Midwinter is the perfect time to consider frost seeding to improve perennial pastures, especially when a cold spell (without ice and snow) hits that leaves the ground hard enough to drive over easily.
Frost seeding has traditionally been an economical way to introduce legumes to an established grass stand or to establish a red-clover or clover mix in a stand of overwintering small grain.
For pasture application, if the conditions are right and it is managed properly, it can be an opportunity to renovate a sparse pasture without tillage.
Perhaps the most important consideration is that your soil is open and the sward has space to support additional seedlings without too much competition. This means that the existing stand should be somewhat sparse or closely grazed.
Frost seeding, like any seeding event, requires adequate seed-to-soil contact, and this is usually achieved through the “honeycombing” effect of common wintertime freeze-thaw cycles (the best time is when soil is frozen in the morning and thaws during the day). The ground’s expansion and contraction with frost heaving efficiently works the seed into the soil, especially small round seeds such as clover. Grasses have much less success in establishing, since the larger seed is less effective at making its way into the soil. Some smaller-seeded and hulless grasses can work, however. Those with the highest probability of success include ryegrasses, ryegrass-type festuloliums, and hulled orchardgrass.
In a pasture or hayfield situation, a chain drag or light disking can help open up the soil if needed.
You can spin the seed on with a broadcast seeder. This is often done with a three-point hitch-mounted seeder. A good amount of the pasture’s soil should be exposed by a late fall close grazing or mowing, which provides ample opportunity for seed-to-soil contact of the broadcast seed. A bunch-type grass like orchardgrass typically leaves more exposed soil than a sod-forming grass, making it more receptive to frost seeding.
For frost seeding into an overwintering small grain such as barley, wheat, triticale or rye, we often have bare ground between the drilled rows of the small grain during the winter, when the freezing and thawing occur and the clover can get worked into the soil. The clover germinates in spring and begins to grow under the canopy of the small grain. The canopy is opened after the small grain is harvested in summer, and the small legume seedlings are released from the competition with the small grain. The first cutting of the clover hay is often termed “stubble hay” because it will have some small grain stubble in it. The clover hay will over-winter and give a spring hay cutting or a nitrogen-rich green manure before corn the following year.
Red clover is often considered an optimal choice for frost-seeding, since it has superior seedling vigor and is tolerant of varying conditions. Other small-seeded legumes such as white clover, yellow blossom sweet clover, white sweet clover and alsike clover also will work. King’s Three-Way Clover Mix (Medium Red Clover, Ladino White Clover and yellow blossom sweet clover) will work well as a frost-seeded cover crop, and Premium Clover Blend is a good forage mixture.