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Forages: Tillage & Establishment
Excerpt from Agronomy Guide for Field Crops (Chapter 5)Order OMAFRA Publication 811: Agronomy Guide for Field CropsTable of Content
Seedbed PreparationThe goal of tillage is threefold:
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 emergence of young seedlings
difficult. Soil should be firm enough at planting for a footprint
to sink no deeper than 9 mm Heavier soils plowed in the spring often require excessive tillage to produce a fine seedbed. If soils are worked too fine, a surface crust could reduce emergence after a heavy rainfall, while also increasing erosion potential and decreasing water infiltration. No-till seeding of forages has been quite successful where the soil conditions following the previous crop were smooth and level. The biggest risk factor to no-till seeding of forages is slug damage where surface residue is heavy. 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. When selecting a field, consider whether it is suitable for the mixture you wish to plant. If there are limitations such as low pH, poor drainage or weed problems, such as quackgrass, these should be corrected prior to seeding. | Top of Page | Seeding TimeSpring SeedingThe most reliable time to seed forages is early spring, regardless of whether the crop is direct-seeded or under 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 moisture during the critical germination period. Summer SeedingSummer 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. Important considerations for successful summer seeding are: | seeding date | seedbed preparation | heaving | weed control | volunteer grain | no-till | Seeding DateSeeding too early in the summer increases the risk of hot, dry conditions during germination and seedling development. Seeding too late increases the chance of freeze-up 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. Alfalfa needs approximately 6 weeks' growth after germination to survive the winter and will generally survive if the crown develops before a killing frost. Small legume plants are more susceptible to winter heaving. Even if these plants survive, they will be slower starting and lower yielding. Summer seeding should take place before the following dates:
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, as it is slow to establish and should not be summer seeded. Seedbed PreparationSeed 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. HeavingAvoid summer seeding on heavier soils that have a history of alfalfa heaving. Weed ControlWinter annual weeds can be a common problem, and herbicide application may be required. Refer to OMAFRA Publication 75, Guide to Weed Control. Caution must be used to avoid delaying growth due to a herbicide effect. (Order OMAFRA Publication 75, Guide to Weed Control) Volunteer GrainVolunteer grain, because it may be thick and competitive, can be a serious problem in summer seedings. Oats 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, slugs and disease that may exist in the old sod. | Top of Page | Seeding Rates and DepthThe amount of seed recommended in Table 5-3, Recommended Forage Mixtures for Stored Feed and Pasture and Table 5-4, Recommended Seeding Rates for Pure Grass Stands is intended for average to good conditions. | Top of Page | 1For early seeding
on a fine, firm seedbed, these rates may be reduced by 25%, except
where coated seed is being used. 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 5-5, Approximate Seeds per Kilogram of Various Forage Species. | Top of Page | 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. Percentage 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 than in late April or May. | Top of Page | Seeding Equipment| Grain Drill | Packer Seeders | Broadcast Seeders | No-Till Drills | Grain DrillThe grain drill with a grass seed attachment is a very satisfactory 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. Align the drop pipes so that seed is dropped in a row over the fertilizer placed by the disc opener. The seed should be dropped 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 a 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, very satisfactory results can be obtained by pulling a packer or rubber tire roller behind the drill to firm the soil. Do not use a packer if the soil is wet, particularly on clay loam soils, where crusting can be a problem. | Top of Page | Packer SeedersPacker seeders, such as Brillion seeders, can be successfully used to seed forages and are equipped with both fine and coarse seed boxes. The first roller firms, levels and grooves the soil, and 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 levels. | Top of Page | Broadcast SeedersBroadcast seeders are also used to seed forages. Their main advantage is speed of seeding. There are two types of broadcast seeders and with both, control of seeding depth is a problem. Packing is necessary to cover the seed. 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. | Top of Page | No-Till DrillsThis seeding system for forages can work well, but in some situations can fail. To avoid stand failures, follow these guidelines:
| Top of Page | Seeding With a Companion CropMuch 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. | Top of Page | Harvesting the Companion Crop as GrainThis system of seeding provides a grain crop and a crop of straw while the forage crop is being established. Competition from the grain crop can reduce forage establishment and subsequent yields. Lodging of the companion crop due to excess nitrogen can be a real threat to forage establishment. One should recognize that the primary purpose of the seeding is to establish the forage, while grain and straw production are of secondary importance. Recommended guidelines:
| Top of Page | Harvesting the Companion Crop as SilageSome of the problems associated with seeding under grain can be eliminated by harvesting the grain crop as silage. Match stage of cutting to 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. Harvesting the companion crop as silage allows weed suppression and erosion control, but the companion crop is removed before it lodges or competes excessively for light and moisture. In this situation, both the seeding rate of the cereals and the nitrogen application may be the normal rate 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 2,600 heat units or more. | Top of Page | Direct SeedingSeeding 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:
Direct seedings have not met with success on all farms. Weed competition is a greater problem with direct seeding than with under-seeding. (see the section Weed Control). In the year of seeding, the root systems of forage crops are shallow and therefore more vulnerable to drought than established stands. Droughts 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. | Top of Page | Alfalfa AutotoxicitySeeding 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. Germination and establishment problems (plant density) result when the existing stand is not killed at least 2 or 3 weeks before reseeding. More importantly, these toxins are present for up to 6 months, which are sufficient to permanently reduce new stand yields. 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. | Top of Page | InoculationFor 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. | Top of Page | Updates on Forages: Tillage & EstablishmentNo updates available at this time. | Top of Page | Related links...| Top of Page | For more information:Toll Free: 1-877-424-1300 Local: (519) 826-4047 E-mail: ag.info.omafra@ontario.ca |
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