Title: USDA Leaflet No. 160: Crimson Clover (1938)
Author: Hollowell, Eugene Amos
Language: English
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Transcriber Note

Emphasis is denoted as _Italics_ and =Bold=.



=CRIMSON CLOVER=



LEAFLET No. 160

U.S.DEPARTMENT of AGRICULTURE


Issued June 1938.



=CRIMSON CLOVER=


By E. A. Hollowell, _senior agronomist, Division of Forage Crops and
Diseases, Bureau of Plant Industry_



=Growth and Distribution=


Crimson clover (_Trifolium incarnatum_) is the most important winter
annual legume of the central section of the Eastern States (fig. 1).
Besides being an excellent hay plant and furnishing an abundance of
early spring pasture, it affords protection to the soil during the fall,
winter, and spring, prevents soil washing, and provides green manure for
soil improvement. This legume has the distinct advantage of being a heavy
producer of seed, which can be easily harvested and sown without the use
of expensive machinery.

[Illustration: Figure 1.--Principal crimson clover region of the United
States.]

Crimson clover is a native of Europe and is widely grown in France,
Hungary, and other central and southern European countries. Seed was
introduced into this country as early as 1819, but it was not until 1880
that the plant became of agricultural importance. During the last 6 years
the annual commercial consumption of seed in the United States has ranged
from 2 to 4 million pounds. In addition, large quantities of home-grown
seed are used and handled from farm to farm.

The common name of this clover is derived from the distinctive bright
crimson color of the blossoms. Other common names, such as German clover
and scarlet clover, are frequently heard in different localities. In
general the leaves and stems of crimson clover resemble red clover, but
are distinguished by the rounding of the tips of the leaves and a greater
covering of hair on both leaves and steins. When it is planted in the
fall the leaves develop from the crown and form a rosette, which enlarges
whenever weather conditions are favorable. In late spring flower stems
develop rapidly and terminate their growth with elongated flower heads.
Seed forms and the plant dies with the advent of hot summer weather. The
seed is yellow, slightly larger, and more rounding than red clover seed.



=Adaptation=


Crimson clover is adapted to cool, humid weather and is tolerant of winter
conditions where the temperature does not become severe or too variable.
In this region (fig. 1) it should be planted in late summer or early fall,
since early establishment and growth are favorable to its winter survival.
It will thrive on both sandy and clay soils and is tolerant of ordinary
soil acidity. On extremely poor soils, stands are difficult to obtain and
the growth is stunted. The use of manure and phosphate fertilizers on such
soils will improve the chances of obtaining good stands.

Crimson clover may also be successfully grown as a summer annual in Maine,
northern Michigan, and Minnesota. The winter culture of this clover
may be extended into Kentucky, southern Missouri, and southern Indiana
provided the seed is sown in fertile soil early in August. Production may
be successfully extended southward with an increase of soil fertility and
with seeding delayed until soil-moisture conditions are favorable.



=Seedbed Preparation=


The most important and difficult phase of successful production of crimson
clover is getting a stand. Sufficient soil moisture to germinate the seed
and to establish the seedlings is the greatest factor in obtaining a
stand, which when established usually produces a good crop.

Seedings are usually made in late August or early September between
the rows of cultivated crops. Under such conditions an ideal seedbed
is difficult to prepare, therefore careful preparation is necessary.
Furthermore, the crop plants in the row shade the clover seedlings and
seriously compete with them for the available moisture. Increasing the
distance between the rows and planting the row crop more thinly will
afford better opportunity for the establishment of the clover. When
planted between the rows of other crops, the seed is usually broadcast on
the surface and covered by cultivating or harrowing (fig. 2). Drilling
the seed after the soil surface has been stirred will usually give more
complete stands than broadcasting, and it may be done with a small
one-horse drill. The seed should not be planted more than one-half to
three-fourths of an inch deep, respectively, in clay and sandy soils.

[Illustration: Figure 2.--Seeding crimson clover in corn.]

Crimson clover is often seeded following a grain crop, and this is a
surer method of establishing a stand than planting between the rows of
cultivated crops, providing the seedbed is well prepared. After the grain
crop is removed the soil is plowed or disked and allowed to settle. This
is followed by light harrowing or disking when necessary to kill weed
seedlings. Before the clover is seeded the soil should be firmly packed,
because a loose cloddy seedbed is the forerunner of failure. The seed may
be either drilled or broadcast, but drilling will give more uniform stands.



