Frost Seeding Your Pastures

Frost seeding, sometimes referred to as overseeding establishes legumes in existing grass pastures. Legumes are broadcast on grass pastures in late winter or very early spring when the ground is still frozen. Freezing and thawing, plus early spring rains, works the seed into the soil. All commonly grown legumes can be established by overseeding. Because of their greater seedling vigor, red clover, alsike clover, and ladino clover are more easily established than other legumes like alfalfa. Frost seedings are most successful in bare and disturbed pasture areas where cattle have grazed closely.

This allows sunlight down to the ground when the newly germinated plant begins its growth among the established grass. It seems that bunch-type grasses such as our fescues and orchard grasses offer less competition to legume seedlings than vigorous stands of sod-forming bromegrass, bluegrass, and bermudagrass. Frost seeded legumes and grasses often have poor establishment in years with abnormally dry springs and early summer hot weather. Red and alsike clover stands last about two years. Ladino and other white clover stands may last three or more years.

Red and Ladino clovers should be frost seeded in mid February for best results. Annual or Korean lespedeza can be considered for frost seeding in Southwest Missouri in early March. Lespedeza is tolerant of poor fertility and irregular drainage sites. Lespedeza seedlings are slow to establish, but contribute to production by mid- to late-summer.

Seeding rates for overseeding should be equal or preferably higher than when seeded on prepared seedbeds. Extra seed helps compensate for the reduced chance of good seed coverage and the expense is offset by lower costs for labor, tillage operations, and seeding equipment. The following seeding rates in pounds per acre are suggested. when seeded alone: Red Clover 8 to10 lb per acre, Alsike Clover 3 to 5 lb per acre, Ladino Clover 3 to 5 lb per acre , and Lespedeza 8 to 10 lb per acre.

The following steps are suggested for successful overseeding:

1. Select a suitable site. Chances of success are greater on thin grass stands than on thick, vigorous stands because there is less competition for legume seedlings.

2. Control weeds. If possible, plan a year ahead and spray weeds with 2,4-D. Weeds reduce stand establishment and can be controlled only by clipping once legumes are established.

3. Soil test and apply needed lime and fertilizer. Adequate plant nutrients aid establishment and increase yields. If possible, apply needed lime one year ahead of seeding. Nitrogen should not be used the season before or the year of frost seeding because it stimulates grasses and weeds, making them too competitive. Phosphorus and potassium, however, are needed by legumes.

4. Graze closely the fall before seeding. This reduces grass competition and aids establishment. Although it is not considered necessary, disturbing the soil lightly with a disk in the fall before seeding may help legume establishment.

5. Broadcast seed in February or early March. Seeding should be done when the ground is still frozen.  Probability of success decreases with the onset of spring due to higher surface soil temperatures and lower moisture.

6. Manage grazing after seeding. Control of grass and weed competition during the first two or three months of the growing season is critical for the establishment of adequate legume stands. Use moderate periodic grazing after the grass starts growing, but avoid close grazing. Some mowing may be necessary to help control grass and weeds.

7. Inoculate legume seed with rhizobium bacteria. This insures adequate amounts of nitrogen are being produced by the legumes for all plants to use.
(By John Hobbs, Agriculture and Rural Development Extension Specialist)