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BERSEEM CLOVER
Trifolium alexandrinum
Also called: Egyptian clover
Type: summer annual or winter annual legume
Roles: suppress weeds, prevent erosion, green manure,
chopped forage, grazing
Mix with: oats, ryegrass, small grains as nurse crops;
as nurse crop for alfalfa
See charts, p. 66 to 72, for ranking and management summary.
A fast-growing summer annual, berseem clover can produce up to 8 tons
of forage under irrigation. It’s a heavy N producer and the
least winter hardy of all true annual clovers. This makes it an ideal
winterkilled cover before corn or other nitrogen-demanding crops in
Corn Belt rotations. Berseem clover draws down soil N early in its
cycle. Once soil reserves are used up, it can fix 100 to 200 lb. N/A
or more. It establishes well with an oat nurse crop, making it an
excellent cover for small grain>corn>soybean rotations in the
Midwest.
In Iowa, the cultivar BIGBEE compares favorably with alfalfa in
its regrowth following small grain harvest, its feed value and its
tolerance to drought and excess moisture (156).
As a winter annual in California, irrigation usually is needed to
allow berseem to achieve its full potential. Its peak growth period
during the West Coast’s rainy season and its highly efficient
water use compare favorably to alfalfa as a high-producing forage
and green manure.
BENEFITS
Green manure. Berseem clover is the fertility
foundation of agriculture in the Nile Delta, and has nourished soils
in the Mediterranean region for millennia. MULTICUT berseem clover
averaged 280 lb. N/A in a six-year trial in California with six
cuttings per year (162), and
grew faster than BIGBEE in one Iowa report (155).
Berseem is less prone to possible N leaching if grown to maturity
without cutting, when it produces 100 to 125 lb. N/A .Top N fixation
occurs when soils have less than 150 lb. N/A (162).
A single cutting can yield 50 to 100 lb. topgrowth N/A. Berseem’s
dry matter N concentration is about 2.5 percent (162).
Biomass. Berseem clover produced the most biomass
(6,550 lb./A) of five winter annual legumes in a two-year Louisiana
test, and came in second to arrowleaf clover (Trifolium vesiculosum)
in N, accumulating 190 lb. N/A to arrowleaf’s 203 lb. N/A.
Also tested were TIBBEE crimson clover, WOOGENELUP subterraneum
clover and WOODFORD bigflower vetch. All but arrowleaf clover were
able to set seed by May 13 and regrow in the fall, despite the herbicides
used to suppress them in spring and to control weeds during summer
(36).
In Alberta legume trials, berseem clover averaged 3,750 lb. dry
matter/A over three years at a site where hairy vetch and field
peas produced 5,300 and 4,160 lb./A, respectively. With irrigation,
berseem clover topped 19 other legumes at the same site with a mean
yield of 5,500 lb. DM/A.
Smother crop. Planted with oats or annual ryegrass,
berseem clover suppresses weeds well during establishment and regrowth
after oat harvest.
Companion crop. Planted with oat, the two crops
can be harvested together as silage, haylage or hay, depending on
the crop’s development stage. Berseem/oat haylage has very
high feed quality if cut at oats’ boot stage (157).Dry seasons
favor development of an oat grain crop, after which berseem clover
can be cut one, two or three times in the Midwest.
Quick growing. At 60° F, berseem clover will
be ready to cut about 60 days after planting.
Legume nurse crop. Because of its quick germination
(seven days), quick growth and winterkilling tendency, berseem clover
can be used as a nurse crop for alfalfa.
Seed crop. Berseem produces up to 1,000 lb. seed/A
if it is left to mature. Only BIGBEE berseem clover has hard seed
that allows natural self-reseeding, and it reseeds too late for
timely planting of most summer crops (103).
Grazing and forage crop. At 18 to 28 percent protein,
young berseem clover is comparable to or better than crimson clover
or alfalfa as feed. No cases of bloat from grazing berseem clover
have been reported (158, 278).
Forage quality remains acceptable until the onset of seed production.
BIGBEE berseem clover and TIBBEE crimson produce more fall and winter
growth than do other winter annual clovers in the South. BIGBEE
continues producing longer into the spring than other legumes, extending
cuttings into late May or early June in Mississippi (225).
