Forage and Pasture
Forage Management Guides
Self-Study Guide 4: Supplemental Forage Crops
Supplemental forage crops are so named because they are not generally the
main source of forage on Arkansas farms. Rather, they are supplements to the
predominant forage crops grown in a given area. For instance, fescue and
bermudagrass pastures are used by Arkansas farmers to supply most of the forage
needs for a year. Farmers establish fields of these two species with the idea of
keeping them productive for a number of years; however, there are situations
where one or both of these species may not provide adequate forage for a
producer. This dilemma exists most commonly during the summer slump that is
common in fescue pastures and over the winter months. For brief periods, perhaps
30 to 90 days, quickly established annual forage species such as sudangrass,
ryegrass, oats, wheat, rye, pearl millet, and lespedeza can be used to
supplement these permanent forages, thereby reducing the need for homegrown or
purchased hay. Supplemental forages are typically planted on relatively few
acres on a given farm and are intensively used during the short period of their
existence.
The three most common types of supplemental forages in Arkansas are
sudangrass or one of several closely-related alternatives (forage sorghums,
sorghum-sudangrass hybrids, etc.), ryegrass, and small grains (wheat, rye, oats,
barley, and triticale). Sudangrass is planted from early May through mid July
for use during the summer when fescue pastures are dormant. Ryegrass and the
small grains are planted most commonly during late August and September for use
between the time bermudagrass goes dormant in the fall and it renews significant
spring growth.
Using Supplemental Forage Crops While Establishing Permanent Pastures
In addition to their role as forage extenders, supplemental forage crops may
play a key role in helping farmers reestablish permanent fescue or bermudagrass
pastures that have become depleted due to drought, overgrazing, weed pressure,
or other maladies. One of the most common causes of failure during permanent
pasture establishment or reestablishment is that too many animals are permitted
to graze the new stand for too long at critical periods during the establishment
year. Newly seeded fescue and newly sprigged bermudagrass fields also need
protection from the grazing animal during wet periods so that trampling damage
is avoided; in addition, young plants can actually be pulled from the soil by
grazing livestock because the root system of the developing seedlings is not
well developed. For these reasons, a new forage stand should be grazed
cautiously. If the farmer has a supplemental pasture available to use when the
new permanent pastures need rest or become excessively wet, management options
are increased and chances of successful establishment of the permanent pastures
are enhanced.
Let us assume a farmer has four pasture fields of about equal size on his
farm. One pasture (one fourth of his forage acreage) has been killed by drought,
floods, or pests to the point that it is no longer productive. Let us assume
further that the producer has decided to reestablish this damaged pasture by
seeding an improved tall fescue variety in the spring. Depending on the growing
season, production from the new field will likely be only one third to two
thirds that of an older stand. If the overall forage production on the farm was
about adequate for the established livestock enterprise in other years (when the
field to be reseeded was healthy and productive), it will be inadequate during
the year that it is reestablished. Therefore, a potential forage deficit
situation exists that must be managed. Failure to protect the newly reseeded
permanent fescue or bermudagrass pasture from overuse or use under undesirable
weather conditions could result in wasted effort and expense due to stand
failure. A small, well fertilized, and properly-managed supplemental pasture can
make up the forage deficit and provide the producer with an alternative place to
put his cattle when the reestablished pasture needs to be protected.
Possible Supplemental Pastures
I. Sorghum Types
General types of sorghum used as annual forages are sudangrass,
sorghum-sudangrass hybrids, forage sorghums, and hybrid forage sorghums
specifically selected for a one-time harvest as silage. In addition, milo
(sorghum specifically selected for grain production) can also be used for
silage. Common names for these forages are often used interchangeably, thereby
creating confusion.
The term "sudangrass" technically refers to the annual species of sorghum
that has aboveground growth that resembles Johnsongrass. Varieties or hybrids of
this type of sorghum are leafy, fine-stemmed, and regrow quickly after cutting,
relative to other sorghum types. Both varieties and hybrids of sudangrass may be
purchased in Arkansas. The term "sudangrass" is also loosely used by producers
to refer to the more widely used, sorghum sudangrass hybrids. Generally,
sorghum-sudangrass hybrids can be viewed as intermediates between the true
sudangrasses and forage sorghums. Typically, they will yield more than true
sudangrasses, but less than forage sorghums when harvested once. Usually they
have coarser stems than true sudangrasses. As with the sudangrasses, they
actively regrow after the initial harvest. In variety trials at the University
of Arkansas between 1990 and 1993, dry matter yields for sudangrass and
sorghum-sudangrass cultivars ranged widely; yields between 4.6 and 10.6 tons per
acre were observed in Fayetteville. Sudangrasses and sorghum-sudangrass hybrids
are typically drilled or broadcasted at establishment; they can be used as a
hay, silage, or greenchop and are well suited for rotational grazing systems.
