Frost Seeding Grasses and Legumes

by Glen Arnold, Putnam County

Early March is frost seeding season. In Putnam County farmers use this time to apply red clover to wheat fields and allow the freezing and thawing weather cycle to work the seed into the soil.

Some fields will have red cover applied from an airplane while some farmers will use four wheelers or fertilizer buggies to apply clover seed with fertilizer. When applying this mixture with a “spinning seeder,” farmers should remember the fertilizer can travel twice as far as the seed.

This is also the time of year when farmers think about re-seeding their pasture and hay fields. As before, farmers apply seed to the ground and the freezing and thawing of the soil to provide seed-to-soil contact, allowing germination of the seed. There is a little more risk of the seed not germinating than with a “traditional” seeding, but the cost and time is a lot less. The key is to have exposed soil.

In general, legumes or clovers work better for frost seeding, as compared to grasses. This might be because legume seeds are typically heavier than grass seed and that may help them get into the soil better than grass seed. Also, it could be partly a matter of competition.

A grass seedling is competing directly with existing grass plants for moisture, sunlight, and nutrients. A legume seedling, because it has somewhat different requirements and is able to utilize resources not needed by the existing grass, has an easier time getting established. The advantage to frost seeding a legume such as red or white clover into a pasture is that legumes “fix” nitrogen, typically in excess of their own needs.

The existing grass plants use the excess nitrogen, which improves their quality as a feedstuff. Pasture and hay fields that have thin stands and exposed soil are good candidates for frost seeding. Once legumes become established in a stand of pasture grass, and compose 25-30 percent of the stand, there is no need to apply supplemental nitrogen, so this portion of fertilizer costs is reduced.

Frost seeding is a nearly universal practice among graziers, recommended by most forage experts and consultants, but there’s remarkably little hard data out there documenting its effectiveness. Lots of recommendations, but very little research has been done on how to make sure you’re successful. Looking through the scientific literature there are few published studies evaluating frost seeding methods and species.

Generally, the best source of information in Ohio on this practice remains farmers and their on-farm experience. Frost seeding is a method whose success is dictated largely by weather conditions. Some years it just doesn’t work, while in others, an excellent stand is achieved. There is universal agreement the two most important factors are achieving good seed-soil contact and reducing competition from established plants.

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