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BERSEEM CLOVER
(Trifolium alexandrinum) |
MANAGEMENT
Establishment
Berseem prefers slightly alkaline loam and silty soils
but grows in all soil types except sands. Soil phosphorus can limit
berseem clover growth. Fertilize with 60 to 100 lb. P2O5/A if soil
tests below 20 ppm (162). Boron
also may limit growth, so test soil to maintain levels (278). Berseem
tolerates saline conditions better than alfalfa and red clover (120).
Use R-type inoculant suitable for berseem clover and crimson clovers.
Broadcast or drill berseem seed alone or with spring grains onto
a firm, well-prepared seedbed or closely cropped sod so that it
is 1/4-inch deep with a light soil covering. To improve seed-soil
contact and to maintain seed-zone moisture, cultipack or roll soil
before and after broadcast seeding (162).
Dry, loose soil will suppress germination.
Recommended seeding rates are 8 to 12 lb./A drilled or 15 to 20
lb./A broadcast. Excessive rates will create an overly thick stand
that prevents tillering and spreading of the root crowns. Montana
trials set the optimum seeding rate at about 8 lb./A drilled in
12-inch rows, with a higher rate in narrower rows where herbicides
are not used to control weeds (442).
Midwest. Seed after April 15 to avoid crop loss
due to a late frost. Berseem frostseeded at 15 lb./A yields well
in the upper Midwest. In southern Michigan, frostseeded berseem
clover produced 1.5 T dry matter/A and 85 lb. N/A (373,
376), but frost risk is significant.
Iowa tests over four years showed that interseeded berseem and
oats averaged 76 percent more dry matter (ranging from 19 to 150
percent) than oats alone. Underseeding berseem clover did not significantly
reduce oat yields in another Iowa study. Seed early- to mid-April
in Iowa (159).
When seeding a mixture, harvest goals affect variety selection
and seeding rates, Iowa researchers have found. If establishment
of an optimum berseem clover stand for green manure
is most important, oat or other small grain crop seeded at about
1 bushel per acre will protect the young clover and help to break
the soil crust. If early forage before green manuring is the goal,
seed a mixture of 4 bu. oats and 15 lb. berseem/A. If biomass
quantity is foremost, use a shortstalked, long-season oat.
If oat grain production is primary, keep oat seeding
rate the same, but select a short-season, tall variety to reduce
the likelihood of berseem clover interfering with grain harvest
(156).
Berseem clover also can be a late-summer crop. Planted in mid-August
in the Corn Belt, it should grow about 15 inches before frost, provide
winter erosion protection and break down quickly in spring to deliver
N from its topgrowth and roots.
You can overseed berseem clover into standing small-grain crops,
a method that has worked well in a series of on-farm tests in Iowa
(155). Plant the berseem as
late as three weeks after the grain crop germinates or after the
tillering stage of winterseeded small grains. Use a heavy seeding
rate to compensate for reduced seed-soil contact. Frostseeding in
late winter into winter wheat has not worked in several attempts
in Pennsylvania (361) and Iowa.
Southeast. Fall planting in mild regions provides
effective weed control as well as N and organic matter for a spring
crop. Seed Aug. 25 to Oct. 15 in Mississippi or up to Dec. 1 in
Florida. For a coolseason grass mixture, plant 12 lb. berseem clover
seed with 10 lb. orchardgrass or 20 lb. annual or perennial ryegrass/A
(225).
West. Berseem does best in California ’s
Central Valley when planted by the first or second week of October.
If planting is delayed until November, seedlings will start more
slowly in the cool of winter (162).
Field Management
Mowing for green manure. Clip whenever plants
are 12 to 15 inches tall and basal shoots begin to grow. This will
be 30 to 60 days after planting, depending on weather, field and
moisture conditions. Mow again every 25 to 30 days to encourage
growth of up to 4 T/A. Keep stubble height at least 3 to 4 inches
tall, because plants regrow from lower stem branches.
To maximize dry matter production, cut as soon as basal bud regrowth
reaches 2 inches (162). At
the latest, clip before early flowering stage or plants will not
regrow. Berseem clover responds best when field traffic is minimized
(156).
Mowed berseem clover left in the field as green manure can hinder
regrowth of the legume from its lower stems. To lessen this problem,
flail or sickle-bar mow then rake or fluff with a tedder at intervals
until regrowth commences.
Remember that berseem clover has a tap root and shallow 6- to 8-inch
feeder root system (156). In
thin plantings or well-drained soils, it can be susceptible to drought,
a trait that could trigger mowing, grazing or killing earlier than
originally planned (186).
