Successful Forage Establishment
A successful forage establishment is a uniform, weed free stand that will grow quickly and vigorously to provide high yields during that first year, and for the life of the stand. The most critical factors include packing a firm seedbed and proper seed placement.
The goals of forage seedbed preparation are to:
produce a fine, firm, level seedbed that allows good control of uniform seeding depth,
leave a well packed seedbed with good seed-to-soil contact,
eliminate residue that may harm establishment, and
produce a smooth surface for future harvesting operations.
Forage seed is very small, making good seed-to-soil contact essential for germination, particularly in dry conditions. A loose, lumpy seedbed dries out quickly, and lumps make the uniform emergence of young seedlings difficult. A firm, level, clod-free seedbed is very important for uniform seeding depth and good seed-to-soil contact. Avoid creating a soft, fluffy seedbed by deep tillage. Using a spike-tooth harrow before the drill loosens the soil rather than packs it. Soil should be firm enough at planting for a footprint to sink no deeper than 9 mm (3⁄8 in.). If necessary, pack before seeding in addition to packing after the drill. Ideally, forage seedlings should be able to emerge without a rainfall.
Many farmers seed alfalfa-grass mixtures in the 16 – 20 lbs/acre range. Lower rates may work under optimal conditions, but are higher risk under adverse weather conditions following seeding. Higher seeding rates provide faster initial ground cover to provide more competitiveness with weed seedlings. Research has also shown higher alfalfa seeding rates result in less mature, finer stemmed alfalfa plants. (http://bit.ly/1kSmyAT) Seed size can vary between varieties and between seed lots of the same variety. Seeder calibration will help avoid over- or under-seeding.
Use proven certified varieties rather than unknown brands or common seed to ensure higher germination and purity, and provide better yield, persistence, disease resistance and appropriate maturity. Using cheap seed can result in very significant yield losses and increased risk over the life of a stand, making it very expensive.
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 significantly 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.
1. Grain Drill
The grain drill with a small (or fine) seed attachment is still a common method of seeding forages. The standard small seed box will handle legume seeds and smaller grass seeds, such as timothy and reed canarygrass, and low amounts of orchardgrass, tall fescue, meadow fescue, and festuolium. Some drills have an additional large (or coarse) forage seed box with an agitator that is designed to seed larger fluffier seed, such as bromegrass and other grasses, that do not flow well through the standard box. Rows should be no more than 18 cm (7 inches) wide.
When seeding forage using most conventional grain drills, there should be 4-5 alfalfa seeds/ square foot visible on the soil surface, otherwise the placement may be too deep.
Where starter phosphate fertilizer can be applied through the drill, align the drop pipes so that seed is dropped in a row over the fertilizer placed by the disc opener. Drop the seed behind the disc opener to allow some soil to cover the fertilizer band before the seed is dropped. Starter fertilizer provides an advantage mainly where soil phosphorus fertility levels are low to medium.
Packing the soil after planting results in more rapid and even germination, particularly during dry weather and on lighter soils. Where seedlings are seen emerging first in tire tracks and headlands, this indicates insufficient packing was done. If necessary, pack before seeding in addition to packing after the drill. Drill press wheels help cover the forage seeds and firm the soil around the seed. Alternately, a packer can be pulled behind the drill, or pack as soon as possible after seeding to prevent excessive moisture loss. Sprocket packers are preferable over smooth rollers to avoid potential crusting and to push any seed on the surface into the soil. Packing is not advised if the soil is wet, particularly on heavier soils, where compaction and crusting can be problems.
2. Packer Seeders
Packer seeders, such as Brillion seeders, can be used successfully to seed forages. They are usually equipped with both small (fine) and large (coarse) seed boxes, and two rollers. 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. Packer seeders do an excellent job of controlling seed depth and firming the seedbed. Packer seeders do not work as well on very hard ground or on a sandy soil. Also, they cannot band apply starter fertilizer similar to some drills.
3. Broadcast Seeders
Broadcast seeders main advantage is increasing the speed and capacity of seeding. Control of seeding depth is a potential problem and packing is necessary to cover the seed. Sprocket packers are preferred over smooth rollers to push surface seed into the soil.
