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BUCKWHEAT
Fagopyrum esculentum
Type: summer or cool-season annual broadleaf grain
Roles: quick soil cover, weed suppressor, nectar
for pollinators and beneficial insects, topsoil loosener, rejuvenator
for low-fertility soils
Mix with: sorghum-sudangrass hybrids, sunn hemp
See charts, pp. 66 to 72, for ranking and management summary.
Buckwheat is the speedy short-season cover crop. It establishes, blooms
and reaches maturity in just 70 to 90 days and its residue breaks
down quickly. Buckwheat suppresses weeds and attracts beneficial insects
and pollinators with its abundant blossoms. It is easy to kill, and
reportedly extracts soil phosphorus from soil better than most grain-type
cover crops.
Buckwheat thrives in cool, moist conditions but it is not frost
tolerant. Even in the South, it is not grown as a winter annual.
Buckwheat is not particularly drought tolerant, and readily wilts
under hot, dry conditions. Its short growing season may allow it
to avoid droughts, however.
BENEFITS
Quick cover. Few cover crops establish as rapidly
and as easily as buckwheat. Its rounded pyramid- shaped seeds germinate
in just three to five days. Leaves up to 3 inches wide can develop
within two weeks to create a relatively dense, soil shading canopy.
Buckwheat typically produces only 2 to 3 tons of dry matter per
acre, but it does so quickly—in just six to eight weeks (257).
Buckwheat residue also decomposes quickly, releasing nutrients to
the next crop.
Weed suppressor. Buckwheat’s strong weed suppressing
ability makes it ideal for smothering warm-season annual weeds.
It’s also planted after intensive, weed-weakening tillage
to crowd out perennials. A mix of tillage and successive dense seedings
of buckwheat can effectively suppress Canada thistle, sowthistle,
creeping jenny, leafy spurge, Russian knapweed and perennial peppergrass
(257). While living buckwheat
may have an allelopathic weed-suppressing effect (351),
its primary impact on weeds is through shading and competition.
Phosphorus scavenger. Buckwheat takes up phosphorus
and some minor nutrients (possibly including calcium) that are otherwise
unavailable to crops, then releasing these nutrients to later crops
as the residue breaks down. The roots of the plants produce mild
acids that release nutrients from the soil. These acids also activate
slow-releasing organic fertilizers, such as rock phosphate. Buckwheat’s
dense, fibrous roots cluster in the top 10 inches of soil, providing
an extensive root surface area for nutrient uptake.
Thrives in poor soils. Buckwheat performs better
than cereal grains on low-fertility soils and soils with high levels
of decaying organic matter. That’s why it was often the first
crop planted on cleared land during the settlement of woodland areas
and is still a good first crop for rejuvenating over-farmed soils.
However, buckwheat does not do well in compacted, droughty or excessively
wet soils.
Quick regrowth. Buckwheat will regrow after mowing
if cut before it reaches 25 percent bloom. It also can be lightly
tilled after the midpoint of its long flowering period to reseed
a second crop. Some growers bring new land into production by raising
three successive buckwheat crops this way.
Soil conditioner. Buckwheat’s abundant,
fine roots leave topsoil loose and friable after only minimal tillage,
making it a great mid-summer soil conditioner preceding fall crops
in temperate areas.
Nectar source. Buckwheat’s shallow white
blossoms attract beneficial insects that attack or parasitize aphids,
mites and other pests. These beneficials include hover flies (Syrphidae),
predatory wasps, minute pirate bugs, insidious flower bugs, tachinid
flies and lady beetles. Flowering may start within three weeks of
planting and continue for up to 10 weeks.
Nurse crop. Due to its quick, aggressive start,
buckwheat is rarely used as a nurse crop, although it can be used
anytime you want quick cover. It is sometimes used to protect late-fall
plantings of slow-starting, winter-hardy legumes wherever freezing
temperatures are sure to kill the buckwheat.
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BUCKWHEAT
(Fagopyrum esculentum) |
MANAGEMENT
Buckwheat prefers light to medium, well-drained soils—sandy
loams, loams, and silt loams. It performs poorly on heavy, wet soils
or soils with high levels of limestone. Buckwheat grows best in
cool, moist conditions, but is not frost-tolerant. It is also not
drought tolerant. Extreme afternoon heat will cause wilting, but
plants bounce back overnight.