Abundant soil N will restrict N fixation by berseem clover, but
moderate amounts up to 150 lb. N/A did not limit annual fixation
in north central California. Researchers explain that berseem clover
draws heavily on soil N during early growth. When soil N was depleted
in this test, berseem began fixing N rapidly until it produced seed
and died (447).
Berseem made its N contribution to soil in the final third of its
cutting cycle—regardless of initial soil N availability—in
all six years of the study. Nitrogen fixation was closely correlated
to a drop in water-use efficiency in the trial. After producing
from 400 to 640 lb. of dry matter per acre-inch of water in the first
four cuttings, production dropped to 300 lb.DM/A -in. for the final
two cuttings (447).
Small grain companion. Underseeded berseem clover
provided about 1.2 T forage dry matter/A after oat harvest in Iowa.
Removing the forage decreases the soil-saving ground cover and N
contribution (159), trading
soil and N benefits for attractive near-term income.
In the Midwest, greenchop an oat/berseem clover mixture when oat
is at the pre-boot stage to avoid berseem clover going to seed early
and, therefore, not producing maximum nitrogen. Oats have high crude
protein at this stage. Monitor carefully during warm periods to
avoid nitrogen toxicity.
A Montana study found that spring plantings of berseem clover will
produce the most legume dry matter and N if clear seeded. If, however,
you wish to maximize total dry matter and protein, seeding
with oats is recommended. The oat nurse crop suppressed weeds well
and increased total dry matter production by 50 to 100 percent regardless
of whether plots were cut two, three or four times (434).
Nodulation: Match Inoculant to Maximize
N
With the help of nitrogen-fixing bacteria, legume
cover crops can supply some or all of the N needed by succeeding
crops. This nitrogen-producing team can’t do the job
right unless you carefully match the correct bacterial inoculant
with your legume cover crop species.
Like other plants, legumes need nitrogen to
grow. They can take it from the soil if enough is present
in forms they can use. Legume roots also seek out specific
strains of soil-dwelling bacteria that can “fix”
nitrogen gas from the air for use by the plant. While many
kinds of bacteria compete for space on legume roots, the root
tissues will only begin this symbiotic N-fixing process when
they encounter a specific species of rhizobium bacteria .Only
particular strains of rhizobia provide optimum N production
for each group of legumes.
When the root hairs find an acceptable bacterial
match, they encircle the bacteria to create a nodule. These
variously shaped lumps on the root surfaces range in size
from a BB pellet to a kernel of corn. Their pinkish interiors
are the visible sign that nitrogen fixation is at work.
Nitrogen gas (N2) from air in the spaces between
soil particles enters the nodule. The bacteria contribute
an enzyme that helps convert the gas to ammonia (NH3). The
plant uses this form of N to make amino acids, the building
blocks for proteins. In return, the host legume supplies the
bacteria with carbohydrates to fuel the N-fixation process.
The rate of N fixation is determined largely
by the genetic potential of the legume species and by the
amount of plant-available N in the soil. Other environmental
factors such as heat and moisture play a big role, as well.
Fueling N fixation is an expensive proposition for the legume
host, which may contribute up to 20 percent of its carbohydrate
production to the root-dwelling bacteria. If the legume can
take up free N from the soil, it won’t put as much energy
into producing nodules and feeding bacteria to fix nitrogen
from the air.
Perennial legumes fix N during any time of active
growth. In annual legumes, N fixation peaks at flowering.
With seed formation, it ceases and the nodules slough from
the roots. Rhizobia return to the soil environment to await
their next encounter with legume roots. These bacteria remain
viable in the soil for three to five years, but often at too
low a level to provide optimum N-fixation when legumes return
to the field.
If legume roots don’t encounter their
ideal bacterial match, they work with the best strains they
can find. They just don’t work as efficiently together
and they produce less N. Inoculating seeds with the correct
strain before planting is inexpensive insurance to make sure
legumes perform up to their genetic potential. Clover inoculum,
for example, costs just a few cents per pound of seed treated,
or more for an enhanced sticker that buffers and feeds the
seedling.
While they are alive, legumes release little
or no nitrogen to the soil. The N in their roots, stalks,
leaves and seeds becomes available when the plants die naturally
or are killed by tillage, mowing or herbicide. This plant
material becomes food for microbes, worms, insects and other
decomposers.
