Northwest Ohio soils ideal for frost seedings

Soils in our area have a period of thawing and freezing during the transition from winter to spring. This process can disturb and mix the upper soil layer by the swelling and shrinking properties of clay, which is abundant in many of our soils. Farmers take advantage of this activity by a practice that is called frost seeding. Frost seeding is the process of applying seed over an existing pasture or hay field in late winter or early spring so seed can be moved into the soil during the thawing and freezing activity. The objective is to renovate, fill in dead spots, and improve the overall quality of the pasture without killing existing plants and starting over. Farmers may also frost seed into wheat fields to have forage for livestock after wheat harvest. Forage seeds need to have good contact with the soil and be near the soil surface for germination and early growth. Frost seeding requires areas of bare soil to be successful. The seeding will fail if there is too much vegetation and the seed gets caught in the residue. A farmer may prepare for a frost seeding the previous fall by reducing vegetation without killing the pasture by close grazing, low mowing or light tillage. Legumes are the most common species used for frost seedings. Forage legumes have excellent nutritional value for livestock, and have the ability to obtain nitrogen from the atmosphere and release it for plant use. Legume seeds are also heavier than grass and have a better chance of getting through the vegetation to bare soil. Red clover is the most common forage legume used for frost seedings. It has good seedling vigor and tolerates a wide range of soil pH and soil fertility conditions. Red clover grows as a short-lived perennial typically lasting for two years. Newer varieties survive longer, but seed costs will be higher. Birdsfoot trefoil may be mixed with red clover. It is a persistent perennial but slow to establish, and may not become a major part of the pasture until the second year after the frost seeding. This may work well, however, since red clover is declining the second year. Another popular legume is white clover. White clover is a perennial clover that thrives in the cool spring weather. It tends to be a short legume and may not get adequate light for optimum growth when seeded with taller grasses. However, companies have developed newer varieties that tend be more upright. Frost seeding rates vary among forage species. The smaller the seed, the smaller the seeding rate. For example, the seeding rate for white clover is 2 to 3 pounds per acre, and the rate for red clover is 6 to 8 pounds. A bacterial inoculum should be included in the frost seeding if the forage legume has not been grown in a pasture for several years. Inoculum ensures the presence of Rhizobia bacteria, which gives the plant roots the ability to fix atmospheric nitrogen. The inoculum is generally added as a seed treatment by the seed supplier. Common (generic) red clover used to be grown in the area and was readily available at a lower cost than branded seed. Seed production of red clover has been declining in our area for the past decade because of competition for land from higher value crops such as corn and soybean. Higher seed costs and the risk of establishment failure has also caused the practice of frost seeding to become less common in our area. The cost of red clover seed has increased because of lower supplies of common red clover seed and the larger demand for legumes as a cover crop. There are still farmers who will take advantage of the spring thaw and freeze cycle and use frost seeding to improve pastures and provide livestock with high-quality forage. Besides renovating pastures, some farmers frost seed red clover into existing wheat fields. Just like in pastures, the clover seed works into the ground by the thawing and freezing action of soils. The clover does not cause competition problems with the wheat and has time for growth after the wheat is harvested. The farmer will then have a red clover field to harvest for hay in late summer or early fall. The next two to three weeks is generally the time that farmers will try to frost seed. However, the success of the seeding will depend on the amount of bare soil exposed and the window of thaw-freeze activity of the soil. Lentz is Extension educator for agriculture and natural resources for Ohio State University Extension-Hancock County.