For
more information on this research and on no-till
cover crop mulch systems for organic vegetable
production, contact: Dr. Ron Morse, Professor
of Horticulture, Virginia Tech., Blacksburg, VA
24061; tel. 540-231-6724; e-mail morser@vt.edu.
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Why and how organic no-till
got started
Weed control is often cited as the single greatest
challenge in organic crop production. In relying
on tillage and cultivation rather than chemical
herbicides to manage weeds, organic growers risk
greater soil degradation, organic matter loss
and erosion. Cover crops suppress weeds, add organic
matter and nitrogen, mobilize nutrients, hold
and improve the soil, and harbor beneficial insects.
However, when the cover crop is turned under prior
to planting the primary crop, the tillage required
to prepare a seedbed burns up organic matter,
degrades tilth and stimulates weeds to emerge—which
means yet more cultivation and associated costs.
Since the mid 1980s, researchers at the New Alchemy
Institute, The Rodale Institute Experimental Farm,
and several land-grant universities have experimented
with managing winter annual cover crops such as
rye, hairy vetch, and crimson clover without tillage
prior to planting a vegetable crop. These cover
crops can be killed mechanically by mowing or
rolling after they begin to flower and shed pollen
(usually in mid to late May), and the resulting
mulch can suppress weeds for six weeks or more.
During this time, tomatoes, broccoli or other
vegetables can be transplanted and established
so that later-emerging weeds have little impact
on yield.
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We look forward to learning
more about the effects of no-till on the soil,
crop yields, weed and pest levels, and net economic
returns to the farmer. Stayed tuned to www.newfarm.org
for updates on project findings over the next
few years.
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The pros and cons of no-till
cover crop management
The potential advantages of this system include
greater cover crop biomass production (since it
is allowed to grow until a week or so before vegetable
planting), and much less loss of organic matter
through tillage. Together, these can greatly enhance
annual organic inputs and thereby support higher
levels of 'active organic matter,' which correlates
closely with soil quality. In addition, the cover
crop mulch conserves soil moisture, curbs weed
seed germination, and provides habitat for ground-dwelling
predators of insect pests.
On the other hand, continuous no-till can eventually
lead to perennial weed problems or cause some
soils to become somewhat compacted. Thus organic
growers may need to practice 'rotational tillage,'
working the soil before planting cover crops in
some years. Research results at The Rodale Institute
Experimental Farm suggest that this may be the
case. How often tillage is needed and whether
soil quality can still improve under rotational
tillage are two of the questions Morse’s
research will address.
One other possible drawback is that the cover
crop mulch will keep soil temperatures lower so
that the system may not work where early harvests
are desired, especially for warm season crops.
However, later plantings of the same crops may
benefit from the soil-cooling and moisture-conserving
effects of mulch, especially in hot climates or
in drought years.
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“The one thing
I want to accomplish before I retire is to establish workable
systems for organic no-till vegetable production using cover
crops,” Dr. Ron Morse told me in one of our first meetings.
A professor of horticulture at Virginia Tech, in Blacksburg,
Va., Morse has been working for upwards of two decades on soil-conserving
systems for vegetable production in hilly Appalachia. Using
high-biomass cover crop mixtures like winter rye and hairy vetch
killed to form an in situ mulch, he has helped growers save
tons of soil and reduce weed control costs. More recently, he
has worked on herbicide-free systems for organic growers.
Morse was born and raised on a family farm in Utah. He worked
with his father and three brothers in their 10-cow dairy,
where “we did everything together, which taught us a
strong ethic of cooperation and responsibility.” He
went to college at Utah State, then earned a Ph.D. in Horticulture
at Michigan State. His professional commitment to making farming
more sustainable for both land and grower led naturally to
no-till cover crop systems.
Morse began this line of research in the winter of 1978-79,
when he received a letter from an extension agent in mountainous
Carroll County, Va., with a photo of U.S. Route 58 blocked
by a mass of soil washed away from an adjacent cabbage field.
The caption read simply, “Help!” Morse knew the
first step was to stop plowing. So he put a graduate student
to work at Virginia Tech’s experimental farm, growing
rye cover crops for no-till vegetable planting. Initially,
they planted by hand, digging holes to plant cabbage through
herbicide-killed rye. It worked!
The next hurdle was to mechanize the transplanting. At first,
researchers modified a Holland transplanter by adding a front
coulter to slice through cover crop residues, which worked
well in moist, mellow soils. Farmers got interested fast—but
then a drought struck, and the Holland planter repeatedly
broke when pulled through dry, untilled soils. So Morse and
a team of others built the first Sub-Surface Tiller-Transplanter
(SST-T) in 1990. The front component is a durable sub-surface
tiller that prepares a narrow strip of soil, loosening as
deep as 8 inches. The second is a no-till transplanter that
sets transplants into the prepared strip. It has a double-disk
opener ahead of the planting shoe, and the press wheels are
modified so that they close the untilled soil around the plant.
By 1996, improved versions of the SST-T could lay drip tape,
apply organic or conventional fertilizer (in-row or side-band),
and water in the transplant. Different attachments can be
used for a variety of vegetable starts, seed potatoes or large
seeds like beans.
If you build it, they will come
When word of early successes got out, Morse received an avalanche
of calls from farmers and extension agents wanting to see
demonstrations and try the SST-T themselves. Many calls came
from organic farmers and sustainable agriculture organizations
interested in better weed control with less soil-damaging
tillage. So the herbicides had to go—and winter annual
cover crops can be killed mechanically. Morse uses a flail
mower or a roller-crimper to convert a live, standing cover
crop into a mulch through which the SST-T can easily operate.