=Fertilizers=


When the crop is planted on extremely poor soils, good stands and
growth cannot be expected. Such soil conditions may be improved by the
application of manure and phosphate fertilizers or by turning under such
crops as cowpeas, soybeans, or lespedeza. In many soils of low fertility
the use of 50 to 100 pounds per acre of a nitrogen fertilizer will
encourage early seedling growth and establishment. On the fertile soils of
this region crimson clover may be successfully grown without fertilizer,
but on most soils applications of 200 pounds of phosphate fertilizer per
acre are profitable in obtaining stands and vigorous growth (fig. 3). The
use of potash is recommended when a deficiency is known to exist.

[Illustration: Figure 3.--Effect of phosphate application on good soil:
Treated (left); untreated (right).]



=Seed Sources=


Of the total amount of seed normally used approximately 60 percent is
of foreign origin, coming principally from Hungary and France. Most of
the domestic crimson clover seed offered on the market is produced in
south-central Tennessee. While white-flowered strains and others differing
in maturity have been isolated, they are little used. Claims have been
made that locally grown seed is superior to seed from other sources
including that of foreign origin. Further experiments are needed to
determine whether such differences actually exist.



=Rate and Time of Seeding=


Under ordinary conditions 15 to 18 pounds of hulled seed will give good
stands unless there is a deficiency of soil moisture. Depending upon the
amount of foreign material 45 to 60 pounds of unhulled seed is comparable
to a 15-pound seeding rate of hulled seed. Crimson clover may be sown from
the middle of August until October 1 with the expectation of securing a
good stand. The later it is seeded the less growth can be expected and
the more readily winterkilling occurs. The early establishment of the
plants becomes more important as plantings are extended northward. Seeding
crimson clover, if possible, either immediately before or following heavy
rains will increase its chances of making a stand. The spring planting of
crimson clover in or south of the Corn Belt usually results in a short,
stunted growth followed by meager blossoming and an unprofitable yield.



=Inoculation=


In many parts of the crimson clover region it is not necessary to
inoculate the seed; but if clover has not been successfully grown on a
soil, inoculation of the seed is good insurance. If the plants are not
inoculated they will develop slowly, become yellow, and die. Inoculated
plants are able to obtain about two-thirds of their nitrogen from the air
through their root nodules. The plants may be artificially inoculated by
applying pure cultures of the bacteria to the seed or by scattering soil
from a field where inoculated crimson clover has been grown. Two hundred
to three hundred pounds per acre of such soil evenly distributed at
seeding time is sufficient.



=Unhulled Seed=


The use of unhulled seed offers the distinct advantage of increasing
the chance of obtaining thick stands. With the prevalence of dry soil
conditions, light rainfall does not cause the unhulled seed to germinate,
but hulled seed germinates readily and the seedlings may die from lack of
moisture before they can become established.

Its bulky nature makes unhulled seed more difficult to distribute
uniformly than hulled seed. It must be broadcast and may be harrowed in.
It is also difficult to market and is not generally handled by the seed
trade. But farmers can harvest seed for their own use and save the expense
of having it hulled.



=Companion Crops=


Rye, vetch, Italian ryegrass, and fall-sown grain crops are often seeded
with crimson clover. Besides making a valuable addition to the clover
(fig. 4), these companion crops help bolster up a thin stand. Such crops
are seeded from one-half to one-third the normal crop rate and the crimson
clover is seeded at the normal rate. Planting is done at the same time,
but, as a greater depth is required for most of the seed of the companion
crops, two seeding operations are necessary. In Tennessee, farmers often
use a mixture of 5 pounds of red clover and 10 pounds of crimson clover
per acre with excellent results. The first growth of the mixture may be
grazed or harvested for hay or for crimson clover seed, while the second
crop is wholly red clover.

[Illustration: Figure 4.--Crimson clover and rye, an excellent
green-manure combination.]



=Diseases and Insects=


The only serious disease that affects crimson clover is stem rot. The
effect of this disease is seen in the early spring and is characterized by
the plants dying in patches. The stems rot at the surface of the soil or
where they join the crown. The occurrence of continued damp cool weather
during early spring favors the development of the disease. Exclusion of
clover and other legumes from the rotation for a period of 2 to 5 years is
the best control method.

Sandy soils in the southern part of the crimson clover belt are often
infested with nematodes. Nematode injury results in a stunting and
yellowing of the plants and is most prevalent in the southern part of the
region. While the clover-seed chalcid, the pea aphid, and other insects
sometimes become numerous in crimson clover, insects do not ordinarily
cause appreciable damage.



