ROCK HILL, S.C. --Your crop rotation and
cover crops can do a lot for you -- and you had better be
sure they do it!
That was the messageto organic farmers who traveled to Rock
Hill SC in early November to attend the annual Sustainable
Agriculture Conference sponsored by the Carolina Farm Stewardship
Association (CFSA).
The group’s 18th annual conference had a cluster of
workshops on aspects of managing selected crops to improve
soil fertility, increase water retention, enhance soil organic
matter, manage disease and insects and keep down weeds for
no-till transplanting.
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S
p o n s o r B o x
Carolina Farm Stewardship Association (CFSA)
Purpose:
CFSA is a membership organization of more than
800 farmers, processors, gardeners, businesses
and individuals in North and South Carolina who
are committed to sustainable agriculture and the
development of locally-based, organic food systems.
Founded: In 1979 by a group
of farmers, gardeners and consumers to support
each other in their efforts to foster the growth
and distribution of organic food in the Carolinas.
Mail: PO Box 448, Pittsboro,
NC 27312
13 Hillsborough Street Suites 3 & 8, Pittsboro,
NC 27312
Contact info: Tony Kleese
www.carolinafarmstewards.org
(site under re-construction, click “Farmer
Resources”)
cfsa@carolinafarmstewards.org
(919) 542-2402 |
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What is crop rotation? Jim Riddle, an organic certification
expert from Minnesota, defined it for a workshop at the conference
as the practice of alternating the crops grown on a specific
field in a planned pattern or sequence in successive crop
years so that crops of the same species, or family, are separated
year-by-year by other crops in a beneficial way.
One basic rotation might be to plant a rye cover crop right
after corn in a corn/soybean rotation. The rye will scavenge
residual nitrogen and provide ground cover in the fall and
over winter. When it is killed in early spring, the rye provides
a water-conserving mulch and suppresses early-season weeds
for the following soybean crop.
A subsequent cover-cropping step could be planting hairy
vetch (a winter annual legume) behind the soybeans to provide
nitrogen for corn the following spring. (For more on the basics
of rotation, see “Overview of cover crops and green
manures” in the “Fundamentals of Sustainable Agriculture”
series at http://attra.ncat.org/attra-pub/PDF/covercrop.pdf)
An optimal crop rotation for organic grain production, said
Riddle, would:
–Maintain or improve the organic matter level of the
soil.
–Provide for pest management.
–Make it possible to manage deficient or excess plant
nutrients.
–Improve erosion control.
To make a crop rotation work, find the highest return for
each cash crop included. Determine if a cover crop can be
grown on contract or can be fed to your livestock. Find out
if seed is available when you need it, and if can you meet
any of the market’s quality demands.
You also want to look for special agronomic characteristics
in rotation crops that are serving essentially as cover crops,
i.e. have their primary value in benefiting the soil or the
next crop, rather than to be harvested and sold. The ideal
cover crop would germinate and emerge fast, compete effectively
in the field with other plants and weeds, tolerate adverse
climatic and soil conditions, suppress easily and be inexpensive
to establish.
You are not likely to find a cover crop with all these characteristics,
Riddle explained. You must set priorities, determine the top
priorities for your cover crop and then choose an appropriate
species. Be sure to find out which species do well in your
region.
Selecting crops for insect control
Rotation and cover crops definitely have a role to play in
insect control, said Debbie Roos, an agricultural extension
agent from Chatham County NC who spoke on organic insect management.
As insects overwinter in soil and debris, they will re-infest
the new crop if it is susceptible. Pest populations can build
up. The solution is to rotate with non-susceptible crops so
that pests have no food or shelter. Leave as much time as
possible between related crops to make conditions difficult
for the pests.
Crop rotation is not effective for controlling pests with
a broad host range. There are three questions to ask yourself,
Roos said:
-- How long can the pest persist in the field without any
host?
-- Can it invade from other areas?
--Does it survive well on other hosts when your crop is not
present?
The more holistic but less precise approach is to use good
bugs to fight the pest varieties. Here, cover crops can provide
a valuable habitat and food source for beneficials, allowing
their populations to build up early in the season before the
emergence of pests. Using companion plants in a sustainable
program has been suggested as a pest control strategy. This
approach could involve attractant (trap) crops like caraway,
fennel and hyssop. There are thought to be some repellent
crops: catnip and tansy are said by some to repel aphids,
while artemisia is said to repel flea beetles. For Roos, the
value of all this remains rather vague. In some situations,
alleged companion plants have been shown to actually increase
pest populations.
"There are lots of recommendations about companion crops
out there with little scientific evidence on a field scale,"
said Roos. "We need more study before recommending."
