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OATS
Avena sativa
Also called: spring oats
Type: cool season annual cereal
Roles: suppress weeds, prevent erosion, scavenge
excess nutrients, add biomass, nurse crop
Mix with: clover, pea, vetch, other legumes or other
small grains
See charts, pp. 66 to 72, for ranking and management summary.
If you need a low-cost, reliable fall cover that winterkills in Hardiness
Zone 6 and colder and much of Zone 7, look no further. Oats provide
quick, weed-suppressing biomass, take up excess soil nutrients and
can improve the productivity of legumes when planted in mixtures.
The cover’s fibrous root system also holds soil during cool-weather
gaps in rotations, and the ground cover provides a mellow mulch before
low-till or no-till crops.
An upright, annual grass, oats thrive under cool, moist conditions
on well-drained soil. Plants can reach heights in excess of 4 feet.
Stands generally fare poorly in hot, dry weather.
BENEFITS
You can depend on oats as a versatile, quick-growing cover for
many benefits:
Affordable biomass. With good growing conditions
and sound management (including timely planting), expect 2,000 to
4,000 pounds of dry matter per acre from late-summer/early fall-seeded
oats and up to 8,000 pounds per acre from spring stands.
Nutrient catch crop. Oats take up excess N and
small amounts of P and K when planted early enough. Late-summer
plantings can absorb as much as 77 lb. N/A in an eight- to ten-week
period, studies in the Northeast and Midwest have shown (313,
329).
Where the plant winterkills, some farmers use oats as a nitrogen
catch crop after summer legume plowdowns, to hold some N over winter
without needing to kill the cover in spring. Some of the N in the
winterkilled oats may still be lost by spring, either through denitrification
into the atmosphere or by leaching from the soil profile. Consider
mixing oats with an overwintering legume if your objective is to
maximize N contribution to the next crop.
Smother crop. Quick to germinate, oats are a great
smother crop that outcompetes weeds and also provides allelopathic
residue that can hinder germination of many weeds—and some
crops (see below)—for a few weeks. Reduce crop suppression
concerns by waiting two- to three weeks after killing oats before
planting a subsequent crop.
Fall legume nurse crop. Oats have few equals as
a legume nurse crop or companion crop. They can increase the fertilizer
replacement value of legumes. Adding about 35 to 75 lb. oats/a to
the seeding mix helps slow-establishing legumes such as hairy vetch,
clovers or winter peas, while increasing biomass. It also helps
reduce fall weeds. The oats will winterkill in many areas while
improving the legume’s winter survival.
Spring green manure or companion crop. Spring
-seeded with a legume, oats can provide hay or grain and excellent
straw in the Northern U.S., while the legume remains as a summer—or
even later—cover. There’s also a haylage option with
a fast-growing legume if you harvest when oats are in the dough
stage. The oats will increase the dry matter yield and boost the
total protein, but, because of its relatively high nitrogen content,
could pose a nitrate-poisoning threat to livestock, especially if
you delay harvesting until oats are nearing the flowering stage.
The climbing growth habit of some viny legumes such as vetch can
contribute to lodging and make oat grain harvest difficult. If you’re
growing the legume for seed, the oats can serve as a natural trellis
that eases combining.
MANAGEMENT
Establishment & Fieldwork
Time seeding to allow at least six to 10 weeks of cool-season growth.
Moderately fertile soil gives the best stands.
Late-summer/early-fall planting. For a winterkilled
cover, spring oats usually are seeded in late summer or early fall
in Zone 7 or colder. Broadcasting or overseeding will give the best
results for the least cost, unless seeding into heavy residue. Cleaned,
bin-run seed will suffice.
If broadcasting and you want a thick winterkilled mulch, seed at
the highest locally recommended rate (probably 3 to 4 bushels per
acre) at least 40 to 60 days before your area ’s first killing
frost. Assuming adequate moisture for quick germination, the stand
should provide some soil-protecting, weed-suppressing mulch.
Disk lightly to incorporate. In many regions, you’ll have
the option of letting it winterkill or sending in cattle for some
fall grazing.
If seeding oats as a fall nurse crop for a legume, a low rate (1
to 2 bushels per acre) works well.
If drilling oats, seed at 2 to 3 bushels per acre 1/2 to 1 inch
deep, or 1 1/2 inches when growing grain you plan to harrow for
weed control.