(A bush-hog or a sicklebar mower leaves the cover crop stems
helter-skelter, which can jam the planter.) Broccoli, potatoes,
tomatoes and other vegetables have been successfully planted
into flail-mowed cover crops at Virginia Tech’s Kentland
Agricultural Research Farm (hardiness zone 6b) and on several
organic farms in the region. “The key to success is
to grow really good cover crops,” Morse emphasizes,
“at least three tons dry matter per acre. I like the
rye and vetch [mixture] to be five or six feet high, and nice
and thick. Otherwise, you don’t get weed control.”
Morse and his colleagues are also experimenting with other
cover crops and planting seasons. Frost-tender annuals like
German or foxtail millet, pearl millet, sorghum-sudan hybrid
(sudex), cowpeas, forage soybean, sunn hemp, or lablab bean
can be planted in early summer and mowed in August for no-till
fall brassicas, or planted later in summer and grown until
killed by fall frost. Sudex produces tremendous biomass, and
suppresses weeds through competition and allelopathy (the
release of substances that inhibit weed growth). Mowing sudex
when it is chest high stimulates roots to penetrate deeper,
which opens the subsoil and may enhance allelopathy. Morse
mixes stiff-stemmed grasses or sunn hemp with more succulent
legumes to maximize biomass and ground cover, and to balance
the carbon to nitrogen ratio. Fall broccoli planted no-till
into a flail-mowed cowpea and sunn hemp mixture gave yields
similar to conventional-till broccoli.
Oats, lana vetch and berseem clover tolerate frosts to 20
degrees but do not over-winter, so they can be planted in
late summer to create a winter-killed mulch for no-till planting
of brassicas or other early spring crops the next year. When
frost kills the cover crop, mowing is not needed.
Cover crop systems are limited only by
your imagination
The possibilities are limited only by the imagination, of
which Morse has plenty. He grows self-seeding winter cover
crops such as little barley (considered a weed by some) and
subterranean clover, which die down in early summer and come
back from seed in the fall. In mid July 2003, he planted ‘Arcadia’
broccoli no-till into a little barley and sub clover residue.
Recently, he began experimenting with garlic, which is normally
planted in October and immediately mulched with hay or straw.
This fall, he planted garlic no-till into frost-killed sudex,
sunn hemp and lablab beans.
For no-till vegetables, Morse usually forms a raised bed
just before planting the cover crop. At Kentland Farm, he
plants “companion grass,” a mixture of dwarf perennial
ryegrass and creeping red fescue, in the alleys between beds
and up the bed shoulders. This grass mixture requires only
two or three mowings a season, effectively suppresses weeds,
and stabilizes the beds so they can be used for several years
without re-forming. In the future, he may augment this combination
with low-growing perennial clovers to provide long-term habitat
for beneficial insects.
No-till, no-herbicide cover crop management and vegetable
planting offer a vital soil-building weed management strategy
for organic growers and a practical solution to the kind of
soil loss that prompted the Carroll County extension agent’s
original call for help. Recent trials suggest that this approach
may find broad application in diversified vegetable production.
The SST-T, manufactured by B & B No-Till in Laurel Fork,
Va., costs between $5,000 and $10,000 for a one-row planter
(depending on whether a fertilizer hopper and/or drip tape
layer are included). However, some 25 regional Soil and Water
Conservation Districts have purchased these planters and make
them available to growers on a rental basis. Morse is also
working on other ways to make this system available to small-scale
growers who cannot afford to purchase the SST-T.
Future work will reach out to more growers
Morse’s work thus far has attracted support for a new
round of soil-saving experiments over the next three years.
During 2002-03, Morse was awarded grants from the Southern
Region SARE program and the USDA Cooperative State Research,
Education and Extension Service (CSREES) to conduct further
studies on no-till organic broccoli, potato, pepper and summer
squash. He hopes to extend no-till cover crop management to
a wider range of cover crops, vegetable species, and planting
seasons, and to incorporate state-of-the-art biological pest
management practices into an integrated organic production
system. (Editor’s note: The author, Mark Schonbeck
was also invited to participate in two of these projects as
farm outreach coordinator in Virginia.)
Dr. Richard McDonald, one of the region’s foremost
consultants in bio-control, will help implement 'farmscaping,'
or planting strips of flowers and herbs to provide forage
and habitat for natural enemies of key vegetable pests. The
experiments will compare no-till management of the cover crop
with the traditional practice of turning the cover crop under
as a green manure several weeks before planting. They will
measure cover crop biomass, weed suppression, pest and disease
levels, marketable crop yields, and soil biological and physical
properties in the two systems.
In addition to research at Virginia Tech and University of
Georgia, the projects will include an outreach component in
which organic farmers in Virginia, North Carolina and Georgia
will participate in on-farm trials comparing no-till cover
crop management with the growers’ normal practices within
a three-year vegetable rotation. Field days will be held during
the 2004 and 2005 seasons, and the host farmers will also
participate in project presentations at conferences.
Extremely wet weather during spring and summer of 2003 delayed
the establishment of many of these experiments. Morse and
his colleagues waited for weeks on end for the soil to get
dry enough to plant cover crops. We finally got a break this
fall, and cover crops have been successfully established on
six acres of organic-transition land at Kentland Farm. On-farm
trials also got a late start, but soil samples have now been
taken and cover crops sown for vegetable planting in the 2004
season.
Mark Schonbeck coordinates the outreach component of
SARE- and CSREES- funded organic no-till research projects
in Virginia. He is also editor of The Virginia Biological
Farmer, the 12-page quarterly newsletter of the Virginia Association
for Biological Farming. You can contact Mark at 540-745-4130,
mark@abundantdawn.org.
For more information on VABF, write to VABF, P.O. Box 1003,
Lexington, VA 24450; visit the web site www.vabf.org, or contact
our office manager, Linda Davis at 540-463-6363.
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