Microorganisms mineralize, or convert, the complex
"organic” forms of nitrogen in the plant material
into inorganic ammonium and nitrate forms, once again making
the N available to plants. How quickly the mineralization
of N occurs is determined by a host of environmental and chemical
factors. These will affect how much of that legume N is available
to the next crop or has the potential to leach from the soil.
For more information about mineralization and
how much you can reduce your N fertilizer rate for crops following
legumes, see How
Much N?.
To get the most from your legume/bacteria combination:
 Choose
appropriate legume species for your climate, soils
and cropping system. Also, consider the amount of N it can
deliver when you will need it.
Match
inoculant to the species of legume you are growing.
See Chart 3B, Planting to determine
the best inoculant to use.
Coat
seed with the inoculant just before planting. Use
milk, weak sugar water or a commercial sticking agent to
help the material stick to the seeds. Use only fresh inoculant
(check the package’s expiration date), and do not
expose packages or inoculated seed to excessive heat or
direct sunlight.
Mix the sticker with non-chlorinated water and
add the inoculant to create a slurry, then thoroughly coat
seeds. Seed should be dry enough to plant within half an hour.
Re-inoculate if you don’t plant the seed
within 48 hours. Mix small quantities in a five-gallon bucket
or tub, either by hand or using a drill equipped with a paint-mixer
attachment. For larger quantities, use special inoculant mixing
hoppers or a cement mixer without baffles.
Gum arabic stickers with sugars and liming agents
boost the chances for optimum nodulation over water-applied
inoculant alone. Pre-inoculated (“rhizo-coated”)
seed weighs about one-third more than raw seed, so increase
seeding rates accordingly.
Check nodulation as the plants approach bloom
stage. Push a spade in the soil about 6 inches below the plant.
Carefully lift the plant and soil, gently exposing roots and
nodules. (Yanking roots from the soil usually strips off nodules).
Wash gently in a bucket of water to see the extent of nodulation.
Slice open nodules. A pink or reddish interior indicates active
N-fixation. Remember, an overabundance of soil nitrogen from
fertilizer, manure or compost can reduce nodulation.
For more information about nodulation, see two
books by Marianne Sarrantonio: Northeast Cover Crop Handbook
(361) and Methodologies
for Screening Soil-Improving Legumes (360). |
Killing
Berseem dies when exposed to temperatures below 20° F for several
days, making winterkill a virtual certainty in Zone 7 and colder.
This eliminates the need for herbicides or mechanical killing after
a cold winter, and hastens delivery of nutrients to the soil.
To kill berseem clover ahead of fall planted crops, wait for it
to die after blooming, use multiple diskings or apply herbicides.
In mild areas, berseem clover grows vigorously through late spring.
BIGBEE berseem clover remained vegetative until early May or later
in an experiment at a northern Mississippi (Zone 7) site. Until
it reaches full bloom, it will require either tillage or a combination
of herbicides and mechanical controls to kill it.
In a northern Mississippi mechanical control study, BIGBEE berseem
clover added the most dry matter after mid-April compared to hairy
vetch, MT. BARKER subterranean clover and TIBBEE crimson clover.
Berseem and hairy vetch remained vegetative until mid-May, but by
early May, berseem clover and crimson had a considerable amount
of stems laying down (105).
Rolling with 4-inch rollers killed less berseem clover than hairy
vetch or crimson when the legumes had more than 10 inches of stem
laying on the ground. Kill rate was more than 80 percent for the
latter two crops, but only 53 percent for berseem clover. Without
an application of atrazine two weeks prior to either flail mowing
or rolling with coulters, the mechanical controls failed to kill
more than 64 percent of the berseem clover until early May, when
flailing achieved 93-percent control. Atrazine alone reduced the
stand by 68 percent in early April, 72 percent in mid-April and
88 percent in early May (105).
Pest Management
Avoid direct seeding small-seeded vegetables into fields where you
have incorporated berseem clover within the past month, due to allelopathic
compounds in the residue. Berseem clover, crimson clover and hairy
vetch residue incorporated directly into the seed zone may suppress
germination and seedling development of onion, carrot and tomato,
based on lab tests (40).
Lygus bugs have been a serious problem in California seed production,
and virus outbreaks can cause serious damage during wet springs
where berseem grows as a winter annual. Where virus is a concern,
use JOE BURTON, a resistant cultivar. BIGBEE is susceptible to crown
rot and other root diseases common to forage legume species (162).
