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of Field Crops | Appendices
811: Agronomy Guide > Forages
> Establishment (Planting)
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811: Agronomy Guide for Field Crops
When selecting a field, consider whether it is suitable for the
mixture you wish to plant. Limitations such as low pH, poor drainage
or weed problems such as quackgrass, should be corrected prior to
The most reliable time to seed forages is early spring, regardless
of whether the crop is direct-seeded or seeded with a companion
crop. With a spring seeding, moisture is usually adequate, and the
plants are well established for winter survival. Seed as early as
a seedbed can be prepared to increase the chances of adequate and
frequent rainfall during the critical germination period.
Summer seeding can be a viable alternative to spring seeding. A
summer seeding can typically follow winter or spring cereal harvest.
Companion crops are not recommended in summer seedings because they
compete too strongly for available soil moisture. Summer seedings
can work well on lighter soils but present a higher risk on heavier
Seeding too early in the summer increases the risk of hot, dry
conditions affecting germination and seedling development. Seeding
too late increases the chance of receiving a killing frost before
legume seedlings are adequately established and accumulate enough
root reserves to survive the winter. Legumes seeded in September
or October rarely survive the winter since small legume plants are
more susceptible to heaving. Even if these plants survive, they
will be slower starting and lower yielding. Alfalfa requires approximately
6 weeks of growth after germination to survive the winter. Alfalfa
will generally survive if the crown develops before a killing frost.
Summer-seed before the following dates:
- more than 3,100 CHUs - August 10-20
- 2,700 to 3,100 CHUs - August 1-10
- less than 2,700 CHUs - July 20-30
Birdsfoot trefoil has slow seedling development, so summer seedings
are usually unsuccessful. September seeding of straight grasses
may be successful, with the exception of reed canarygrass, which
is slow to establish.
Seed to soil contact is particularly important in dry summer conditions.
A loose, lumpy seedbed dries out quickly. Packing can help preserve
moisture. A fine seedbed can be more difficult to prepare in August
on clay loam soils, compared to loams, sandy loams and silt loams.
Avoid summer seeding on heavier soils that have a history of alfalfa
Winter annual weeds can be a common problem, and herbicide application
may be required. See OMAFRA
Publication 75, Guide to Weed Control. Be cautious to avoid
delaying growth due to a herbicide effect.
Table 3-4. Recommended Seeding Rates
for Legume and Pure Grass Stands and Approximate Seed/Weight of
Various Forage Species
|Pure Grass Species1
|Meadow & tall fescue
1For early seeding on a fine, firm seedbed, these rates
may be reduced by 25%, except where coated seed is being used.
2Use coated seed. Seed through the grain seed box.
Volunteer grain, because it may be thick and competitive, can be
a serious problem in summer seedings. Oat or barley will winterkill
in November, but winter wheat will be present until the first cut
the following year. Tillage can be used to reduce the problem of
volunteer cereals. There are herbicides that will kill volunteer
cereals, but forage grasses in the mixture will be stressed or may
also be killed.
No-till summer seeding can be successful if proper attention is
paid to residue management, seed placement and weed control. However,
using no-till to reseed an existing alfalfa field in August is not
recommended due to alfalfa autotoxicity (see Alfalfa
Autotoxicity), slugs and disease that may exist in the old sod.
Seeding Rates and Depth
The amount of seed recommended in Table
3-3, Recommended Forage Mixtures for Stored Feed and Pasture,
3-4, Recommended Seeding Rates for Legume and Pure Grass Stands
and Approximate Seeds/Weight of Various Forage Species, this
page, is intended for average to good conditions. Under excellent
management and favourable conditions for establishment, these rates
may be reduced by 25%. When coated seed is used, do not reduce these
rates, because coated seed contains fewer seeds per unit weight.
Do not expect very high seeding rates to compensate for poor conditions
(a rough seedbed, heavy companion crop, etc.).
Seed size can vary between varieties and between seed lots of the
same variety. Seeder calibration can help avoid over- or under-seeding.
See Table 3-4.
As a rule of thumb, seeding depth for most forages
should be 6-12 mm (1/41/2 in.) on clay and loam soils, and
12-18 mm (1/23/4 in.) on sandy soils.
Emergence declines rapidly if forage seeds are planted more than
20 mm (3/4 in.) deep. Legume seed on the soil surface may establish
if moisture conditions following seeding are ideal. Success of surface
seeding is much greater with late-March-to-early-April seedings
(including frost seeding) than in late-April or May.
