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HAIRY VETCH
Vicia villosa
Type: winter annual or summer annual legume
Roles: N source, weed suppressor, topsoil conditioner,
reduce erosion
Mix with: small grains, field peas, bell beans, crimson
clover, buckwheat
See charts, p. 66 to 72, for ranking and management summary.
Few legumes match hairy vetch for spring residue production or nitrogen
contribution. Widely adapted and winter hardy through Hardiness Zone
4 and into Zone 3 (with snow cover), hairy vetch is a top N provider
in temperate and subtropical regions.
The cover grows slowly in fall, but root development continues
over winter. Growth quickens in spring, when hairy vetch becomes
a sprawling vine up to 12 feet long. Field height rarely exceeds
3 feet unless the vetch is supported by another crop. Its abundant,
viney biomass can be a benefit and a challenge. The stand smothers
spring weeds, however, and can help you replace all or most N fertilizer
needs for late-planted crops.
BENEFITS
Nitrogen source. Hairy vetch delivers heavy contributions
of mineralized N (readily available to the following cash crop).
It can provide sufficient N for many vegetable crops, partially
replace N fertilizer for corn or cotton and increase cash crop N
efficiency for higher yield.
In some parts of California and the East in Zone 6, hairy vetch
provides its maximum N by safe corn planting dates. In Zone 7 areas
of the Southeast, the fit is not quite as good, but substantial
N from vetch is often available before corn planting.
Corn planting date comparison trials with cover crops in Maryland
show that planting as late as May 15 (the very end of the
month-long local planting period) optimizes corn yield and profit
from the system. Spring soil moisture was higher under the vetch
or a vetch-rye mixture than under cereal rye or no cover crop. Killed
vetch left on the surface conserved summer moisture for improved
corn production (80, 82,
84, 85,
173, 243).
Even without crediting its soil-improving benefits, hairy vetch
increases N response and produces enough N to pay its way in many
systems. Hairy vetch without fertilizer was the preferred option
for “risk-averse” no-till corn farmers in Georgia, according
to calculations comparing costs, production and markets during the
study. The economic risk comparison included crimson clover, wheat
and winter fallow. Profit was higher, but less predictable, if 50
pounds of N were added to the vetch system (310).
Note: To roughly estimate hairy vetch N contribution
in pounds per acre, cut and weigh fresh vetch top growth from a
4-foot by 4-foot area. Multiply pounds of fresh vetch by 12 to gauge
available N, by 24 to find total N (377).
For a more accurate estimate, see How
Much N?.
Hairy vetch ahead of no-till corn was also the preferred option
for risk averse farmers in a three-year Maryland study that also
included fallow and winter wheat ahead of the corn. The vetch-corn
system maintained its economic advantage when the cost of vetch
was projected at maximum historic levels, fertilizer N price was
decreased, and the herbicide cost to control future volunteer vetch
was factored in (173). In a
related study on the Maryland Coastal Plain, hairy vetch proved
to be the most profitable fall-planted, spring desiccated legume
ahead of no-till corn, compared with Austrian winter peas and crimson
clover (243).
In Wisconsin’s shorter growing season, hairy vetch planted
after oat harvest provided a gross margin of $153/A in an oat/legume/corn
rotation (1995 data). Profit was similar to using 160 lb. N/A in
continuous corn, but with savings on fertilizer and corn rootworm
insecticide (400).
Hairy vetch provides yield improvements beyond those attributable
to N alone. These may be due to mulching effects, soil structure
improvements leading to better moisture retention and crop root
development, soil biological activity and/or enhanced insect populations
just below and just above the soil surface.
Soil conditioner. Hairy vetch can improve root
zone water recharge over winter by reducing runoff and allowing
more water to penetrate the soil profile through macropores created
by the crop residue (143).
Adding grasses that take up a lot of water can reduce the amount
of infiltration and reduce the risk of leaching in soils with excess
nutrients. Hairy vetch, especially an oats/hairy vetch mix, decreased
surface ponding and soil crusting in loam and sandy loam soils.