Berseem, like other clovers, shows little resistance to root-knot
nematode (Meloidogyne spp.). It seems to be particularly
favored by rabbits (361).
Crop Systems
Flexible oats booster. In the Corn Belt, berseem
clover seeded with oats helps diversify corn>soybean rotations,
breaks pest cycles and provides some combination of grain and/or
forage harvest, erosion control and N to the following corn crop.
An added benefit is that it requires no tillage or herbicide to
kill it in spring (159). Plant
4 bu. oats with 12 lb. berseem/A.
In a four-year Iowa study, planting berseem clover with oats increased
net profit compared with oats alone. The clover was baled for forage
and the underseeded oats were harvested for grain. Not calculated
in the benefit were the 40 to 60 lb. N/A provided to the following
corn crop or other soil-improvement benefits. The oats/ berseem
mix produced 70 percent more biomass, increased subsequent corn
yields by 10 percent and reduced weed competition compared with
a year of oats alone (159).
Pure berseem clover regrowth averaged 1.2 T dry matter/A, which
can be used as forage or green manure. These options could help
oats become an economically viable crop for Midwest crop/livestock
farms in an era of decreasing government payments for corn and soybeans
(159, 160).
Wheat companion. Berseem was one of six legume
intercrops that improved productivity and profit of wheat and barley
crops in low-N soils under irrigated conditions in northwestern
Mexico. All of the legumes (including common and hairy vetch, crimson
clover, New Zealand and Ladino white clover, and fava beans) provided
multiple benefits without decreasing grain yield of 15 to 60 bu./A
on the heavy clay soil.
Wheat and legumes were planted at normal monoculture rates with
wheat in double rows about 8 inches apart atop 30-inch beds, and
legumes in the furrows. In a second, related experiment, researchers
found they could more than double total wheat productivity (grain
and total dry matter) by interplanting 24-inch strips of berseem
clover or hairy vetch with double rows of wheat 8 inches apart.
Control plots showed wheat planted at a greater density did not
increase yield (350).
Vegetable overseeding. Berseem can be overseeded
into spring vegetables in northern climates where it thrives at
moderate temperatures and moisture. Berseem is well suited to a
“mow and blow” system where strips of green manure are
chopped and transferred to adjacent crop strips as a green manure
and mulch (361).
Boost the N plow-down potential of old pastures or winter-killed
alfalfa by no-tilling or interseeding berseem clover. Or, broadcast
seed then incorporate with light harrowing.
COMPARATIVE NOTES
Berseem clover is:
Not
as drought-tolerant as alfalfa. Some cultivars can tolerate more
soil moisture—but not waterlogging—than alfalfa or
sweet clover
Similar
in seed size to crimson clover
Bee-friendly
because its white or ivory blossoms have no tripping mechanism.
Because
of its short roots, berseem clover does not use phosphorus to
the depth that mature, perennial alfalfa does.
Winterkilled
berseem allows for earlier spring planting than winter-hardy annuals.
As a dead organic mulch, it poses no moisture depletion risk,
but may slow soil warming and drying compared to erosion-prone
bare fallow.
Cultivars. BIGBEE berseem clover was selected
from other traditional cultivars for its cold-tolerance, which is
similar to crimson clover. Some of the strong winter production
tendency found in non-winter hardy berseem clover was sacrificed
to obtain BIGBEE’s winter hardiness (162).
Mature BIGBEE plants hold their seeds well and produce adequate
hard seed for reseeding. Other berseem clover cultivars have less
hard seed and will not dependably reseed (278).
California tests show MULTICUT berseem clover produces 20 to 25
percent more dry matter than BIGBEE. It has greater N-fixing ability,
blooms later, and has a longer growing period than other varieties,
but is not as cold tolerant as BIGBEE (162).
JOE BURTON, developed from MULTICUT, is more cold tolerant.
In California, BIGBEE begins to flower in mid- May, about two weeks
ahead of MULTICUT. MULTICUT grows faster and produces more dry matter
in California conditions, averaging about 1.6 T/A more in a six-year
study. When the five or six cuttings per year were clipped and removed,
MULTICUT was about 6 inches taller at each clipping than other varieties
(447). In Montana tests, BIGBEE
out-yielded MULTICUT in eight of 13 locations (381).
Seed sources. See Seed
Suppliers.
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