Establishment
Plant buckwheat after all danger of frost. In untilled, minimally
tilled or clean-tilled soils, drill 50 to 60 lb./A at 1/2 to 11/2
inches deep in 6 to 8 inch rows. Use heavier rates for quicker canopy
development. For a fast smother crop, broadcast up to 96 lb./A (2
bu./A) onto a firm seedbed and incorporate with a harrow, tine
weeder, disk or field cultivator. Overall vigor is usually better
in drilled seedings. As a nurse-crop for slow growing, winter annual
legumes planted in late summer or fall, seed at one-quarter to one-third
of the normal rate.
Buckwheat compensates for lower seeding rates by developing more
branches per plant and more seeds per blossom. However, skimping
too much on seed makes stands more vulnerable to early weed competition
until the canopy fills in. Using cleaned, bin-run or even birdseed-grade
seed can lower establishment costs, but increases the risk of weeds.
As denser stands mature, stalks become spindly and are more likely
to lodge from wind or heavy rain.
Rotations
Buckwheat is used most commonly as a mid-summer cover crop to suppress
weeds and replace bare fallow. In the Northeast and Midwest, it
is often planted after harvest of early vegetable crops, then followed
by a fall vegetable, winter grain, or cool-season cover crop. Planted
later, winterkilled residue provides decent soil cover and is easy
to no-till into. In many areas, it can be planted following harvest
of winter wheat or canola.
In parts of California, buckwheat grows and flowers between the
killing of winter annual legume cover crops in spring and their
re-establishment in fall. Some California vineyard managers seed
3-foot strips of buckwheat in row middles, alternating it and another
summer cover crop, such as sorghum-sudangrass.
Buckwheat is sensitive to herbicide residues from previous crops,
especially in no-till seedbeds. Residue from trifluralin and from
triazine and sulfonylurea herbicides have damaged or killed buckwheat
seedlings (79). When in doubt,
sow and water a small test plot of the fast germinating seed to
detect stunting or mortality.
Pest Management
Few pests or diseases bother buckwheat. Its most serious weed competitors
are often small grains from preceding crops, which only add to the
cover crop biomass. Other grass weeds can be a problem, especially
in thin stands. Weeds also can increase after seed set and leaf
drop. Diseases include a leaf spot caused by the fungus Ramularia
and Rhizoctonia root rot.
Other Options
Plant buckwheat as an emergency cover crop to protect soil and suppress
weeds when your main crop fails or cannot be planted in time due
to unfavorable conditions.
To assure its role as habitat for beneficial insects, allow buckwheat
to flower for at least 20 days—the time needed for minute
pirate bugs to produce another generation.
Buckwheat can be double cropped for grain after harvesting early
crops if planted by mid-July in northern states or by early August
in the South. It requires a two-month period of relatively cool,
moist conditions to prevent blasting of the blossoms. There is modest
demand for organic and specially raised food-grade buckwheat in
domestic and overseas markets. Exporters usually specify variety,
so investigate before planting buckwheat for grain.
Management Cautions
Buckwheat can become a weed. Kill within 7 to 10 days after flowering
begins, before the first seeds begin to harden and turn brown. Earliest
maturing seed can shatter before plants finish blooming. Some seed
may overwinter in milder regions.
Buckwheat can harbor insect pests including Lygus bugs, tarnished
plant bugs and Pratylynchus penetrans root lesion nematodes
(256).
COMPARATIVE NOTES
 Buckwheat
has only about half the root mass as a percent of total biomass
as small grains (355). Its
succulent stems break down quickly, leaving soils loose and vulnerable
to erosion, particularly after tillage. Plant a soil-holding crop
as soon as possible.
Buckwheat
is nearly three times as effective as barley in extracting phosphorus,
and more than 10 times more effective than rye—the poorest
P scavenger of the cereal grains (355).
As
a cash crop, buckwheat uses only half as much soil moisture as
soybeans (299).
Seed sources. See Seed
Suppliers.
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