Researchers attribute this to dual cover crop benefits: their ability
to enhance the stability of soil aggregates (particles), and to
decrease the likelihood that the aggregates will disintegrate in
water (143).
Hairy vetch improves topsoil tilth, creating a loose and friable
soil structure. Vetch doesn’t build up long-term soil organic
matter due to its tendency to break down completely. Vetch is a
succulent crop, with a relatively “low” carbon to nitrogen
ratio. Its C:N ratio ranges from 8:1 to 15:1, expressed as parts
of C for each part of N. Rye C:N ratios range from 25:1 to 55:1,
showing why it persists much longer under similar conditions than
does vetch. Residue with a C:N ratio of 25:1 or more tends to immobilize
N. For more information, see How
Much N?, and the rest of that section, Building
Soil Fertility and Tilth with Cover Crops.
Early weed suppression. The vigorous spring growth
of fall-seeded hairy vetch out-competes weeds, filling in where
germination may be a bit spotty. Residue from killed hairy vetch
has a weak allelopathic effect, but it smothers early weeds mostly
by shading the soil. Its effectiveness wanes as it decomposes, falling
off significantly after about three or four weeks. For optimal weed
control with a hairy vetch mulch, select crops that form a quick
canopy to compensate for the thinning mulch or use high-residue
cultivators made to handle it.
Mixing rye and crimson clover with hairy vetch (seeding rates of
30, 10, and 20 lb./A, respectively) extends weed control to five
or six weeks, about the same as an all-rye mulch. Even better, the
mix provides a legume N boost, protects soil in fall and winter
better than legumes, yet avoids the potential crop-suppressing effect
of a pure rye mulch on some vegetables.
Good with grains. For greater control of winter
annual weeds and longer-lasting residue, mix hairy vetch with winter
cereal grains such as rye, wheat or oats.
Growing grain in a mixture with a legume not only lowers the overall
C:N ratio of the combined residue compared with that of the grain,
it may actually lower the C:N ratio of the small grain residue as
well. This internal change causes the grain residue to break down
faster, while accumulating the same levels of N as it did in a monoculture
(344).
Moisture-thrifty. Hairy vetch is more drought
tolerant than other vetches. It needs a bit of moisture to establish
in fall and to resume vegetative growth in spring, but relatively
little over winter when above-ground growth is minimal.
Phosphorus scavenger. Hairy vetch showed higher
plant phosphorus (P) concentrations than crimson clover, red clover
or a crimson/ryegrass mixture in a Texas trial. Soil under hairy
vetch also had the lowest level of P remaining after growers applied
high amounts of poultry litter prior to vegetable crops (121).
Fits many systems. Hairy vetch is ideal ahead
of early-summer planted or transplanted crops, providing N and an
organic mulch. Some Zone 5 Midwestern farmers with access to low-cost
seed plant vetch after winter grain harvest in midsummer to produce
whatever N it can until it winterkills or survives to regrow in
spring.
Widely adapted. Its high N production, vigorous
growth, tolerance of diverse soil conditions, low fertility need
and winter hardiness make hairy vetch the most widely used of winter
annual legumes.
|
HAIRY VETCH
(Vicia villosa) |
MANAGEMENT
Establishment & Fieldwork
Hairy vetch can be no-tilled, drilled into a prepared seedbed or
broadcast. Dry conditions often reduce germination of hairy vetch.
Drill seed at 15 to 20 lb./A, broadcast 25 to 30 lb./A. Select a
higher rate if you are seeding in spring, late in the fall, or into
a weedy or sloped field. Irrigation will help germination, particularly
if broadcast seeded.
Plant vetch 30 to 45 days before killing frost for winter annual
management; in early spring for summer growth; or in July if you
want to kill or incorporate it in fall or for a winter-killed mulch.
