Managing Cover Crops Profitably - Valley Crops Home

Full-Year Covers Tackle Tough Weeds
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 halfacre
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,
ceded by LANA vetch, which produces more N than
other covers. Before tomatoes, common vetch works
best. A mixture of purple vetch and oats is grown
before dry beans, and a mix of sorghum-sudangrass
and cowpeas precedes safflower.
In order to get maximum biomass and N
production by April 1,LANA vetch is best planted early
enough (6 to 8 weeks before frost) to have good
growth before “winter.”Disked in early April,LANA provides
all but about 40 lb.N/A to the sweet corn crop.
Common vetch, seeded after the corn, can fix most
of the N required by the subsequent tomato crop,
with about 30 to 40 lb.N/A added as starter.
A mixture of sorghum-sudangrass and cowpeas is
planted following tomato harvest. The mixture
responds to residual N levels with N-scavenging by
the grass component to prevent winter leaching.
The cowpeas fix enough N for early growth of the
subsequent safflower cash crop, which has relatively
low initial N demands. The cover crop breaks
down fast enough to supply safflower’s later-season
N demand.
38 MANAGING COVER CROPS PROFITABLY