Managing Cover Crops Profitably - Valley Crops Home

shows release may be faster. There, red clover
and hairy vetch released 70 to 75 percent of their
N in the first season (329).
Marianne Sarrantonio
RED CLOVER (Trifolium pratense)
weeks. If not mechanically killing, spray with 2
quarts of glyphosate and a quart of 2,4-D ester per
acre. The daytime high air temperature should be
above 60 F (so that the plants are actively growing).
When soil temperature drops below 50 F,
biological decomposition slows to the point that
mineralization of N from the clover roots and topgrowth
nearly stops (183).
Field Evaluation
In Michigan, plant counts are used to estimate
roughly how much N a clover stand will contribute
to the immediately following crop. The
formula is 30 + 0.30 x % stand,where 100 percent
stand is five to six plants per square foot in the
second year of growth. So a field where your
counts showed an average of six plants per square
foot would contribute about 60 lb. N/A (30 +
[0.30 x 100] 30 = 60). With four plants per square
foot, percent stand is 4/6 or 66 percent, so the N
contribution is 50 lb./A (30 + [.30 x 66] 20).
The Michigan field calculation reflects the conventional
rule of thumb that about half of the total
N fixed by a legume will mineralize during the following
growing season and be available to that
season’s crop (183). However,Wisconsin research
Rotations
Rotation niches for red clover are usually between
two non-leguminous crops. Spring seeding with
oats or frostseeding into a wheat crop are common
options. The intersowing allows economic
use of the land while the clover is developing.
This grain/red clover combination often follows
corn, but also can follow rice, sugar beets, tobacco
or potatoes in two-year rotations. For threeyear
rotations including two full years of red
clover, the clover can be incorporated or surfaceapplied
(clipped and left on the field) for green
manure, cut for mulch or harvested for hay (91).
Red clover in a corn>soybean>wheat/red
clover rotation in a reduced-input system out-performed
continuous corn by $53 per acre in a fouryear
Wisconsin study. The legume cover crop
system used no commercial fertilizer, no insecticides
and herbicides on only two occasions—
once to-spot spray Canada thistles and once as a
rescue treatment for soybeans. Rotary hoeing and
cultivating provided weed control.
Gross margins were $195 for the corn>soybeans>wheat/red
clover and $151 for continuous
corn using standard agricultural fertilizers,insecticides
and herbicides. Top profit in the study went
to a corn>soybean rotation with a gross margin of
$209, using standard inputs (218, 326).
Pest Management
If poor establishment or winterkill leads to weed
growth that can’t be suppressed with clipping or
grazing, evaluate whether your anticipated cover
crop benefits warrant weed control. MCPA is
labeled for broadleaf weed control in winter
annuals with clover seedings, but care must be
taken to avoid seedling injury (183).
Never plant dry beans or soybeans after clover
unless the cover has been thoroughly incorporated
by plowing. Limited herbicide options may be
unable to control clover escapes that survive in
the bean crop (183).
Root rots and foliar diseases typically kill common
medium red clover in its second year,making
130 MANAGING COVER CROPS PROFITABLY