Southeastern U.S. Vegetable Crop Handbook - 2021 - 27

dates. For sandier coastal plain soils, rye is the preferred small
grain cover crop. As previously discussed, seeding depth varies
from ½ to 1½ inches, depending on soil texture. Planting methods
are the same as described for legumes.
Types Of Winter Cover Crops: Legumes
A wide range in planting dates exists for most legumes, though best
results are obtained with early plantings. Early seeding dates are
easy to meet with legume cover crops following spring vegetables.
Because Cahaba White Vetch possesses little winter hardiness, it is
not adapted to western NC and the northern regions of other southeastern
states. Freeze damage has also occurred with Austrian Winter
Pea in higher elevations (above 2,500 feet). Avoid planting late
otherwise you increase the risk of winter kill. For state specific recommendations
for planting dates, seeding dates and management
for legume cover crops, consult your local Extension office.
SEEDING RATES AND DEPTHS
REGAL GRAZE LADINO CLOVER: broadcast 15 to 20 lbs/A
(seeding depth: 1/4 in.). Can be bedder-disked for bare ground or
plasticulture forming a between row mulch useful for conventional
or bare ground production. Inhibits yellow nutsedge and can survive
year round with moisture.
CRIMSON CLOVER: broadcast 20 to 25 lbs/A;
drill 15 to 20 lbs/A (seeding depth: ¼ - ½ in.)
HAIRY VETCH: broadcast 20 to 30 lbs/A;
drill 15 to 20 lbs/A (seeding depth: ½ - 1½ in.)
CAHABA WHITE VETCH: broadcast 20 to 30 lbs/A;
drill 15 to 20 lbs/A (seeding depth: ½ - 1½ in.)
AUSTRIAN WINTER PEA: broadcast 25 to 35 lbs/A;
drill 20 to 25 lbs/A (seeding depth: ¾ - 1½ in.)
When seeding, use shallow planting depths for finer-textured,
clayey soils and deeper depths for coarse-textured, sandy soils.
Drilling into a conventional seedbed is the most reliable way to
obtain a uniform stand. A no-till grain drill can be used successfully,
provided residue from the previous crop is not excessive
and soil moisture is sufficient to allow the drill to penetrate to the
desired planting depth. Seeds can be broadcast if the soil has been
disked and partially smoothed. Cultipacking after broadcasting will
encourage good soil/seed contact. Crimson clover, in particular, responds
favorably to cultipacking.
MIXING GRASS AND LEGUMES: Planting a single grass or legume
may be necessary, but combining a grass and legume together
may prove better than either one alone. Grasses provide
soil protection during the winter and also produce great forage or
plow-down organic matter. Legumes do not grow well during the
winter, but late spring growth is abundant and produces high protein
forage and nitrogen for the following crop. Crimson clover is
a legume to grow in combination with a grass. Crimson clover's
height matches well with barley, wheat, and oats, but may be shaded
and outcompeted by rye. Hairy vetch has been sown with grass
cover crops for many years, using the grass/vetch combination as a
hay or plowdown.
2021 Vegetable Crop Handbook for Southeastern United States
BIOFUMIGATION AND COVER CROPS: Biofumigation is the
horticultural practice of using naturally produced volatile chemicals
or allelochemicals to suppress soil-borne pathogens, pests,
and weeds. These allelochemicals (specifically isothiocyanates
produced when glucosinolates break down) are produced when
crops in the Brassica family decompose in the soil.
Brassica crops have been used extensively as winter cover
crops and as " break crops " where the residues are tilled into the
soil for their biofumigation effect. They have also been used in rotations,
where the Brassica crop is harvested for sale and then the
remaining residue is tilled-in for the biofumigation effect. There
are several commercially available cover crops that have been used
for biofumigation. " Caliente 119 " (a mixture of oilseed radish and
mustard), oilseed radish, " Florida Broadleaf Mustard " , garden
cress, penny cress, " Dwarf Essex " rape, and several canola varieties
have been reported to have biofumigation potential.
In much of the southeast region of the U.S., these crops can be
seeded in fall and over-wintered, or direct seeded in early spring. In
either case, the crop should be chopped and tilled-in when it is in
the early flowering stage in order to achieve the maximum biofumigation
potential. The early flowering stage is the point at which the
allelochemical concentrations are their highest. Seeding rates range
from 4 to 20 lbs/A and will vary with location and seed size (generally,
the smaller the seed size, the lower the rate).
These crops respond and produce more biomass and more biofumigation
potential when provided with 30 to 90 lbs/A N fertilizer
at planting. These crops grow rapidly and can normally be plowed
down in 6 to 10 weeks. In areas where the average last spring frost
is 1 May or later, only spring planting is recommended. Optimal
results occur when the Brassica cover crop is chopped, and tilled
completely into the top 6 to 8 inches of soil and then watered in
thoroughly. Watering in will help trap the volatile compounds into
the soil. Brassica seed meals (specifically mustard seed meal) may
also be utilized for biofumigation. Mustard seed meal is highly
concentrated in volatiles and also provides a partial source of organic
fertilizer for the following crop. Mustard seed meal can be
used as a biofumigant by spreading it like a fertilizer, tilling into
the soil, and then watering in to trap the volatiles.
PLOWDOWN: Plowing early defeats the purpose of growing cover
crops as little biomass will have been produced by the cover crop.
In the case of legume cover crops, they require sufficient time to
develop biomass which an early plowdown would prevent. If you
need to plow early, use a grass cover crop (rye) that produces good
fall growth and will provide maximum biomass for incorporation.
Allow 3-6 weeks between plowdown and planting.
TRANSPLANT PRODUCTION
These recommendations apply to plants grown under controlled
conditions IN GREENHOUSES OR HOTBEDS. (Field-grown
plants are covered under the specific crop.) A transplant is affected
by factors such as temperature, fertilization, water, and spac ing. A
good transplant is one that has been grown under the best possible
condi tions.
Table 5 presents optimum and minimum temperatures for seed
germination and plant growth, time and spacing (area) requirements,
and number of plants per square foot for a number of economically
important vegetable crops in the southeastern US.
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Southeastern U.S. Vegetable Crop Handbook - 2021

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