There are two types of broadcast seeders:
Seeders that use “spinner spreaders” can give uneven distribution, particularly under windy conditions or with seed mixtures containing light and heavy seeds. This seeding method often results in inferior stands.
“Air-flow boom seeders” overcome the problems of wind, seed segregation and spread pattern, while still permitting very rapid seeding. Another method successfully used by farmers mixes the forage seed with MAP for immediate application using an air-flow fertilizer spreader.
4. No-Till Drills
No-till seeding of forages has been quite successful where the soil conditions following the previous crop were smooth and level. Weed control and proper seed placement utilizing depth control and packing wheels are important. Where surface residue is heavy, slug damage to forage seedlings is a risk. Land susceptible to erosion will benefit from increased surface residue. However, seeding equipment must be able to handle the increased residue left by reduced tillage systems without compromising seed placement and adequate seed-to-soil contact. When the soil is too wet, the no-till seed furrow may not close properly, and poor seed-to-soil contact results.
Consider these guidelines when no-tilling forage seedings:
Eliminate perennial weeds, including quackgrass, and winter annual weeds before seeding. Control broadleaf annual weeds with a herbicide in new seedings.
Ensure residue from the previous crop is evenly distributed. Manage any excessive residue to improve seed placement and to prevent slug damage. No-till spring seedings into soybean, cereal and corn silage stubble provide the most reliable results.
Seeding depth 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. Check that openers are placing seed into the soil, rather than into surface residue.
Direct Seeding Or Seeding With A Companion Crop?
Companion crops are sometimes also referred to as “nurse crops”. Forage seeding under a companion spring cereal crop (oats, triticale, barley, wheat) can suppress annual grass weeds and provide rapid protection from erosion on sloping 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 cereal crop does. Direct-seeded forage stands are often thicker and more uniform, particularly with alfalfa, birdsfoot trefoil, and reed canarygrass, which do not tolerate heavy shading.
1. Direct Seedings
Early-spring direct seedings can usually be expected to provide 2 cuts (or possibly 3) of forage in the seeding year, yielding 50 – 65% of an established stand. Under good conditions, first-cut can be harvested 60 – 70 days after seeding.
Direct seedings are more common where:
fields have a lower risk of soil erosion,
good drainage facilitates early spring seeding,
weed control within the crop rotation is good, and
on some dairy farms where uniformly high nutrient quality haylage is required.
Direct seedings have not met with success on all farms. Weed competition can be a greater problem with direct seeding than with companion crop under-seeding. A cereal companion crop can provide some early protection to fields that have greater risk of erosion during the initial establishment period, including lighter soil types with slope. Direct seedings on heavier clay loam soils can require more skillful seedbed preparation and seeding. Direct seedings on clay soils are more vulnerable to crusting and seedling emergence problems if heavy rains follow seeding.
2. Harvesting The Companion Crop As Silage
Harvesting the companion cereal crop by combining it as grain is not a preferred practice because it usually reduces the establishment of the forage crop for the life of the stand. Harvesting the cereal crop at the boot-stage as haylage or baleage reduces the competition, enabling better forage establishment while still allowing weed suppression and erosion control, and providing additional forage. The companion crop is removed before it lodges or competes excessively for light and moisture. If the cereal crop is cut and lies in the swath for an extended period while wilting it has the potential to damage the new forage seeding.
Although some farmers use a full cereal seeding rate and apply nitrogen to maximize forage yield, the heavier growth increases the risk to successful forage establishment. Seeding at reduced rates (50%) and avoiding N application usually improves the forage establishment.
Oats are the preferred forage cereal by many farmers, but barley, triticale and spring wheat are other options. Although oat rust is a potential concern, forage oats tend to out-yield barley (especially in poorer conditions and later seedings), with less cereal regrowth and heading in the second-cut, and without the awns. Peas are sometimes added to the cereals in a mixture to improve forage nutrient quality. This eliminates having the option of herbicide weed control if required and can increase the risk of extended wilting that may damage the forage seeding.
