Forages: Establishment (Planting)

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Pub 811: Agronomy Guide > Forages > Establishment (Planting)

Excerpt from Agronomy Guide for Field Crops
Order OMAFRA Publication 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 seeding.

• Seeding Time
• Table 3-4. Recommended Seeding Rates for Legume and Pure Grass Stands and Apprxoimate Seeds/Weight of Various Forage Species
• Seeding Rates and Depth
• Seeding Equipment
• Seeding with a Companion Crop
• Direct Seeding
• Alfalfa Autotoxicity
• Inoculation
  • Table 3-5. General Nitrogen Recommendations - Perennial Forages

Seeding Time

Spring Seeding

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

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 soils.

Seeding Date

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.

Seedbed Preparation

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.

Heaving

Avoid summer seeding on heavier soils that have a history of alfalfa heaving.

Weed Control

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.

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

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

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, and Table 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 (1/4—1/2 in.) on clay and loam soils, and 12-18 mm (1/2—3/4 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.

Seeding Equipment

Grain Drill

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

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 fertility levels.

Broadcast Seeders

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.

No-Till Drills

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.

Recommended Guidelines

• 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.

Direct Seeding

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 Control.

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.

Alfalfa Autotoxicity

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 summer seeding.

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.

Inoculation

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.