Hairy vetch has a relatively high P and K requirement and, like
all legumes, needs sufficient sulfur and prefers a pH between 6.0
and 7.0. However, it can survive through a broad pH range of 5.0
to 7.5 (120).
An Illinois farmer successfully no-tills hairy vetch in late August
at 22 lb./A into closely mowed stands of fescue on former Conservation
Reserve Program land (417).Using
a herbicide to kill the fescue is cheaper than mowing, but it must
be done about a month later when the grass is actively growing for
the chemical to be effective. Vetch also can be no-tilled into soybean
or corn stubble (50, 80).
In Minnesota, vetch can be interseeded into sunflower or corn at
last cultivation. Sunflower should have at least 4 expanded leaves
or yield will be reduced (221,
222).
Farmers in the Northeast’s warmer areas plant vetch by mid-September
to net 100 lb. available N/A by mid-May. Sown mid-August, an oats/hairy
vetch mix can provide heavy residue (180).
Rye/hairy vetch mixtures mingle and moderate the effects of each
crop. The result is a “hybrid” cover crop that takes
up and holds excess soil nitrate, fixes N, stops erosion, smothers
weeds in spring and on into summer if not incorporated, contributes
a moderate amount of N over a longer period than vetch alone, and
offsets the N limiting effects of rye (81,
83, 84,
86, 377).
Seed vetch/rye mixtures, at 15-25 lb. hairy vetch with 40-70 lb.
rye/A (81, 361).
Overseeding (40 lb./A) at leaf-yellowing into soybeans can work
if adequate rainfall and soil moisture are available prior to the
onset of freezing weather. Overseeding into ripening corn (40 lb./A)
or seeding at layby has not worked as consistently. Late overseeding
into vegetables is possible, but remember that hairy vetch will
not stand heavy traffic (361).
Cover Crop Roller Design Holds Promise
For No-Tillers
However, timing of control and planting in a single pass
could limit adoption; hope lies in breeding cover crops that
flower in time for traditional planting window.
THE POSSIBILITY of using rollers to reduce herbicide
use isn’t new, but advances are being made to improve
the machines in ways that could make them practical for controlling
no-till cover crops.
Cover crop rolling is gaining visibility and
credibility in tests by eight university/farmer research teams
across the country. The test rollers were designed and contributed
by The Rodale Institute (TRI), a Pennsylvania -based organization
focused on organic agricultural research and education. The
control achieved with the roller is comparable to a roller
combined with a glyphosate application, according to TRI.
The Rodale crop rollers were delivered to state
and federal cooperative research teams in Virginia, Michigan,
Mississippi, North Dakota, Pennsylvania, Georgia, California
and Iowa in Spring, 2005. Funding for the program comes from
grants and contributions from the Natural Resources Conservation
Service and private donors. I&J Manufacturing in Gap,
Pa., fabricated the models distributed to the research teams.
“The requirement is that each research
leader partners with a farmer cooperator to adapt the rollers
to local conditions and cover cropping systems,” explains
Jeff Moyer, TRI’s farm manager. “Our goal is to
gain more knowledge about the soil building and weed management
effects of cover crops while reducing the need for herbicides,”
he says.
Farmer Built. Moyer designed
and built the first front-mounted TRI roller prototype in
2002 in conjunction with Pennsylvania farmer John Brubaker,
whose land abuts the TRI property. The original 10-foot, 6-inch
roller width is equal to 4 rows on 30-inch spacing, with a
3-inch overlap on each end. The original design has already
been modified to include a 15-foot, 6-inch model suitable
for use with a 6- row planter on 30-inch rows. It can be adapted
to fit a 4-row planter on 38-inch rows, and a 5- foot version
for 2-row vegetable planters.
“We realize that 6-row equipment is small
by today’s standards, and work is under way on a system
that mounts one section of the roller in front of the tractor
with the remainder mounted on the planter ahead of the row
units. This design will allow as wide a roller system as a
farmer needs,” Moyer says.
