TROUT
RUN, Pa. -- Growing cover crops for a full year between
cash crops helps Eric and Anne Nordell control virtually every
type of weed nature throws at their vegetable farm--even quackgrass.
The couple experimented with many different cover crops on
their north-central Pennsylvania farm before adapting a system
used to successfully battle quackgrass on a commercial herb
farm in the Pacific Northwest. Between cash crops, the Nordells
grow two winter cover crops to smother weeds. A brief stint
of aggressive summer tillage between the two cover crops keeps
annual weeds from setting seed. Regular use of cover crops
in their half-acre strips between rows of vegetables also
improves soil quality and moisture retention while reducing
erosion.
"Vegetable crops return very little to the soil as far
as a root system," says Eric, a frequent speaker on conservation
practices at conferences in the Northeast. "You cut a
head of lettuce and have nothing left behind. Growing vegetables,
we're always trying to rebuild the soil."
The Nordells' short growing season--which typically ends
with the first frost in September--makes it challenging to
squeeze in cover crops on their six cultivated acres. Yellow
blossom sweetclover is overseeded at 20 to 24 lb./A into early
crops such as onions or spring lettuce. Lettuce is overseeded
a week or two after planting but before leaves open up to
trap sweetclover seeds, while onions are overseeded near harvest.
The Nordells walk up and down every other row with a manual
Cyclone seeder (canvas bag with a hand-crank spinner). They
harvest the cash crop, then let the clover grow through summer.
Yellow blossom sweetclover--one of the best cover crop choices
for warm-season nitrogen production--puts down a deep taproot
before winter if seeded in June or July, observes Eric. "That
root system loosens the soil, fixes nitrogen, and may even
bring up minerals from the subsoil with its long tap root."
He points out that the clover alone would not suppress weeds.
The sole-seeding works on their farm because of their successful
management efforts over a decade to suppress overall weed
pressure by crop rotation and varied cover crops.
In spring, the sweetclover grows until it is about knee-high
in mid-May. Then the Nordells clip it just before it buds.
They let the regrowth bloom to attract pollinators and beneficial
insects to the field, before clipping it again in July. In
early- to mid-July, the Nordells moldboard plow the sweetclover
to kill it. They leave the ground in bare fallow, working
it again with a springtooth harrow to hit perennial weeds
at the weakest point of their lifecycle.
After that, the couple harrows every two to three weeks to
bring weed roots and rhizomes to the soil surface, where they
bake in the summer sun. The harrowing also kills flushes of
annual weeds before they can set seed. After five years in
this weed-killing rotation, the Nordells were able to cut
back on harrowing, which they now coordinate with rainfall
and weed pressure. In the unusually dry summer of 1997, for
example, they did not harrow at all after plowing.
In mid-August, the Nordells plant a second, overwintering
cover crop. In this rotation, they seed a mix of rye and hairy
vetch. They broadcast and lightly incorporate about 80 pounds
rye and 30 pounds vetch per acre. The rye establishes quickly,
putting on good growth both above and below the surface, while
the vetch fixes nitrogen. Another combination is yellow, red
and white clover in a 2:2:1 ratio by volume.
"We're looking for a green field by Labor Day,"
Eric says. "We want a good sod before we get our first
freeze." Rye and vetch are a popular combination to manage
nitrogen. The rye takes up excess N from the soil, preventing
leaching. The vetch fixes additional nitrogen which it releases
after it's killed the following spring prior to planting the
next cash crop. With the August seeding, the Nordells' rye/vetch
mixture produces most of its biomass in fall.
The Nordells plow the rye/vetch mix after it greens up in
late March to early April, working shallowly so as not to
turn up as many weed seeds. They forego maximum biomass and
N for earlier planting of their cash crop--tomatoes, peppers,
summer broccoli or leeks--around the end of May. The bare
fallow during mid-summer plus early spring incorporation of
overwintering cover crops are the best preventive to slugs
and grubs, they have found.
Thanks to their weed-suppressing cover crops, the Nordells
typically spend less than 10 hours a season hand-weeding their
three acres of cash crops, and never need to hire outside
weeding help. "Don't overlook the cover crops' role in
improving soil tilth and making cultivation easier,"
adds Eric. Before cover cropping, he noticed that their silty
soils deteriorated whenever they grew two cash crops in a
row. "When the soil structure declines, it doesn't hold
moisture and we get a buildup of annual weeds," he notes.
The Nordells can afford to forego a cash crop to keep half
their land in cover crops because their tax bills and land
value are not as high as market gardeners in a more urban
setting. "We take some land out of production, but in
our situation, we have the land," Eric says. "If
we had to hire people for weed control, it would be more costly."
Excerpted from Managing Cover Crops Profitably,
Second Edition, by the Sustainable Agriculture Network, reprinted
2000, SAN, Beltsville, MD, pp. 34-42.
Complete text: http://www.sare.org/handbook/mccp2/index.htm
To order: http://www.sare.org/htdocs/pubs/ToOrder.html
To contact SAN off the Web: PHONE: (301)
504-6425; FAX: (301) 504-5207; EMAIL: san@sare.org.
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