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Time to consider frost seeding

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Column by Doug Shepherd, Hardin County Extension Service agent

It’s the time of year forage producers really get to thinking about reseeding pastures and hay fields.

Last summer’s drought took a toll on stands of legumes and grasses in some fields, so producers are wondering what’s really going to be there this spring. Frost seeding is a good option to get clovers back into pastures and hay fields, and based on the calls we’re getting here recently, many producers are considering using this option, but have questions — especially on the recommended timing.

Frost seeding allows seeds to be inter-seeded into undisturbed soils by scattering seed on top of the ground. The freezing and thawing action of the soil works the seeds into the soil where they can germinate. In Kentucky, the ideal time to frost seed is between Feb. 10 and March 1, with mid-February preferred.

It is important to consider what forage species can be frost seeded successfully. Seeding red and white clover is recommended using this method. While it is possible to frost seed some grasses, it typically is less successful and generally not recommended.

It is not recommended to frost seed alfalfa because of highly inconsistent results. The technique can reduce machine use and seeding cost. It also is beneficial as it can be done at times when using heavy machinery would damage pastures such as during extremely wet periods.

Individual pasture characteristics also should be considered. Seeding nitrogen-fixing legumes into existing grass stands will reduce nitrogen fertilizer costs greatly, and can increase pasture yields and quality. Frost-seeding legumes can be very successful when performed correctly using the best-suited species, which generally are red and white clovers.

Birdsfoot trefoil is another option and often is frost seeded in a mix with red clover. This non-bloating legume can be slow to establish and often is sparse until the second year. After it is established, this long-lived perennial legume has been shown to produce a healthy stand for 10 or more years.

Annual lespedeza is another legume sometimes seeded using this low input method. This warm-season, non-bloating legume is fairly drought tolerant and will be very productive when cool-season forages are suffering from “summer slump.”

Few grass species have been proven to be effective when frost seeded. In trials, perennial ryegrass and annual (Italian) ryegrass are the only grasses which established well enough to be a reasonable option using this method. Orchardgrass has been somewhat successful under favorable conditions but frost seeding orchardgass is not a suggested practice. It is recommended to drill most grass species for maximum success.

It is necessary to follow basic seeding and management guidelines for successful frost seeding. Having good seed-to-soil contact is vital. Reduce the vegetative cover on the area to be seeded to allow more seed to reach the soil surface. Broadcasted seed needs to fall directly onto the soil surface to be worked into the soil through freeze-thaw action. This can be accomplished by heavy grazing in the late fall and early winter or by mowing the area to a low height prior to seeding. It may be more difficult to expose sufficient soil in existing stands of sod-forming grasses.

Reducing competition from existing forages and weeds also is crucial. Similar to creating seed-to-soil contact, grazing or mowing closely reduces competition. In the spring, weed pressure may increase and weeds may need to be controlled by management methods or by herbicide application to allow seedlings to establish. It is important to remember existing clovers will be killed by herbicide applications. Be sure to read herbicide labels and follow recommended waiting periods before seeding clovers or grazing animals.

Although bloat may be an issue when grazing some legumes, a stand mixed with non-bloating legumes and grasses reduces the likeliness of bloat. Basic management to reduce bloat should be followed as described in the UK Extension publication ID-186, “Managing Legume-based Bloat in Cattle” which is available at the Hardin County Extension Service office and online.

Also, we have received new forage variety trial publications in the office, so before you purchase seed this spring, check out which varieties performed the best over the years in the UK Forage Variety Trials. There are trial results for all the major forage species used locally: alfalfa, red and white clovers, orchardgrass, tall fescue, etc. These publications also are available at the Hardin County Extension Service office and online.

Contact our office for further information or for answers to any other questions you might have on reseeding pastures or hay fields this spring.

Doug Shepherd is a Hardin County Extension Service agent for agriculture and natural resources.