Chevron Pattern. The chevron
pattern on the face of the roller came about after the designers
realized that mounting the roller blades in a straight line
would cause excessive bouncing, while just curving the blades
in a screw pattern would act like an auger and create a pulling
effect. “If you were driving up a hill that might be
fine, but we don’t need help pulling our tractors down
the steep slopes we farm. The chevron pattern neutralizes
any forces that might pull the tractor in either direction,”
Moyer explains. It overcomes both the bounce of straight-line
blades and the auguring effect of corkscrew blades.
“In addition, with the twisted blade design,
only a very small portion of the blade touches the ground
at any one time as it turns, so the full pressure of the roller
is applied 1 inch at a time. This roller design works better
than anything we’ve ever used,” he adds.
Prior to settling on the TRI prototype, Moyer
and Brubaker studied stalk choppers with nine rolling drums
arranged in two parallel rows. This design required 18 bearings
and provided lots of places for green plant material to bunch
up. The TRI ground-driven roller has a single cylinder and
two offset bearings inset 3 inches on either side and fronted
with a shield. The blades are welded onto the 16-inch-diameter
drum, but replacement blades can be purchased from the manufacturer
and bolted on as needed. The 10-foot, 6-inch roller weighs
1,200 pounds empty and 2,000 pounds if filled with water.
Front Mount Benefits. The biggest
advantage of the front-mounted roller is that the operator
can roll the cover crop and no-till the cash crop in a single
field pass, Moyer explains. In TRI trials, simultaneous rolling
and no-till planting eliminated seven of the eight field passes
usually necessary with conventional organic corn production,
including plowing, discing, packing, planting, two rotary
hoe passes and two cultivations.
Rolling the field and no-tilling in one pass
also eliminates the problem of creating a thick green cover
crop mat that makes it difficult to see a row marker line
on a second pass for planting.
Also, planting in a second pass in the opposite
direction from which the cover crop was rolled makes getting
uniform seeding depth and spacing more difficult because the
planter tends to stand the plant material back up. “Think
of it as combing the hair on your dog backwards,” Moyer
says.
“Another disadvantage of rear-mounted
machines like stalk choppers is that the tractor tire is the
first thing touching the cover crop. If the soil is even a
little spongy, the cover crop will be pushed into the tire
tracks and because the roller is running flat, it can’t
crimp the depressed plant material. A week later the plants
missed by the roller will be back up and growing again.”
Crop Versatility. The TRI roller
concept has been tested in a wide range of winter annual cover
crops, including cereal rye, hairy vetch, wheat, triticale,
oats, buckwheat, clover, winter peas and other species. Timing
is the key to success, Moyer emphasizes, and a lot of farmers
don’t have the patience to make it work right.
“The bottom line is that winter annuals
want to die anyway, but if you time it wrong, they’re
hard to kill,” he says. “If you try to roll a
winter annual before it has flowered—before it has physiologically
reproduced—the plant will try to stand up again and
complete the job of reproduction, the most important stage
of its life cycle. But, if you roll it after it has flowered,
it will dry up and die.”
At least a 50 percent, and preferably a 75 to
100 percent bloom, is recommended before rolling. Moyer hopes
to see plant breeders recognize the need to develop cover
crop varieties with blooming characteristics that coincide
with preferred crop planting windows.
“We really like to use hairy vetch on
our farm, for example, because it’s a great source of
nitrogen and is a very suitable crop to plant corn into. The
roller crimps the stem of the hairy vetch every 7 inches,
closing the plant’s vascular system and ensuring its
demise.
“The problem is we would like it to flower
a couple weeks earlier to fit our growing season. It’s
hard for farmers to understand when it’s planting time
and we’re telling them to wait a couple more weeks for
their cover crop to flower,” he says.