Shallow seeding in moist soil provides rapid emergence and reduces
incidence of root rot disease.
Timing is critical when you want plenty of biomass or a thick ground
cover. As a winter cover following soybeans in the Northeast or
Midwest, overseeding spring oats at the leaf-yellowing or early
leaf-drop stage (and with little residue present) can give a combined
ground cover as high as 80 percent through early winter (200).
If you wait until closer to or after soybean harvest, however, you’ll
obtain much less oat biomass to help retain bean residue, Iowa and
Pennsylvania studies have shown.
Delaying planting by as little as two weeks in late summer also
can reduce the cover’s effectiveness as a spring weed fighter,
a study in upstate New York showed. By spring, oat plots that had
been planted on August 25 had 39 percent fewer weed plants and one-seventh
the weed biomass of control plots with no oat cover, while oats
planted two weeks later had just 10 percent fewer weed plants in
spring and 81 percent of the weed biomass of control plots (329,
330).
No-hassle fieldwork. As a winterkilled cover,
just light disking in spring will break up the brittle oat residue.
That exposes enough soil for warming and timely planting. Or, no-till
directly into the mulch, as the residue will decompose readily early
in the season.
Winter planting. As a fall or winter cover crop
in Zone 8 or warmer, seed oats at low to medium rates. You can kill
winter-planted oats with spring plowing, or with herbicides in reduced-tillage
systems.
Spring planting. Seeding rate depends on your
intended use: medium to high rates for a spring green manure and
weed suppressor, low rates for mixtures or as a legume companion
crop. Higher rates may be needed for wet soils or thicker ground
cover. Excessive fertility can encourage lodging, but if you’re
growing oats just for its cover value, that can be an added benefit
for weed suppression and moisture conservation.
Easy to kill. Oats will winterkill in most of
zone 7 or colder. Otherwise, kill by mowing or spraying soon after
the vegetative stage, such as the milk or soft dough stage. In no-till
systems, rolling/crimping will also work (best at dough stage or
later). See Cover
Crop Roller Design Holds Promise For No-Tillers. If speed of
spring soil-warming is not an issue, you can spray or mow the oats
and leave on the soil surface for mulch.
If you want to incorporate the stand, allow at least two to three
weeks before planting the next crop.
Killing too early reduces the biomass potential and you could see
some regrowth if killing mechanically. But waiting too long could
make tillage of the heavier growth more difficult in a conventional
tillage system and could deplete soil moisture needed for the next
crop. Timely killing also is important because mature oat stands
can tie up nitrogen.
Oats, Rye Feed Soil in Corn/Bean Rotation
Bryan and Donna Davis like what cover crops
have done for their corn/soybean rotation. They use less grass
herbicide, have applied insecticides only once in the last
six years, and they have seen organic matter content almost
double from less than 2% to almost 4%.
Rye and oats are the cover crop mainstays on
the nearly 1,000 acres they farm near Grinnell, Iowa. Bryan
and Donna purchased the farm—in the family since 1929—in
1987 and almost immediately put most of the operation under
100% no-till, a system they had experimented with over the
years. They now till some acres and are also in the process
of transitioning 300 acres to organic.
Moving 1/3 of their acreage toward organic seems
the logical culmination of the Davis’ makeover of their
farm that started with a desire to “get away from the
chemicals.” That was what motivated them to start using
cover crops to feed the soil and help manage pests.
“We were trying to get away from the idea
that every bug and weed must be exterminated. Rather, we need
to ‘manage’ the system and tolerate some weed
and insect pressure. It should be more of a balance,”
says Bryan.
Bryan and Donna are practitioners and proponents
of “biological farming,” a systems approach based
on such principles as feeding the soil to keep it biologically
active, reducing chemical inputs and paying attention to trace
elements or micronutrients in order to maintain balance in
the system. Cover crops play an integral role in this system.
They seed oats at 2-3 bu/A in spring or fall,
depending on time and labor availability. Donna does most
of the combining and planting, but even with a lot of acres
for two people to manage, cover crops are a high priority
on their schedule. Fall-seeded oats are planted after soybean
harvest and “need rain on them soon after planting to
get them started.” They’ll put on about a foot
of growth before winterkilling, usually in December in their
south-central Iowa conditions.
