Summer Seeding Forages?

The most reliable time to seed forages is in the spring. With an April or early May seeding, moisture is usually adequate and the legumes are well established for winter survival. However, spring seeding is not always possible due to a number of factors, including wet field conditions.

Summer seeding of alfalfa forage mixtures can be a viable alternative to spring seeding. Fields seeded this summer can be treated as established stands next year with full yield potential. Do not use companion crops with summer seedings. They compete too strongly for available soil moisture, and will reduce stand establishment.

The following are some points to consider regarding successful summer seeding of forages:

Seeding Date

There are two critical risks associated with summer seeding alfalfa. Seeding too early in the summer increases the risk of dry conditions during germination and seedling development. Summer seedings fail if seeds germinate and then starve for moisture. Seeding too late increases the chance of freeze-up before the alfalfa seedlings are adequately established. Seeding must be early enough to allow the alfalfa to accumulate sufficient root reserves to survive the winter.

Alfalfa needs about 6 weeks of growth after germination to survive the winter, and will survive best if the crown develops before a killing frost. Recommended summer seeding dates are:

• > 2900 CHU areas - August 10^th - 20^th
• 2500 - 2900 CHU areas - August 1^st - 10^th
• < 2500 CHU areas- July 20^th - 30^th.

Lack of moisture for adequate germination is always a risk. If soil conditions are extremely dry, and no rain is in the forecast, abandon the plans for summer seeding.

Most grass species can be successfully seeded up to 2 or 3 weeks later than alfalfa. Birdsfoot trefoil and reed canarygrass have slow seedling development, so summer seedings of these species are rarely successful.

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Seedbed Preparation

Seed to soil contact is important for germination, particularly in dry summer conditions. A loose, lumpy seedbed dries out quickly. A fine, firm seedbed is a necessity. Soil should be firm enough at planting for a footprint to sink no deeper than 3/8 inch. Packing before seeding can help. Seed shallow (¼ inch). Always pack the soil after seeding.

Heaving

Summer seedings are more prone to heaving in late winter, especially if root development was limited due to slow germination or cool fall weather. Avoid summer seeding on heavier soils that have a history of alfalfa heaving.

Weed Control

Winter annual weeds like pennycress and shepherd's purse are a common problem. It is not unusual to have to spray early August seedings. If warranted, a low rate of 2,4-DB and MCPA can be used for broadleaf weed control, but be sure that the alfalfa is in the 1 to 4 trifoliate stage. Caution must be used to avoid delaying growth due to the herbicide effect. Refer to OMAFRA Publication 75 "Guide To Weed Control". If these weeds are not controlled, they will show up in the first cut next spring, but should not be a problem after that. Annual grass and broadleaf weeds will be killed by fall frosts. Perennials, such as quackgrass, must be controlled before seeding.

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Volunteer Grain

Competition from volunteer grain can be a serious problem. Tillage can reduce the problem. If there is enough moisture, a light cultivation will prompt the grain to germinate. A second cultivation 10 days later will destroy much of this grain. Moldboard plowing to bury the grain is more effective than disking, but may dry the soil out too much. In pure alfalfa stands, a grass herbicide can be used.

Alfalfa Following Alfalfa

Seeding alfalfa after alfalfa is high risk! Old stands of alfalfa release a toxin that reduces the germination and growth of new alfalfa seedlings. This is termed alfalfa "autotoxicity". Establishment problems can result if the existing stand was not plowed or sprayed at least 3 weeks before reseeding. These toxins are present for up to 6 months, sufficient to permanently reduce new stand yields. For maximum yields, one year of an alternate crop is required. The toxins are not present the first year in new seedings, so seeding failures can be reseeded without an autotoxicity effect.

Summer seeding of alfalfa is an alternative to spring seeding. Good management and attention to some of the potential pitfalls is required to minimize the risk of establishment failure. For more information refer to "Summer Seeding Forages" on the OMAFRA Forage Website.

Related Links

• OMAFRA Forage Website

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