“We need to identify the characteristics
we want in cover crops and encourage plant breeders to focus
on some of those. It should be a relatively easy task to get
an annual crop to mature a couple weeks earlier, compared
to some of the breakthrough plant breeding we’ve seen
recently,” Moyer says.
For More Information. Updates
on roller research, more farmer stories and plans for the
TRI no-till cover crop roller can be accessed at www.newfarm.org/depts/no-till.
To ask questions of The Rodale Institute, e-mail to info@rodaleinst.org.
See also “Where can I find information
about the mechanical roller-crimper used in no-till production?”
http://attra
.ncat.org/calendar/question.php/2006/05/08/p2221.
To contact the manufacturer of commercially
available cover crop rollers, visit www.croproller.com.
Editor’s Note: PURPLE
BOUNTY, a new, earlier variety of hairy vetch, was released
in 2006 by the USDA -Agricultural Research Service, Beltsville,
MD in collaboration with the Rodale Institute, Pennsylvania
State University and Cornell University.
—Ron Ross. Adapted with permission from
www.no-tillfarmer.com |
Killing
Your mode of killing hairy vetch and managing residue will depend
on which of its benefits are most important to you. Incorporation
of hairy vetch vegetation favors first-year N contribution, but
takes significant energy and labor. Keeping vetch residue on the
surface favors weed suppression, moisture retention, and insect
habitat, but may reduce N contribution. However, even in no-till
systems, hairy vetch consistently provides very large N input (replacing
up to 100 lb. N/A).
In spring, hairy vetch continues to add N through its “seed
set” stage after blooming. Biomass and N increase until maturity,
giving either greater benefit or a dilemma, depending on your ability
to deal with vines that become more sprawling and matted as they
mature.
Mulch-retaining options include strip-tilling or strip chemical
desiccation (leaving vetch untreated between the strips), mechanical
killing (rotary mowing, flailing, cutting, sub-soil shearing with
an undercutter, or chopping/flattening with a roller/crimper) or
broadcast herbicide application.
No-till corn into killed vetch. The best time
for no-till corn planting into hairy vetch varies with local rainfall
patterns, soil type, desired N contribution, season length and vetch
maturity.
In southern Illinois, hairy vetch no-tilled into
fescue provided 40 to 180 lb. N/A per year over 15 years for one
researcher/farmer. He used herbicide to kill the vetch about two
weeks before the area’s traditional mid-May corn planting
date. The 14-day interval was critical to rid the field of prairie
voles, present due to the field’s thick fescue thatch.
He kills the vetch when it is in its pre-bloom or bloom stage,
nearing its peak N-accumulation capacity. Further delay would risk
loss of soil moisture in the dry period customary there in early
June. When the no-tilled vetch was left to grow one season until
seed set, it produced 6 tons of dry matter and contributed a potentially
polluting 385 lb. N/A (417).
This high dose of N must be managed carefully during the next year
to prevent leaching or surface runoff of nitrates.
A series of trials in Maryland showed a different mix of conditions.
Corn planting in late-April is common there, but early killing of
vetch to plant corn then had the surprising effect of decreasing
soil moisture and corn yield, as well as predictably lowering N
contribution. The earlier planted corn had less moisture-conserving
residue. Late April or early May kill dates, with corn no-tilled
10 days later, consistently resulted in higher corn yields than
earlier kill dates (82, 83,
84, 85).
With hairy vetch and a vetch/rye mixture, summer soil water conservation
by the cover crop residue had a greater impact than spring moisture
depletion by the growing cover crop in determining corn yield (84,
85).
Results in the other trials, which also included a pure rye cover,
demonstrated the management flexibility of a legume/grain mix. Early
killed rye protects the soil as it conserves water and N, while
vetch killed late can meet a large part of the N requirement for
corn. The vetch/rye mixture can conserve N and soil moisture while
fixing N for the subsequent crop. The vetch and vetch/rye mixture
accumulated N at 130 to 180 lb./A. The mixture contained as much
N or more than vetch alone (85,
86).
