher than those
on the clipped area. It is reasonable to believe that plants going into
the winter with no protection are more likely to be injured than those
having some protection.
On the other hand, many fields in different parts of the country have
been closely clipped or pastured in the late fall with no noticeable
injury. Because of the value of the hay or pasturage in the late summer
and autumn of the year of seeding, it is strongly recommended that the
first year's growth be utilized. If the field be cut for hay it is
well to leave a 4-inch or 5-inch stubble, as this will serve to catch
drifting snow during the winter, thereby adding to the protection
against winterkilling. If the field is not pastured the first season
and weeds are not troublesome, a cutting of hay may be made when growth
ceases in the fall.
[Illustration: Fig. 10.--White sweet-clover plant (at the left),
showing the effect of a heavy growth of weeds. Had the weeds not been
present the plant at the left should have been larger than the one
at the right, as the seed was sown two weeks earlier and the other
conditions for growth were ideal. Four-fifths of the plants on the plat
which had a heavy growth of weeds were entirely killed.]
When sweet clover is seeded with grain, moisture conditions should
serve to determine whether the grain should be permitted to ripen or
be cut for hay. When untimely droughts appear the plants may be killed
if the grain is not cut as early as possible.
In the South and in some sections of the Eastern and North-Central
States where the soil contains an abundance of limestone and is well
inoculated, a cutting of hay may usually be obtained after a grain
crop has been harvested. In other sections of the North in only
exceptionally favorable weather will more than pasturage be obtained
after the grain is cut.