Forage sorghums are generally tall types that have suitable characteristics
for establishment as a row crop and harvest as row-crop silage. Hybrid forage
sorghums are also available that have been specifically selected for once-a-year
harvest as silage; they are particularly common in arid areas where conditions
are not favorable for growing corn. Sorghum varieties selected for one-time
harvest as silage can take more than 100 days to mature and are not really
supplemental forages; they are managed much like corn grown for silage and have
little regrowth potential, except in the deep South. Forage sorghums and hybrid
forage sorghums are not good options for most Arkansas producers unless they
have access to land suitable for row-crop production and the equipment necessary
for the establishment, harvest, and storage of row-crop silages.
In general, all sorghum types vary widely with respect to growth and forage
quality characteristics. Producers should spend some time and effort evaluating
varietal options before purchase.
Management practices for sudangrass or sorghum-sudangrass hybrids in Arkansas
are summarized as follows:
1. Choose productive soil that is non droughty.
2. Prepare a compact, weed free seedbed.
3. Make sure fertility does not limit production.
a. Apply P and K fertilizer as prescribed by soil test.
b. Apply 50 to 60 pounds of nitrogen at or shortly after planting.
4. Drill 20 to 25 pounds of seed per acre at a depth of 1 to 1½ inches
between May 1 and July 15. Rates may be increased to 30 to 35 pounds per
acre when broadcast applications are used or when planting for hay. Higher
planting rates will reduce the proportion of stem in the forage. Use earlier
seeding dates in southern Arkansas and later dates in the north. Soil
temperature is very important for good germination; optimum germination
occurs between 68 and 86°F.
5. Graze after plants are 2 feet tall and before flowering. This reduces
the hazard from prussic acid poisoning and allows a quality product to be
harvested. Fifteen percent more forage is available for use under rotational
grazing than in a continuous system. As a rule, sudangrass can supply
grazing for two animal units per acre for 90 days. An animal unit is
considered to be one mature non-lactating cow weighing 1,000 pounds that is
fed at maintenance level.
6. Sudangrass may be cut for hay. It should be cut to leave at least 6
inch stubble for regrowth. This will encourage more vigorous and leafy
regrowth. Three to five tons of hay may be routinely produced per acre.
Twice this amount is possible under more ideal conditions.
7. Under grazing conditions, topdress with 60 pounds of nitrogen every 4
to 5 weeks; similar rates should be applied after each hay cutting. High
rates of nitrogen fertilization can cause excessive nitrate accumulation
when drought stress occurs.
II. Pearl Millet
The production and harvesting practices for pearl millet are similar to those
outlined for sudangrass. Seeding rates are lower (use 15 to 25 pounds per acre),
but the seeding date and depth of seeding are the same as for sudangrass. Pearl
millet may perform better than sudangrass on more acid soils, and it is free of
the prussic acid hazard associated with sudangrass. Pearl millet can be grazed
when it reaches a height of 1 to 1½ feet, but should be 2 to 4 feet tall when
harvested as hay. Pearl millet is sensitive to close clipping or grazing height;
leaving residual stubble heights of less than 4 to 6 inches can result in
reduced production or death. Dry matter yields in Arkansas forage variety trials
have ranged from 4½ to 5 tons per acre over three cuttings when soil test
recommendations were followed.
III. Small Cereal Grains
In Arkansas, wheat, oats, and rye are the most commonly grown small grains
for forage use. Barley and triticale are also occasionally used. University of
Arkansas research indicates producers should expect dry matter yields of 1.0 to
3.5 tons per acre under proper management. These species can be planted into a
clean-tilled seedbed or overseeded into bermudagrass pastures.
Which Species of Small Grain Should Be Planted?
If supplemental forage is needed early in the spring or late in the fall,
then fall seeded rye is probably the best choice of the small grains because it
grows better at cooler temperatures. Rye is also more tolerant of soil acidity
than the other small-grain options. Fall-seeded oats grow less than rye or wheat
during the cool temperatures of late winter and early spring; generally, oats is
more cold sensitive than other small grains and can be winterkilled during harsh
winters. Only 45 percent of fall-seeded oat production occurs by March 1. The
dry matter production of wheat typically lies between that of rye and oats.
Grain may be harvested from wheat established for supplemental pasture;
however, livestock must be removed when the stem begins to elongate in the
spring (probably about early to mid March in an average year). This practice
typically has little effect on grain production provided adequate fertilizer is
applied and animals are removed in a timely fashion. If a grain crop is not
needed, wheat may continue to provide grazing until bermudagrass breaks its
dormancy. Fall forage production of small grains overseeded into bermuda sods is
usually reduced, relative to clean-tilled plantings, due to competition from the
bermuda.