In an Ohio trial, corn no-tilled into hairy vetch
at mid-bloom in May received better early season weed control from
vetch mulch than corn seeded into vetch killed earlier. The late
planting date decreased yield, however (189),
requiring calculation to determine if lower costs for tillage, weed
control, and N outweigh the yield loss.
Once vetch reaches about 50% bloom, it is easily killed by any
mechanical treatment. To mow-kill for mulch, rye grown with hairy
vetch improves cutting by holding the vetch off the ground to allow
more complete severing of stems from roots. Rye also increases the
density of residue covering the vetch stubble to prevent regrowth.
Much quicker and more energy-efficient than mowing is use of a
modified Buffalo rolling stalk chopper, an implement designed to
shatter standing corn stubble. The chopper’s rolling blades
break over, crimp and cut crop stems at ground level, and handle
thick residue of hairy vetch at 8 to 10 mph (169).
No-till vegetable transplanting. Vetch that is
suppressed or killed without disturbing the soil maintains moisture
well for transplanted vegetables. No-till innovator Steve Groff
of Lancaster County, PA,, uses the rolling stalk chopper to create
a killed organic mulch. His favorite mix is 25 lb. hairy vetch,
30 lb. rye and 10 lb. crimson clover/A.
No-till, delayed kill. Farmers and researchers
are increasingly using a roller/crimper to kill hairy vetch and
other cover crops (11). Jeff
Moyer and others at the Rodale Institute in Kutztown, Pa ., roll
hairy vetch and other cover crops in late May or early June (at
about 50% flower). The modified roller is front-mounted, and corn
is no-tilled on the same pass (303).
See Cover Crop Roller Design Holds Promise For
No-Tillers.
Also useful in killing hairy vetch on raised beds for vegetables
and cotton is the improved prototype of an undercutter that leaves
severed residue virtually undisturbed on the surface (96).
The undercutter tool includes a flat roller attachment, which, by
itself, usually provides only partial suppression unless used after
flowering.
Herbicides will kill vetch in three to 30 days, depending on the
material used, rate, growth stage and weather conditions.
Vetch incorporation. As a rule, to gauge the optimum
hairy vetch kill date, credit vetch with adding two to three pounds
of N per acre per sunny day after full spring growth begins. Usually,
N contribution will be maximized by early bloom (10-25 percent)
stage.
Cutting hairy vetch close to the ground at full bloom stage usually
will kill it. However, waiting this long means it will have maximum
top growth, and the tangled mass of mature vetch can overwhelm many
smaller mowers or disks. Flail mowing before tillage helps, but
that is a time and horsepower intensive process. Sickle-bar mowers
should only be used when the vetch is well supported by a cereal
companion crop and the material is dry (422).
Management Cautions
About 10 to 20 percent of vetch seed is “hard” seed
that lays ungerminated in the soil for one or more seasons. This
can cause a weed problem, especially in winter grains. In wheat,
a variety of herbicides are available, depending on crop growth
stage. After a corn crop that can utilize the vetch-produced N,
you could establish a hay or pasture crop for several years.
Don’t plant hairy vetch with a winter grain if you want to
harvest grain for feed or sale. Production is difficult because
vetch vines will pull down all but the strongest stalks. Grain contamination
also is likely if the vetch goes to seed before grain harvest. Vetch
seed is about the same size as wheat and barley kernels, making
it hard and expensive to separate during seed cleaning (361).
Grain price can be markedly reduced by only a few vetch seeds per
bushel.
A severe freeze with temperatures less than 5° F may kill hairy
vetch if there is no snow cover, reducing or eliminating the stand
and most of its N value. If winterkill is possible in your area,
planting vetch with a hardy grain such as rye ensures spring soil
protection.
Pest Management
In legume comparison trials, hairy vetch usually hosts
numerous small insects and soil organisms (206).