The grain drill with a grass seed attachment is the most common
method of seeding forages. The standard grass seed box will handle
legume seeds and smaller grass seeds such as timothy and reed canarygrass.
Some drills have an additional seed box designed to seed coarser
grasses, such as bromegrass and orchardgrass, which do not flow
well through the standard box.
Most drills have drop pipes attached to the grass seed box. Where
fertilizer is applied through the grain drill, align the drop pipes
so that seed is dropped in a row over the fertilizer placed by the
disc opener. Drop the seed 25-35 cm (10-14 in.) behind the disc
opener to allow some soil to cover the fertilizer band before the
seed is dropped. This placement also ensures that the seed is not
planted too deep.
Packing the soil after planting can result in more even germination,
particularly during dry springs. Press wheels help cover the forage
seeds and firm the soil around the seed.
If press wheels are not available, a packer or rubber tire roller
pulled behind the drill to firm the soil have given satisfactory
results. A packer is not recommended if the soil is wet, particularly
on clay loam soils, where crusting can be a problem.
Packer seeders, such as Brillion seeders, can be used successfully
to seed forages. They are equipped with both fine and coarse seed
boxes. The first roller firms, levels and grooves the soil; the
seed is then dropped on this surface. The second roller covers the
seed with soil and firms it around the seed. This type of seeder
does an excellent job of controlling seed depth and firming the
seedbed. It does not apply fertilizer and thus does not produce
the starter effect achieved with the grain drill-band seeding method.
This is a disadvantage mainly at low and medium soil phosphorus
Broadcast seeders are also used for forages. Their main advantage
is increasing the speed of seeding. Control of seeding depth is
a problem and packing is necessary to cover the seed.
There are two types of broadcast seeders:
- Seeders that use spinners can give uneven distribution, particularly
under windy conditions or with seed mixtures containing light
and heavy seeds. This seeding method usually results in inferior
stands and is not recommended.
- Air-flow boom seeders overcome the problems of wind and seed
segregation while still permitting very rapid seeding.
This seeding system for forages can work well, but there have been
failures. To avoid stand failures, consider these guidelines:
- Ensure residue, including chaff, is evenly distributed.
- Eliminate perennial weeds, including quackgrass, before seeding.
Control annual weeds in new seedings.
- Plant no deeper than 18 mm (3/4 in.) on lighter soils or 12
mm (½ in.) on clay loam soils. Check that openers are placing
seed into the soil, rather than into surface residue.
- No-till spring seedings into soybean, cereal and corn residues
for the most reliable results. Remove straw from the previous
crop to improve seed placement.
- Kill the sod in the fall for fields where legumes will be no-till
spring-seeded. Avoid top growth of more than 15 cm (6 in.) at
spraying time to reduce the risk of insects, disease and alfalfa
autotoxicity (see Alfalfa Autotoxicity).
Seeding With a Companion Crop
Much of the forage acreage in Ontario is seeded under a companion
grain crop that suppresses annual grass weeds and gives fairly rapid
protection from erosion on rolling land. The disadvantage of a companion
crop is that it competes with the forages for moisture, light and
fertility. If any of these items are deficient, the forage seeding
will suffer before the grain crop does.
Harvesting the Companion Crop as Grain
This system of seeding provides a grain crop and a crop of straw
while the forage crop is being established. Competition from the
grain crop reduces forage establishment and subsequent yields, so
it is generally not recommended. Lodging of the companion crop or
delayed baling of straw can be risks to forage establishment. The
primary purpose of the seeding is to establish the forage, while
grain and straw production are of secondary importance.
- Oat, barley or mixed grains are commonly used as companion
crops. Spring wheat or spring triticale can also be used as a
companion crop and generally provide less competition to the forage
seeding. Six-row barley is preferable to two-row barley.
- As a general rule, select the strongest-strawed, shortest and
earliest grain variety in any species for the least competition.
- Reduce the spring grain seeding rate to 60-70 kg/ha.
- Reduce the nitrogen fertilizer or manure rate to minimize the
risk of a dense grain crop and lodging. Under most conditions,
do not apply more than 15 kg/ha of nitrogen on spring grains.
Harvesting the Companion Crop as Silage
Harvesting the grain crop as silage can eliminate some of the problems
associated with seeding forages under grain while still allowing
weed suppression and erosion control. The companion crop is removed
before it lodges or competes excessively for light and moisture.