Cereals can reach the boot stage in as early as 60 days or less, so if seeded before the first week of May they could be harvested in late-June or early-July. With reasonable soil moisture following harvest, it is quite possible to obtain another cut of forage during August in most areas. (Forage Production From Spring Cereals and Cereal-Pea Mixtures www.omafra.gov.on.ca/english/crops/facts/98-041.htm)
The most reliable time to seed forages is early spring. Seed as early as a seedbed can be properly prepared to increase the chances of adequate moisture during the critical germination and early growth period. The approximate optimal time in most of southern Ontario is before May 7th. Seedings completed in late-May and June are usually much less successful.
Summer seeding can be a viable alternative to spring seeding. It has the advantage of providing a full yield potential the following year. A summer seeding typically follows winter or spring cereal harvest, so volunteer cereal must be controlled in a timely manner. Companion crops are not recommended in summer seedings. For optimal summer seeding dates and other information, refer to “Summer Seeding Alfalfa” (www.qualityseeds.ca/blog/2-summer-seeding-alfalfa).
Legume species (alfalfa, clover, birdsfoot trefoil) require their own specific strain of Rhizobium for proper nodulation. While many soils contain some rhizobia from previous crops, not all have adequate amounts. 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. Most alfalfa seed is already pre-inoculated.
Fertility and pH
Suggested phosphate and potash rates for new seedings are provided in Table 3–7, Phosphate Recommendations for Forages, and Table 3–8, Potash Requirements for Forages of the OMAFRA Publication 811, Agronomy Guide For Field Crops. (www.omafra.gov.on.ca/english/crops/pub811/3fertility.htm)
When direct-seeding on soils that require phosphate fertilizer, establishment can be improved by band placement of MAP starter fertilizer, ideally 2.5 cm (1 inch) below the seed. Additional fertilizer required can be broadcast and incorporated before seeding. If sulphur is required, sulphate can be applied at establishment or elemental sulphur applied the previous year. (Sulphur On Alfalfa www.qualityseeds.ca/blog/7-sulphur-on-alfalfa)
Legumes are generally not tolerant of acid soil conditions, especially alfalfa. Low pH results in poor germination, slow seedling growth, poor Rhizobium nodulation and subsequent low yields. Lime fields for alfalfa to a pH of at least 6.7. Lime reacts slowly with acid soils, so they should be limed and incorporated 1 year before seeding at rates indicated by soil tests.
Perennial weeds should be eliminated before seeding. Herbicide control of broadleaf annual weeds at establishment is especially important in direct seedings. Determine the optimum time of spraying by the stage of development of the new seeding. The risk of injury to alfalfa seedlings is greatly increased when 2,4-DB application is made outside of the first- to the third-trifoliate stage window. Uniform emergence as a result of good seedbed preparation and packing make it easier to stage. Target the first-trifoliate stage, where weeds are smaller and easier to control. 2,4-DB can suppress legume growth for a period of 2 – 3 weeks and severe injury can occur under drought or high temperatures. Grower experience has been that injury to seedling alfalfa plants can be minimized when reducing the lowest labelled rate of 2,4-DB by 25%. A reduced rate may reduce the level of weed control. MCPA can be added to 2,4-DB where mustard is a problem. Refer to OMAFRA Publication 75, Guide To Weed Control.
Watch For Potato Leafhopper (PLH)
New alfalfa seedings are very susceptible to PLH damage, including resistant varieties. PLH feeding causes reduced stem elongation, reduced root development, leaf damage, decreased vigour, and stunting. PLH damage in new seedings will permanently reduce yields for the life of the stand. Be prepared to apply an insecticide when PLH exceed threshold levels. (Potato Leafhopper In Alfalfa www.qualityseeds.ca/blog/19-quality-time-with-joel)
New forage seeding crop insurance is an inexpensive way to manage the risk of unsuccessful establishment due to adverse weather. In Ontario, contact Agricorp at 1-888-247-4999 (www.bit.ly/1EWmkes).