Managing Cover Crops Profitably - Valley Crops Home

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.”
See Recommended Resources (p. 162) to
order a video describing this system.
▲ Precaution. If you are not using any herbicides,
vetch could become a problem in the
California system.Earlier kill sacrifices N,but does
not allow for the production of hard seed that
stays viable for several seasons.
COVER CROPS FOR COTTON PRODUCTION
In what would otherwise be continuous cotton
production, any winter annual cover crop added
to the system can add rotation benefits, help
maintain soil productivity, and provide the many
other benefits of cover crops highlighted
throughout this book.
Hairy vetch, crimson clover, or mixtures with
rye or another small grain can reduce erosion,add
N and organic matter to the system. Drill after
shredding stalks in the fall and kill by spraying or
mowing prior to no-till seeding of cotton in May.
Or, aerially seed just before application of
defoliant. The dropping leaves mulch the cover
crop seed, aiding germination. Rye works better
CROP ROTATION WITH COVER CROPS 39