Cover Crops
Terry E. Poole
Extension Agent
Frederick County, MD
* Cover crops are a valuable
tool in agricultural production
Defining Your Purpose
Cover species selected should have many
of the following traits:
*fast germination & emergence
*competitiveness
*tolerance to adverse climatic and
soil conditions
*ease of suppression
*fertility benefits
*low-cost establishment
What is a Cover Crop?
• A crop whose main purpose is to
benefit the soil or other crops in one or
more ways, but is not intended to be
harvested for feed or sale.
Benefits of Cover Crops
• Cuts fertilizer bill
- “fixed” nitrogen
- recycles nutrients
• Reduces soil erosion
• Reduces water pollution
• Improves soil tilth
- physical properties of soil
favorable
to plant growth
Benefits of Cover Crops
• Cuts herbicide costs
- mulch
- alleopathy
• Reduces insect pests
• Reduces disease organisms and
nematodes
• Provides wildlife forage and habitat
N Furnished by Cover Crops
alfalfa, alone
80 lb
ladino clover
80 lb
red clover, alone 80 lb
common vetch 50 lb
hairy vetch
100 lb
cowpeas
40 lb
mostly grass
0 lb
alfalfa/grass
60 lb
crimson clover 80 lb
red clover/grass 40 lb
lespedeza
30 lb
winter peas
90 lb
soybeans
35 lb
Disadvantages of Cover Crops
• Can be expensive to establish
• Can be difficult to eliminate
• Can become a weed
• Can compete with your crop
• Not a cash crop; lose income from crop
- benefits are more indirect
• Some cover crops are more flexible than
others with seeding times
What are the goals for your Cover Crop?
• How long do you need it?
• Is it for erosion control, or other
environmental protection function?
• Will wildlife need it for forage, or cover?
• Is there a need for weed suppression?
• Does the soil need organic matter?
• Are there pest suppression needs? What?
• Be sure to allow the cover crop time to do
what it is supposed to do.
Cover Crops and Trees
A couple of notes:
• Shade from trees may stunt cover crop
growth.
•Some cover crops may compete with
trees for moisture.
•Tillage to establish cover crops can
damage tree roots and also cause soil
compaction.
Cover Crop Establishment
• No till seeding
- no till drill
- broadcast into a standing crop
- frost seeding
• Conventional seeding
- plow/disk
- broadcast/drill
Cover Crop Establishment
• Inoculate legumes
- fresh, species specific inoculant
• Match species to goals and soil
type/conditions
• Soil test and follow recommendations
• Use good, live seed
• Control weeds as much as possible
pH Effect on Soil Nutrients
Soil Conditions Affect Plants
• Droughty
Yes: alfalfa, tall fescue, reed canary,
orchardgrass, red clover, etc.
No: kentucky bluegrass, ryegrass,
small grains, ladino clover, etc.
• Wet
Yes: tall fescue, reed canarygrass,
timothy, p. ryegrass, b. trefoil, and
red clover
No: all the rest
Soil Conditions Affect Plants
• Low fertility
Yes: tall fescue, reed canarygrass,
orchardgrass, timothy,
lespedeza, red clover, b. trefoil
No: alfalfa, k. bluegrass, ladino clover
• Very acid (below 5.5)
Yes: birdsfoot trefoil, lespedeza
No: the rest
Herbicide Carryover
• Sites containing row crops pose a potential
threat with herbicide carryover that could
damage a new planting, or cover crop.
• Investigate, learn what herbicides were used;
if you can’t, use a cover crop tolerant of
carryover.
• Chemicals such as atrazine, Treflan, simazine,
Command, Pinnacle, Pursuit, and Sinbar all
have long residual periods.
Legumes
Alfalfa
• Perennial legume
• High nitrogen producer, over 80 lb/A
• Expensive to establish
- high fertility requirements
• Deep taproot, can be hard to kill
• Does not tolerate acidic, or wet soils
• Seedlings are not competitive
• Has some pest problems
Annual Sweetclover
• Annual legume
• Poor tolerance to cold
• Deep taproot
• Tremendous summer growth (6 ft. July)
• Seed in early May, rate 15 to 25 lb/A
• Needs pH above 6.0
• Excellent bee pasture (honey)
Austrian Winter Pea
• Winter annual legume
• Vine-like growth, similar to vetch
• High nitrogen producer, producing as
much as 90-150 lb/A
• Has some disease problems
• Seed at rate of 60-90 lb/A
Buckwheat
• Summer annual (broadleaf plant)
• Has no frost tolerance
• Tolerates wide range of soil conditions
• Grows rapidly, chokes out weeds
• Seed at a rate of 1 bushel/ A. from late
May - August
• Bushel weight 48 lb
Cowpea
• Summer annual legume
• Good short season green manure crop
• Good nitrogen “fixer”, 40 lb/A
• Seed at a rate of 30 - 40 lb/A
• Sow after the danger of frost has passed
• Cowpea mixed with
sorghum
Crimson Clover
• Winter annual Legume
• Adapted to light, well drained soils with
adequate pH (above 6.0)
• Beautiful color
• Good nitrogen producer 80 lb/A
• Seed 12 - 20 lb/A in late Aug. to mid-Sept.
