Page 18—Corn Talk, Lancaster Farming, Saturday, March 16, 1996
MANAGING COVER
CROPS EOR
CONSERVATION
TILLAGE
William S. Curran
Department of
Agronomy
Penn State
Cover crops are crops seeded
to provide a soil cover or barrier
from soil erosion. In addition,
cover crops can improve the
soil by adding organic matter,
nutrients, and stability, and act
as scavengers to trap leftover
nutrients that otherwise may
leach out.
Cover crop uses include
ground covers, mulches, green
manures, nurse crops, smother
craps, and forage and food uses
for animals or humans. Cover
crops can be annual or peren
nial species including certain
legumes, grasses, and non
leguminous dicots.
An understanding of the
cropping system is necessary
for selecting the proper cover
crop. Characteristics important
for cover crop selection include
life cycle, seeding date and rate,
winter hardiness, nitrogen fixa
tion or scavenging ability, feed
or forage value, and establish
ment costs.
There is no single cover crop
or system that will provide all
benefits. Therefore, exper
imentation may be necessary
before identifying suitable cov
er crop(s) for an individual
system.
Management of the cover
crop is critical for deriving the
benefits and minimizing poten
tial problems that may arise.
Planning the management
strategy well in advance will
assure the greatest success.
Management of
Cover Crops
Preplant
Considerations
Prior to cover crop
establishment, several factors
must be considered. Soil fertili
ty is an important consideration
in any cropping system. A reli
able soil test which determines
the nutrient limitations of a soil
including pH is a good place to
begin the planning process.
If certain nutrients are limit
ing, follow soil test recommen
dations for the primary crop,
keeping in mind that high fertil
ity will also maximize cover
crop growth.
Another important consider
ation is the pest history of the
field. In general, additional pest
management inputs are not
necessary when utilizing cover
crops. However, as with any
crop, pests can become a prob
lem in the cover crop system. If
possible, select fields that have
minimal pest problems when
establishing the cover crop.
Since there are generally
crop/pest associations such as
alfalfa or clover and leafhopper
or winter small grains and wint
er annual weeds, these pests can
also become a problem in the
newly planted cover crop with
in a cropping system.
Consider the herbicide
applied the previous season.
Certain herbicide residues can
carryover and injure sensitive
rotational crops. If these
residues have not dissipated
before a sensitive crop is
planted, injury or death of the
cover crop may occur.
Herbicides including atra
zine and simizine can injure
both grass and legume crops
and several of the herbicides
belonging to the sulfonylurea
and imidazolinone families
persist and can injure legumes.
Always refer to current crop
protectant product labels to be
certain of crop rotation restric
tions or other limitations before
establishing any crop.
Establishment
Options
Several options exist for
seeding cover crops, including
conventional, no-till, or broad
cast seedings.
Good seed-to-soil contact is
necessary for proper germina
tion and emergence. (When
broadcast seeding, increase the
seeding rate for proper stand
establishment.)
In general, using preplant til
lage to prepare the seedbed,
controlling weeds, and disrupt
ing insect and disease life
cycles improves cover crop
establishment.
Conventional seedbeds are
prepared by plowing, disking,
and harrowing the soil prior to
seeding. Seeding depth
depends upon the species being
sown. Generally, for most cov
er crops, small-seeded legumes
require shallow seed placement
('/« inch), while larger seeded
legumes and small grains are
generally planted 1 to
V/i inches deep.
No-till seedings can also be
successful, but planting equip
ment as well as potential pest
problems must be considered.
Excessive plant residues can
hinder uniform planting and
interfere with seedling deve
lopment. However, a no-till
drill that places the seed at the
proper depth and allows good
seed-to-soil contact is an excel-
lent seeding option.
No-till seedings are best
suited for areas where soil ero
sion is a concern. Be sure to
control live vegetation at plant
ing time with an appropriate
bumdown herbicide applica
tion (e.g., Roundup).
Broadcast seeding may also
be acceptable, although this is
often the least successful
method. Small-seeded species
such as the clovers tend to
establish better by broadcast
compared to larger seed spe
cies. Several broadcast tech
niques and timings may be
utilized.