Spring oats are broadcast in mid or late March
with a fertilizer cart and then rotary harrowed. If going
back to corn, they seed at a heavier, 3.5 bu rate, expecting
only about 5 or 6 weeks of growth before they work down the
cover crop with a soil finisher and plant corn in early May.
For soybeans, they either kill chemically and no-till the
beans, or work down and seed conventionally.
They have managed rye in different ways over
the years depending on its place in the rotation, but prefer
to seed into killed or tilled rye rather than a living cover
crop. They figure that they get about 35 lb. N from oats and
up to 60 lb. from rye.
On their organic transition acres they are applying
chicken manure (2 tons/A), and cover crops are crucial to
sopping up excess nutrients and crowding out the weeds that
crop up in response to the extra nutrients. They feel that
their efforts to balance nutrients are also helping with weed
control, because weeds feed on nutrient imbalances.
In addition to the increase in soil organic
matter, attributed to cover crops and no-tillage, they’ve
also seen improvements in soil moisture and infiltration.
Fields that used to pond after heavy rains no longer do. Soybeans
are weathering drought better, and corn stays green longer
during a “more natural” drying down process.
“Our system takes more time and is more
labor intensive, but if you look at the whole budget, we are
doing much better now. We have cut our chemical costs dramatically,
and have reduced fertility costs—in some fields—by
1/3 to 1/2” says Bryan. “With energy costs these
days, you can’t afford not to do this.”
Davis is careful to note that this is not just
about adding one component such as cover crops. “You
need to address the whole system, not just one piece of the
pie. To be able to have a sustaining system, you must work
with the living system. Feed the soil and give it a roof over
its head.” Cover crops play a crucial role in that system.
—Andy Clark |
Pest Management
Allelopathic (naturally occurring herbicidal)
compounds in oat roots and residue can hinder weed growth for a
few weeks. These compounds also can slow germination or root growth
of some subsequent crops, such as lettuce, cress, timothy, rice,
wheat and peas. Minimize this effect by waiting three weeks after
oat killing before seeding a susceptible crop, or by following with
an alternate crop. Rotary hoeing or other pre-emerge mechanical
weeding of solo-seeded oats can improve annual broadleaf control.
Oats are less prone to insect problems than wheat
or barley. If you’re growing oats for grain or forage, armyworms,
various grain aphids and mites, wireworms, cutworms, thrips, leafhoppers,
grubs and billbugs could present occasional problems.
Resistant oat varieties can minimize rusts, smuts
and blights if they are a concern in your area or for your cropping
system. Cover crops such as oats help reduce root-knot nematodes
and vegetable crop diseases caused by Rhizoctonia, results
of a producer study in South Carolina show (448),
although brassicas are better. To reduce harmful nematodes that
oats could encourage, avoid planting oats two years in a row or
after nematode-susceptible small grains such as wheat, rye or triticale
(71).
Other Options
There are many low-cost, regionally adapted and widely available
oat varieties, so you have hay, straw, forage or grain options.
Select for cultural and local considerations that best fit your
intended uses. Day-length, stalk height, resistance to disease,
dry matter yield, grain test weight and other traits may be important
considerations. In the Deep South, fast-growing black oats (Avena
strigosa) look promising as a weed-suppressive cover for soybeans.
See Up-and-Coming Cover
Crops.
Aside from their value as a cover crop, oats are a great feed supplement,
says grain and hog farmer Carmen Fernholz, Madison, Minn. A niche
market for organic oats also could exist in your area, he observes.
Oats are more palatable than rye and easily overgrazed. If using
controlled grazing in oat stands, watch for high protein levels,
which can vary from 12 to 25 percent (434).
The potassium level of oat hay also is sometimes very high and could
cause metabolic problems in milking cows if it’s the primary
forage. Underseeding a legume enhances the forage option for oats
by increasing the biomass (compared with solo-cropped oats) and
providing nitrogen for a subsequent crop.
COMPARATIVE NOTES
 Fall
brassicas grow faster, accumulate more N and may suppress weeds,
nematodes and disease better than oats.
Rye
grows more in fall and early spring, absorbs more N and matures
faster, but is harder to establish, to kill and to till than oats.
As a
legume companion/nurse crop, oats outperform most varieties of
other cereal grains.
Oats
are more tolerant of wet soil than is barley, but require more
moisture. Seed sources. See Seed Suppliers.
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