As we move through late winter and early springtime, one of the first tasks on the list for farms with pastures should be to evaluate their condition. If stands are thin, consider frost seeding as an option to thicken your pasture.
Before we begin to talk about seeding, it is important to note that frost seeding (or overseeding of pastures in general) is not a substitute for poor fertility of pastures. Proper pH and fertility are essential for desirable production of pastures. Soil tests should be taken regularly (at least every 3 years), and corrective measures taken.
Although using some type of tillage to renovate pasture has a higher rate of success, using frost seeding is a less expensive option that can effective is done at the right time and managed properly. Make sure that you can achieve maximum seed-to-soil contact. Often times, a pasture that has been very aggressively grazed into the fall will present a good opportunity for frost seeding. Using a chain drag or running over the field lightly with a disk can open up the stand as well.
Frost seeding works as the ground "honey combs" during this time of year. As temperatures moderate to above freezing during the day, but drop below freezing at night, the seeds have an opportunity to work down into the soil surface. The trampling effect of livestock densities can also be effective to obtain seed to soil contact. Early morning frost seeding, before the soil surface begins to thaw, is recommended. If the soil surface is "slimy", wait to seed until you get another morning when the soil has frozen again.
Most often, we recommend using frost seeding to introduce forage legumes into an established stand. Legumes have a much better success rate than grasses. Red clover is usually the species most recommended for frost seeding, because of factors including seedling vigor and wide tolerance to pH, fertility, drainage, and drought. Obtaining a desirable stand of grass species from frost seeding is much more difficult. Research at the University of Wisconsin (West and Undersander, 1997) showed that perennial ryegrass and orchardgrass exhibited the best establishment success.
If you plan to attempt frost seeding of a grass, be aware that you will need to make a separate pass with your seeder, as grasses will not spread as far as legumes.
Frost seeding can be done with any type of a broadcast seeder. This can be done by hand, tractor 3-point hitch, or ATV.
For more information, see an article written by Heather Darby of the University of Vermont.