Growing a diverse mixture of crops, in alternate rows across
a field, helps attract beneficials and impede pests. Roos
is conducting on-farm research to learn more about how farmers
may benefit from beneficial insect habitat.
When your cover crop becomes a weed
Any cover crop species will work better with some crops than
with others. Kenny Haines of Looking Back Farms in Tyner NC
had good success with a rye/hairy vetch cover crop back when
he was growing mainly fruits and vegetables. But then he started
planting grains, and the hardseeded vetch presented a problem.
“It’s cheap and grows vigorously, but it can
easily go to seed and come up in your wheat,” said Haines.
“For that reason, we have had to get away from vetch.”
Much of his land is in a rotation of corn followed by wheat
and soybeans, though rye/vetch still has an occasional use
if Haines can place it well before wheat. He also grows watermelons
occasionally in this rotation.
Some of the participants in the discussion suggested crimson
clover, sweet clover or red clover as substitutes for the vetch.
Haines likes to till as little as he can, but because of
a problem with the cover crop, he is reluctant to go 100 percent
no till. “If you no-till soybeans into wheat straw,
you have no defense if weeds come up,” he said. “If
I plow [on the other hand], I have a range of cultivators
to choose from to do the job.”
New varieties make small grains a
better tool
If you need a small-grain crop in a rotation, either as a
cover crop or cash crop, the most important step is to choose
the right grain and the most suitable variety. There are varieties
of all the Southeast’s major feed grains -- wheat, oats,
barley, triticale and rye – that will all do well in
sustainable agriculture, said Paul Murphy, an NC State University
plant breeder.
That is in part because breeding programs have followed priorities
that are as important to organic agriculture as they are to
conventional farming. “Traditionally in this area, all
the grains have been considered low-input crops,” said
Murphy. “Farmers anticipate resistance to all the important
pests in the varieties that are available, since they don’t
want to have to treat for them.” That means there are
plenty of varieties for the organic/sustainable farmer to
choose from.
“Good yield and quality should be factors in a variety
choice,” said Murphy. “But also take into consideration
resistance to powdery mildew, Hessian fly and leaf rust. If
you select carefully among the numerous varieties available,
you will be able to get that resistance with the other characteristics
that you need."
Wheat: Among wheat varieties, a new introduction
called “NC Neuse” (after the Neuse River) could
prove to be a good choice in organic programs, said Murphy.
It is resistant to powdery mildew and leaf rust and is also
moderately resistant to fusarium head blight and Hessian fly.
There may well be a benefit to choosing a hard red winter
wheat variety rather than a soft red winter wheat, the type
traditionally grown in the south, said Murphy. Research at
NC State on identification of suitable hard wheats is progressing
rapidly, and recommendations will be available for planting
in fall 2004.
Barley: A trend in small-grain breeding
that could provide some tools for sustainable agriculture
growers is the recently developed breeding goal of “hull-less”
seedheads. One such variety, a barley called “Doyce,”
should be available in 2004 from Virginia Tech. It grows and
looks like regular barley until it is mature. During combining,
the hulls separate from the grain. It has attracted some interest
as a high-energy animal feed and also as feedstock for ethanol
production.
Oats: Thishe new characteristic has not
been confined to barley. A new hull-less variety of oat called
“NC Hulless” is also available. Its hulls are
threshed off the seed so you end up with a higher energy,
higher protein feed. “This oat has a role to play in
hog, poultry and perhaps even fish farming,” said Murphy.
It could find a place in horse-feeding programs, as well.
Triticale: This grain -- a cross between
wheat and rye -- has inherent insect and disease resistance
that might make it a good fit in sustainable agriculture.
“We have observed in our breeding nurseries that triticale
has high levels of disease- and insect resistance and drought
tolerance,” said Murphy. “Its grain has a high-quality
protein that makes it suitable for hog and poultry feed, and
many cultivars produce abundant leafy growth in late winter
and early spring with potential for grazing or silage production.
“It performs well in the southeast and is relatively
easy to produce. It has a niche, but as with hull-less barley
and oats, make sure you have a market for it before you grow
it,” he cautioned. N.C. State University released its
first triticale cultivar, “Arcia,” in 2001.
Rye: Rye is popular as a cover crop because
it has the highest level of allelopathy – weed suppression
– of any of the common small grains.
“There is a danger, however, if you are planting a
small-seeded crop like lettuce behind rye,” said Murphy.
“Rye interferes with weed-seed germination, and so it
might interfere with a small- seeded crop. Transplants would
face less of a risk.”
Chris Bickers is a freelance writer-photographer in Raleigh,
NC.
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