=Utilization=


Crimson clover grows rapidly in early spring and furnishes an abundance
of early grazing (fig. 5). If planted early and an abundant fall growth
is made, the clover may also be grazed during the fall and winter months.
Such a practice has been successfully followed in Tennessee, where crimson
clover has provided the winter pasturage. The grazing, however, should be
restricted to periods when the soil is relatively dry, otherwise damage
may result from trampling. Animals grazing on crimson clover seldom bloat;
however, it is advisable not to turn them into clover fields for the
first time when they are hungry. Bloat is less likely to occur when a
mixture of clover and grass or grain is grazed than when the clover alone
is grazed. As crimson clover reaches maturity the hairs of the heads and
stems become hard and tough. When grazed continuously or when fed as
hay at this stage of maturity large masses of the hairs are liable to
form into hair balls in stomachs of horses and mules. Occasionally the
hair balls are responsible for the death of animals. If small amounts of
other feeds, particularly roughages, are fed along with the clover, the
formation of these balls will be reduced. Cattle, sheep, and swine do not
seem to be affected.

[Illustration: Figure 5.--Crimson clover provides an abundance of early
spring grazing.]

Crimson clover makes excellent hay when cut at the early bloom stage
although the yield may be slightly reduced. For maximum yields it should
be harvested in full bloom. The hay is easily cured either in the swath
or in the windrow. Fewer leaves are lost and less bleaching occurs in
windrowed hay. Although yields as high as 2½ tons per acre are not
uncommon on fertile soil, 1½ to 2 tons is an ordinary production.

Crimson clover is an ideal green-manure crop. For the best result it
should be plowed under 2 to 3 weeks before planting the succeeding crop.
This gives sufficient time for decomposition, which is rapid unless the
crop is mature when plowed under. Occasionally, strips are plowed in which
row crops are planted, allowing the clover between the plowed strips
to mature. Seed may be harvested by hand from the clover between the
row crop, and the remaining clover straw allowed to mat and serve as a
mulch, or the entire plant may be permitted to form a mulch. A volunteer
seeding may be secured in this way, especially in the northern part of
this region, but attempts to follow such a practice should be tried on a
small scale until experience is gained. When used in orchards, crimson
clover is often allowed to mature, after which it is disked into the soil.
Occasionally a volunteer seeding may be obtained in the fall.



=Seed Production=


Crimson clover is a prolific seed-producing plant and yields of 5 to
10 bushels per acre are common, depending upon the thickness of the
stand, the amount of growth that is produced, and the care exercised in
harvesting the seed. The florets are self-fertile, but bees are effective
in tripping and transferring the pollen, with a consequent increase in the
number of seed per head. The placing of colonies of honeybees adjacent
to blooming fields will effectively increase pollination. More seed is
usually produced on soils of medium fertility than on rich soils, since
fertile soils seem to stimulate the growth of stems and leaves at the
expense of flower-head development.

Large yields and ease of harvesting crimson clover seed are the principal
reasons why crimson clover is such an ideal legume crop. Farmers may save
seed with very little expense other than their own labor. When the seed
heads are mature they readily shatter and are easily harvested either by
hand stripping or by using horse-drawn homemade strippers. One bushel of
unhulled seed contains about 2 pounds of hulled seed, and although bulky
in nature, it can be easily stored on the farm until fall.

[Illustration: Figure 6.--Cutting a crimson clover seed crop with a mower
equipped with a bunching attachment.]

When the seed is mature the crop is cut with a mower, which may be
equipped with a bunching or windrowing attachment (fig. 6) or it may be
harvested with a combine. During wet seasons difficulties in combining the
seed from standing plants may be experienced. Under such conditions the
plants may be cut and windrowed and then threshed by the combine from the
windrow. As crimson clover shatters easily when ripe, cutting with the
mower when the heads are damp with dew or rain is recommended. If allowed
to stand too long after it is ripe a beating rain will shatter much of
the seed. After a few days of curing, the seed is hulled with an ordinary
clover huller or a grain separator equipped with hulling attachments. The
less the clover is handled, the less seed will be lost by shattering.

Troublesome weeds are encountered in growing crimson clover seed; field
peppergrass (_Lepidium campestre_) and wintercress (_Barbarea praecox_)
are probably the worst, as their separation from the clover seed is
difficult. Little barley (_Hordeum pusillum_) is objectionable in unhulled
seed, and the use of unhulled seed will naturally increase the prevalence
of this weed.


U. S. GOVERNMENT PRINTING OFFICE: 1938

For sale by the Superintendent of Documents, Washington, D. C. -- Price 5
cents


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=Transcriber Note=


Illustrations moved to avoid splitting paragraphs and closer to references
in the text. Minor typos may have been corrected.





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