Surface seeding with a drop
type or cyclone-type seeder
provides a uniform distribution
of seed. For larger areas, aerial
seeding by fixed-wing aircraft
or helicopter in late summer
during crop die down can be
effective. As the leaves of soy
bean plants drop off, they act as
a mulch by covering the seed
and allowing for retention of
moisture and soil protection.
Another broadcast seeding
method is frost-seeding, which
occurs during late fall or early
spring when the ground is hon
eycombed. This allows the seed
to fall into the cracks and ger
minate when the temperature
rises in the spring. Cover crop
seeding at layby or last cultiva
tion has generally not been
successful.
Suppression or
Control of
Cover Crops
Cover crops that interfere
with growth of the primary crop
defeats their benefits. Effective
control or suppression of the
cover crop is generally neces
sary before emergence of the
main crop.
Commonly used methods
include tillage, mowing, herbi
cides, or selection of species
that winterkill or have a short
life cycle.
Whatever The Crop,
Pioneer Has The
Seed And Inoculant You Need.
■ Pioneer...
Quality
Forage
Source.
>@g\ PIONEER.
> fm W4W WMKJCTj
If you're striving to increase 1
of forage crops, there's no be
than with Pioneer.
Kent L. Fritz
8 Japonica Dr.
Lititz, PA 17543
717/626-9484
Martin L. Snyder
245 Ridge Avenue, Ephrata, PA 17522
Fowl’s Feed Service Inc.
PO Box 15, Peach Bottom, PA 17563
717/548-2376
717/738-1500
Tillage not only controls but
incorporates cover crops into
the soil allowing them to
degrade quickly and release
nutrients for the primary crop.
An example of this would be a
cover crop used as a green
manure.
Moldboard plowing is often
necessary if large amounts of
cover crop biomass are present.
Chisel plowing followed by
disking may be inadequate for
certain cover crops such as
cereal rye if large amounts of
residue are present.
Mowing can successfully
control certain covers prior to
planting the primary crop if
timed properly. Mow hairy
vetch when the first puiple
flowers are visible. Mowing
vetch prior to flowering can fail
to provide adequate control and
result in both crop competition
and the production of vetch
seed which could affect future
small grain production. Mow
ing vetch after pod formation
may result in viable seed pro
duction which may impact the
primary crop.
Mow cereal grains after
heading to insure successful
control. Mowing prior to head
emergence will likely result in
regrowth from tillers.
Regrowth from cereal grains
harvested for forage in the boot
stage of development is a com
mon problem for producers that
do not use an appropriate herbi
cide program.
Certain crops such as oats
can be either mechanically
incorporated or mowed after
heading or can be used as
forage.
Pasturing with animals or
cutting for hay or silage are
viable ways of utilizing cover
crops for other means besides
soil improvements. Species
which have short life cycles or
are not winter hardy may also
be a means by which cover
crops are controlled. Generally.
Joe Hess Phares Hurst
432 South Erisman Road 175 Center Souarp Rri
7 a i7/B«aU 7 S. 5 LeoTpA?7 U 5
717/653-9490 717/656-7944
crops which are planted in the
fall, produce vegetation, and
are killed by cold temperatures
in late fall/early winter provide
adequate ground cover and are
effective in conserving and
improving soil as well as hold
ing moisture. Be aware that
winter kill occasionally may
not occur.
Control or suppression of
cover crops can be done effec
tively with herbicides. In addi
tion to product selection, appli
cation timing is important. In
general, make herbicide appli
cation at least one week ahead
of planting. This insures com
plete kill as well as some dry
down of the cover crop prior to
planting the primary crop.
Several options exist for
managing cover crops with her
bicides. See the individual
commodities sections within
the Penn State Agronomy
Guide or other related publica
tions for more information
about product selection.
Proper management of the
cover crop will ensure its suc
cess. Plan the establishment
and control strategies well
ahead of time.
Be aware of potential limita
tions and problems that can
arise with cover crop manage
ment systems. Keep expecta
tions reasonable and adapt the
management strategy when
necessary to reduce potential
problems and capitalize on the
benefits.