Rye and ryegrass are sometimes planted as mixtures. This practice has some
advantages; rye provides grazing during the coolest weeks of the growing season,
and ryegrass picks up the slack in production as the production from rye wanes.
Also, the ryegrass helps to improve the quality of the rye forage. Ryegrass is
also mixed with wheat; this combination also makes a supplemental pasture of
excellent quality.
Planting Date
Small grains grown specifically for forage can be planted two weeks earlier
than the same crop planted for grain-only production; however, insect pests such
as Hessian fly may pose more of a problem with early-plantings. The use of fly
resistant wheats may be helpful under these conditions. Small grain supplemental
pastures are normally fall seeded between August 25 and September 30. If the
small grains are overseeded into bermuda sod, some sod suppression is a good
practice; this may include close grazing, haying, herbicide application, and/or
light tillage prior to planting.
If fall plantings are not possible, then spring plantings of oats for hay are
recommended. These plantings should take place as early in the spring as weather
permits. Any of the varieties normally recommended for fall planting in Arkansas
may be used for this purpose. In north Arkansas, the better spring-seeded oat
varieties commonly recommended in south Missouri may be used. Spring seedings of
rye or wheat are not recommended in Arkansas.
Planting Rate
A planting rate of 90 to 120 pounds per acre is recommended if wheat, oats,
or rye are to be planted alone. The higher rates in this range should be used
for spring plantings. The seeding rate should be reduced to 60 to 90 pounds per
acre if 12 to 15 pounds of ryegrass are seeded with the small grain.
Fertilizer Rates
Soil tests should be used to determine the rates of fertilizer to apply. In
the absence of a soil test, one rule of thumb recommendation for a soil of
moderate natural fertility is to apply 60 to 90 pounds of both P205 and K20 per
acre. Apply approximately 50 pounds of nitrogen (about 150 pounds of ammonium
nitrate or 110 pounds of urea) per acre at fall planting time. Excessive
applications of nitrogen in the fall can result in luxury consumption; however,
high forage yields often cannot be sustained without additional applications.
Fifty pounds should be top-dressed again in late February and an additional 50
pounds per acre can be applied in mid-April. This makes a total of 150 pounds of
nitrogen per acre on the crop for a full growing season. Split spring
applications of nitrogen for fall-seeded pastures are particularly important if
a grain harvest is planned subsequent to grazing. Split application should also
be used for spring seedings to reduce the likelihood of nitrate poisoning. Mid
April is a good time to apply the top-dress nitrogen to spring planted oats that
will be used for hay. Fertilization schemes for small grains that have been
overseeded into dormant or semi-dormant (bermuda) sods are similar to those in
clean-tilled seedings, but care must be taken to ensure that nitrogen
fertilization during the establishment of the small grains does not stimulate
substantial growth of the bermudagrass sod. If this situation potentially
exists, nitrogen fertilization should be delayed until after the small grains
are established.
Harvest
Small grains are generally harvested for pasture when they are 6 to 8 inches
tall. Stocking rate should be adequate to both utilize the forage and allow new
leaf growth. Grazing systems can be either rotational or continuous. If these
crops are harvested as hay or silage in the spring, they should be mowed in the
boot to early-heading stages of growth. Some danger exists when cows that are
about to calve or have recently calved graze lush spring small-grain forage.
These cows may suffer from tetany-like symptoms, such as nervousness, muscle
twitching, staggers, convulsions, coma, and frequently, death, but it is not
certain that this case constitutes traditional grass tetany. Substantial
evidence indicates these animals may suffer from calcium, rather than magnesium,
deficiencies. Traditional grass tetany results from animals grazing plants that
are deficient in magnesium. The probability of observing grass tetany increases
when there are low levels of available magnesium in the soil, soil conditions
are extremely wet, and when soils are low in phosphorus, but high in potassium
and nitrogen. Generally, these conditions all limit or inhibit the uptake of
magnesium.
IV. Ryegrass
Pure stands of annual ryegrass are most commonly planted at rates of 20 to 30
pounds per acre and used for supplemental pasture. These rates are reduced by
about 50 percent if ryegrass is seeded in mixtures, most commonly with rye.
Ryegrass is very responsive to nitrogen fertilization, and it will tolerate
moderately acidic soils and moderate flooding. It is not as winter hardy as
orchardgrass or tall fescue and has a fairly high requirement for water. Under
normal weather conditions, most of the forage production from ryegrass will
occur from February or March through May. Ryegrass pastures tolerate close
grazing and are of excellent quality; young stock, finishing beef animals, and
producing dairy cows perform well on them. Ryegrass can also be harvested as hay
or silage; the best combination of tonnage and quality is achieved if the hay is
cut in the flowering stage of growth.
For more information about forage management, contact your county Extension
office or refer to one of our
publications.
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