Many are beneficial to crop production, (see below) but others are
pests. Soybean cyst nematode (Heterodera glycines) and
root-knot nematode (Meliodogyne spp.) sometimes increase
under hairy vetch. If you suspect that a field has nematodes, carefully
sample the soil after hairy vetch. If the pests reach an economic
threshold, plant nematode-resistant crops and consider using another
cover crop.
Other pests include cutworms (361)
and southern corn rootworm (67),
which can be problems in no-till corn, tarnished plant bug, noted
in coastal Massachusetts (56),
which readily disperses to other crops, and two-spotted spider mites
in Oregon pear orchards (142).
Leaving unmowed remnant strips can lessen movement of disruptive
pests while still allowing you to kill most of the cover crop (56).
Prominent among beneficial predators associated with hairy vetch
are lady beetles, seven-spotted ladybeetles (56)
and bigeyed bugs (Geocaris spp.). Vetch harbors pea aphids
(Acyrthosiphon pisum) and blue alfalfa aphids (Acyrthosiphon
kondoi) that do not attack pecans but provide a food source
for aphid-eating insects that can disperse into pecans (58).
Similarly, hairy vetch blossoms harbor flower thrips (Frankliniella
spp.), which in turn attract important thrip predators such
as insidious flower bugs (Orius insidiosus) and minute
pirate bugs (Orius tristicolor).
Two insects may reduce hairy vetch seed yield in heavy infestations:
the vetch weevil or vetch bruchid. Rotate crops to alleviate buildup
of these pests (361).
Vetch Beats Plastic
BELTSVILLE, MD.—Killed cover crop mulches
can deliver multiple benefits for no-till vegetable crops
(1, 2,
3, 4).
The system can provide its own N, quell erosion and leaching,
and displace herbicides. It’s also more profitable than
conventional commercial production using black plastic mulch.
A budget analysis showed it also should be the first choice
of “risk averse” farmers, who prefer certain although
more modest profit over higher average profit that is less
certain (224).
The key to the economic certainty of a successful
hairy vetch planting is its low cost compared with the black
plastic purchase, installation and removal.
From refining his own research and on-farm tests
in the mid-Atlantic region for several years, Aref Abdul-Baki,
formerly of the USDA ’s Beltsville (Md.) Agricultural
Research Center, outlines his approach:
 Prepare
beds—just as you would for planting tomatoes—at
your prime time to seed hairy vetch.
Drill
hairy vetch at 40 lb./A, and expect about 4 inches of top
growth before dormancy, which stretches from mid- December
to mid-March in Maryland.
After
two months’ spring growth, flail mow or use other
mechanical means to suppress the hairy vetch. Be ready to
remow or use herbicides to clean up trouble spots where
hairy vetch regrows or weeds appear.
Transplant
seedlings using a minimum tillage planter able to cut through
the mulch and firm soil around the plants.
The hairy vetch mulch suppresses early season
weeds. It improves tomato health by preventing soil splashing
onto the plants, and keeps tomatoes from soil contact, improving
quality. Hairy vetch-mulched plants may need more water. Their
growth is more vigorous and may yield up to 20 percent more
than those on plastic. Completing harvest by mid- September
allows the field to be immediately reseeded to hairy vetch.
Waiting for vetch to bloom in spring before killing it and
the tight fall turnaround may make this system less useful
in areas with a shorter growing season than this Zone 7, mid-Atlantic
site.
Abdul-Baki rotates season-long cash crops of
tomatoes, peppers and cantaloupe through the same plot between
fall hairy vetch seedings. He shallow plows the third year
after cantaloupe harvest and seeds hairy vetch for flat-field
crops of sweet corn or snap beans the following summer.