Match the stage of cereal at cutting to the livestock nutritional
requirements. For high feed quality, cereals should be harvested
at the late-boot stage. Delaying harvest to the fully headed stage
will increase yield but reduce forage quality. The seeding rate
of the cereals and the nitrogen application may be the normal rates
in order to increase the silage yield. With reasonable soil moisture
following harvest, it is quite possible to also obtain a cut of
forage in late August in areas with 2,800 crop heat units or more.
Seeding forages without a companion crop removes the potential
threat to establishment from the grain crop. Under good management,
direct-seeded forage stands are often thicker and more uniform.
This is particularly true of forage species such as birdsfoot trefoil,
alfalfa and reed canarygrass, which do not tolerate heavy shade.
Since a grain crop is not competing for soil moisture, direct seedings
are less affected by June or July droughts.
Early-spring direct seedings can be expected to give one or two
cuts of forage in the seeding year, yielding 50%-60% of an established
stand. Direct-seeded forages are useful when the harvested forage
acreage must be increased on short notice to compensate for winterkill
or increased forage requirements.
Direct seedings have been most popular in Ontario:
- on silt loam, loam and sandy loam soils
- with birdsfoot trefoil- or alfalfa-based mixtures
- on dairy farms where nitrogen build-up from livestock manure
frequently results in cereal grain lodging
- where other crops provide the grain and straw requirements
Direct seedings have not met with success on all farms. Weed competition
is a greater problem with direct seeding than with under-seeding.
See Chapter 12, Weed
In the year of seeding, the root systems of forage crops are shallow
and more vulnerable to dry weather than established stands. Moisture
stress can reduce production to one cut rather than two but do not
usually reduce the stand.
Direct seedings on heavier clay loam soils require more skillful
seedbed preparation and seeding. Clay soils, particularly where
the seedbed is somewhat lumpy, are more vulnerable to dry conditions
during germination, thereby reducing establishment. They also are
more vulnerable to crusting and seedling emergence problems if heavy
rains follow seeding.
Seeding alfalfa after alfalfa is high risk because old stands of
alfalfa release a toxin that reduces germination, root development
and growth of new alfalfa seedlings. This is called autotoxicity.
Roots are swollen, curled, discoloured and lack root hairs. The
negative effects on root growth can significantly impact yields
for the life of the stand.
Reseeding alfalfa within 2-3 weeks of killing an old alfalfa stand
will result in reduced germination and thin stands. A longer delay
will allow full stand establishment, but because the toxins are
present for up to 6 months, the plants can suffer damage below ground
that will limit yields for the life of the stand. For maximum yields,
if the alfalfa is 2 or more years old, an intervening year of an
alternate crop is required before reseeding to alfalfa.
The toxins are not present the first year in new seedings, so seeding
failures or new seeds that were winterkilled can be reseeded without
an autotoxicity effect. This would include a summer seeding after
an unsuccessful spring seeding, or a spring seeding after an unsuccessful
It is not recommended that interseeding be done to thicken an established
alfalfa stand, as this is rarely successful. New seedlings often
germinate, look acceptable early and then die out over the summer.
Thin spots can sometimes be interseeded with red clover instead.
For normal growth, all legumes must have nitrogen-producing nodules
on their root systems. These nodules are produced by Rhizobium bacteria.
Legume species (alfalfa, clover, birdsfoot trefoil) require their
own specific strain of Rhizobium for proper nodulation. If a legume
is being planted for the first time in a field, the seed must be
inoculated with the proper strain of Rhizobium bacteria before planting.
Pre-inoculated seed is satisfactory, provided that the inoculant
is applied in the current season. Since the inoculant must be alive,
note the expiry date and handling precautions on the packet to ensure
effective nitrogen fixation. When a forage legume species has routinely
been grown in a field as part of the rotation, these bacteria are
usually present in the soil and should result in good nodulation.
The cost of the Rhizobia is low in comparison to the cost of seed.
If there is any doubt about the presence of Rhizobia in the soil,
the seed should be inoculated.
Table 3-5. General Nitrogen Recommendations
- Perennial Forages
|Legume or legume-grass at seeding
|Without a nurse crop
|With a nurse crop
|Grass for seed
|Hay or pasture
|Half or more legumes
|Grass (less than one-third legumes)