• Susceptible to disease,especially if too much
fall growth accumulates
• Will winter kill if planted too late in fall
•
•
•
•
•
•
•
•
Flatpea
Long-lived perennial legume
Released as a conservation crop
Not recommended as a forage
Forms dense mat that is very competitive that
could suppress young trees and shrubs
Needs well drained soils and pH above 6.0
May need 2 - 3 years to become established
Requires specific inoculant; however garden
pea, sweetpea, and hairy vetch inoculant has
worked
Seed 20 - 30 lb/A with perennial grass in
spring or late summer
Hairy Vetch
• Winter annual legume
• Thick vines, climbing growth
• Great nitrogen producer, 100 lb/A
• Best suited to well drained soils
• Tolerates a wide range of pH
• Seed 25 - 40 lb/A in August
Hairy Vetch
Mix with
crimson clover
Mix with an annual cool
season tall-growing grass
Mammoth Red Clover
• Biennial legume
• Very good nitrogen producer, 80 lb/A
• Tolerant of moderate drainage
conditions, heavy soils, & pH above 5.5
• Tolerates competition
• Seed 8 - 15 lb/A, best seeded in spring
(late March to early May)
• Best grown for 1 year
Medium Red Clover
• Short-lived perennial legume
• Most common perennial legume in N.E.
• Very good nitrogen producer, 80 lb/A
• Seeding rate 10 - 15 lb/A
• Seed late March to early May, or midAugust to early September
White Clover
•
•
•
•
•
•
Perennial legume
Ladino clover is a medium to tall variety
Common clover is more low growing
Widely adapted, prefers higher pH 6.4
Long-lived with little maintenance
Not very competitive with grasses unless
managed
• Seed 5 - 7 lb/A, late March to early May
Yellow-Blossom Sweetclover
• Biennial legume
• Blooms in late spring
• Excellent bee pasture (honey)
• Deep, strong taproot
• Provides good weed control
(alleopathic)
• Will over-winter
• Seed 12 - 15 lb/A, in late April to early
May
Grasses
Annual Ryegrass
• Winter annual grass
(can establish itself through reseeding)
• Germinates quickly
• Vigorous, competitive
• Tolerates acidity (above 5.5), low fertility, and
poor drainage
• Forms dense cover, sod can create short term
planting problems
• Seed 25 - 32 lb/A, mid-Aug. to mid-Sept.
Barley
• Winter annual grass (small grain)
• Not as tall as other small grains, but
does produce an abundance of growth
• Not tolerant of wet soils, or late
planting (past mid-Oct. depending on
the season)
• Seed 48 - 96 lb/A, mid-Sept. to early
Oct.
• Bushel weight 48 lb
Cereal Rye
• Winter annual grass
• Grows rapidly in spring, deep rooted
• Very tolerant of low fertility and pH, does
respond to fertility
• Used as weed suppressing mulch
• Reported to have some alleopathy, could be a
problem with some small-seeded crops
• Most winter hardy of annual grasses
• Tall, stemmy, slow to breakdown
• Best at recovering (recycling nutrients)
• Seed 60 -120 lb/A, in late Sept. - late Nov.
Orchardgrass
• Long-lived perennial grass
• Competes will in mixture with other
grasses and legumes
• Excellent cover for wildlife
• Preferred conservation cover for fallow
fields, helps to keep weeds out of field
• Easy to establish
• Seed 25 - 35 lb/A alone, late Aug. to
early Sept., or mid-March to late April
Sorghum and Sudangrass
•
•
•
•
•
•
•
•
Summer annual grasses
Includes Sudex, sorghum x sudangrass
Tall growing, living mulch
Produces an abundance of dry matter
Growth can be tough to deal with
Has some alleopathic properties
Seed can contain some johnsongrass hybrids
Seed 30 - 40 lb/A after the danger of frost has
passed
Spring Oats
• Summer annual grass
• Used primarily as a companion crop
• Will out-compete weeds
• Great for quick growth
• Fall plantings have survived mild
winter
• Seed 32 - 64 lb/A mid-March thru April
• Bushel weight 32 lb
Timothy
• Perennial grass
• Least competitive of grasses, easily
choked out by competition
• Tolerant of low fertility, low pH, and
poorly drained soils
• Seed is very small, can easily be planted
too deep
• Seed 12 - 22 lb/A alone, late Aug. to
early October. Spring seeding risky.
Winter Wheat
• Winter annual grass
• Tall growing, living mulch
• Can produce an abundance of dry
matter
• Seed at a rate of 60 - 120 lb/A, from
October 5 to early November
• Bushel weight 60 lb
Grass/Legume Mixtures
• Perennial Seeding
medium red clover, or white clover
+
annual or perennial ryegrass, or
orchardgrass, or
timothy
Grass/Legume Mixtures
• Seeding for annual cover
spring oats + mammoth red clover
small grain + crimson clover
small grain + hairy vetch
barley + crimson clover
Agencies Who Can Help With
Cover Crops
• Maryland Department of Natural
Resources - MD DNR
• Natural Resources Conservation
Services - NRCS
• Maryland Department of Agriculture MDA
• Maryland Cooperative Extension - MCE
Resource Publication
• Managing Cover Crops Profitably
to order write:
Cover Crops Handbook
Sustainable Agriculture Publications
USDA
342 Aerospace Center
Washington, D.C. 20250-2200
Thank You