He suggests seeding rye (40 lb./A) with the
vetch for greater biomass and longer-lasting mulch. Adding
10-12 lb./A of crimson clover will aid in weed suppression
and N value. Rolling the covers before planting provides longer-lasting
residue than does mowing them. Some weeds, particularly perennial
or winter annual weeds, can still escape this mixture, and
may require additional management (4). |
CROP SYSTEMS
In no-till systems, killed hairy vetch creates a short-term but
effective spring/summer mulch, especially for transplants. The mulch
retains moisture, allowing plants to use mineralized nutrients better
than unmulched fields. The management challenge is that the mulch
also lowers soil temperature, which may delay early season growth
(361). One option is to capitalize
on high quality, low-cost tomatoes that capture the late-season
market premiums. See Vetch Beats Plastic.
How you kill hairy vetch influences its ability to suppress weeds.
Durability and effectiveness as a lightblocking mulch are greatest
where the stalks are left whole. Hairy vetch severed at the roots
or sickle-bar mowed lasts longer and blocks more light than flailed
vetch, preventing more weed seeds from germinating (96,
411).
Note: An unmowed rye/hairy vetch mix sustained
a population of aphid-eating predators that was six times that of
the unmowed volunteer weeds and 87 times that of mown grass and
weeds (57).
Southern farmers can use an overwintering hairy vetch crop in continuous
no-till cotton. Vetch mixed with rye has provided similar or even
increased yields compared with systems that include conventional
tillage, winter fallow weed cover and up to 60 pounds of N fertilizer
per acre. Typically, the cover crops are no-till drilled after shredding
cotton stalks in late October. Covers are spray killed in mid-April
ahead of cotton planting in May. With the relatively late fall planting,
hairy vetch delivers only part of its potential N in this system.
It adds cost, but supplies erosion control and long-term soil improvement
(35).
Cotton yields following incorporated hairy vetch were perennial
winners for 35 years at a northwestern Louisiana USDA site. Soil
organic matter improvement and erosion control were additional benefits
(276).
Other Options
Spring sowing is possible, but less desirable than fall establishment
because it yields significantly less biomass than overwintering
stands. Hot weather causes plants to languish.
airy vetch makes only fair grazing—livestock do not relish
it.
Harvesting seed. Plant hairy vetch with grains
if you intend to harvest the vetch for seed. Use a moderate seeding
rate of 10-20 lb./A to keep the stand from getting too rank. Vetch
seed pods will grow above the twining vetch vines and use the grain
as a trellis, allowing you to run the cutter bar higher to reduce
plugging of the combine. Direct combine at mid-bloom to minimize
shattering, or swath up to a week later. Seed is viable for at least
five years if properly stored (361).
If you want to save dollars by growing your own seed, be aware
that the mature pods shatter easily, increasing the risk of volunteer
weeds. To keep vetch with its nurse crop, harvest vetch with a winter
cereal and keep seed co-mingled for planting. Check the mix carefully
for weed seeds.
COMPARATIVE NOTES
Hairy vetch is better adapted to sandy soils than crimson clover
(344), but is less heat-tolerant
than LANA woollypod vetch. See Woollypod
Vetch.
Cultivars. MADISON—developed in Nebraska
— tolerates cold better than other varieties. Hairy vetches
produced in Oregon and California tend to be heat tolerant. This
has resulted in two apparent types, both usually sold as “common”
or “variety not stated” (VNS). One has noticeably hairy,
bluish-green foliage with bluish flowers and is more cold-tolerant.
The other type has smoother, deep-green foliage and pink to violet
flowers.
A closely related species—LANA woollypod vetch (Vicia
dasycarpa)—was developed in Oregon and is less cold tolerant
than Vicia villosa. Trials in southeastern Pennsylvania
with many accessions of hairy vetch showed big flower vetch (Vicia
grandiflora, cv WOODFORD) was the only vetch species hardier
than hairy vetch. EARLY COVER hairy vetch is about 10 days earlier
than regular common seed. PURPLE BOUNTY, released in 2006, is a
few days earlier and provides more biomass and better ground cover
than EARLY COVER.
Seed sources. See Seed
Suppliers.
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