Frost Seeding Legumes Improves Pastures Several Ways

By Linda Geist

Adding diversity to a pasture can make it more productive than growing tall fescue alone. Diversity can also aid in reducing or diluting the effects of fescue toxicity, improve nutritive value of forage, increase weight gain and enhance soil health, says University of Missouri Extension state forage specialist Carson Roberts.

One way to add diversity is through inter-seeding legumes. Research over the years at the MU Cornett Research Farm near Linneus shows that fescue pastures are more productive when legumes are in the mixture. Maintaining legumes like red clover in a pasture not only improves the quality and forage yield of pastures in the springtime, it also increases quality and forage yield in stockpiled pastures, says Roberts.

Traditionally, legumes are sown at the beginning of the active growing season in April. However, frost seeding can be very successful, he says. Frost seeding, a method of broadcasting seeds over snow- or frost-covered pastures, improves poor pastures at a low cost. Seeds work their way into the soil and germinate as the ground freezes and thaws between winter and spring. Frost seeding is effective because freeze-thaw cycles cause soil surface movement that increases seed-to-soil contact, says Roberts.

The best time to broadcast legumes is when the soil is frozen and snow-covered. This window can be as early as late January in southern Missouri through late February in the northern part of the state.

Roberts says there are a few common situations that can result in stand failure:

• Low pH.
• Poor grazing management.
• Herbicide residual.
• Broadcasting into fluffy, windblown snow.
• Broadcasting on muddy, unfrozen soil.
• Incorrect legume species.

Planning and management reduce chances of failure, says Roberts.

Legumes are less tolerant of soil acidity than most grass species. Establishment is most successful at a pH of 6.0 or higher, but some legumes like annual lespedeza can tolerate a pH as low as 5.0.

Overstocking and/or continuous grazing a frost-seeded pasture in the spring can result in stand failure due to animals grazing the seedlings too closely. However, failure to graze during April and May could also reduce legume germination and growth due to competition from the tall fescue.

Broadcasting on frozen soil with a stable layer of snow is best, says Roberts. Frozen soil will support equipment and mitigate compaction.

Annual lespedeza, red clover and white clover can be used in frost seeding, and other species like alfalfa, bird’s-foot trefoil, hairy vetch and sunn hemp are better sown at other times of the year.

For more information, see MU Extension publication “Seeding Rates, Dates and Depths for Common Missouri Forages” at https://extension.missouri.edu/publications/g4652.