The time of the year when frost seedings are most effectively done will be here before long. One can use this method to renovate pastures, improve stands, or alter the species mix within a pasture. Producers should remember however, this is only a means to get the seed in good contact with the soil. If the area you intend to frost seed currently has poor grass/legume growth, the first thing you need to determine is “why the problem has occurred?” Adding more seed to soil that lacks proper nutrient levels, has a pH that is to low or high for the intended crop, or if the crop is not managed properly for the plant species desired (for example – repeated close grazings), the soil is not going to grow more of the desired forage if you just broadcast more seed.
When plants are severely grazed, or re-grazed before a sufficient rest period has elapsed, the plant takes energy that has been stored in the roots as carbohydrates to support new leaf growth. As carbohydrates are removed from the roots, the root dies, separates from the plant and eventually decomposes. This process continues until enough green leaf surface once again develops to catch sufficient amounts of solar energy that support additional leaf growth and reestablish lost roots. Depending on the severity of root loss, slow re-growth may be noticed for a considerable amount of time.
Areas chosen for frost seeding should not have large amounts of undecomposed plant material remaining in the field. If it does, put animals in those areas now to graze the area closely before seeding. Removing this plant material will make openings above the soil allowing seeds to fall to the ground. Frost seeding works best with legume seeds typically, because it is easier for smaller seeds to drop to the soil surface than it is for the larger, but lighter grass seeds. Making a muddy mess of an area is not the goal, but if weather conditions are going to cause livestock to trample an area, because you do not have a heavy use feed pad to put them onto, the sacrifice area may as well be where you plan to frost seed.
Encouraging legume growth in pasture fields can minimize production costs by reducing the amount of nitrogen fertilization necessary for maximum forage growth. Stands that contain approximately 30% legumes generally need no additional nitrogen added. Legumes also improve the quality characteristics of a grass stand. Frost seeding offers several potential advantages when properly implemented. These may include: establishment of forage in undisturbed sod, reduced labor, energy and cash expense compared to conventional tillage methods, the ability to establish forages with minimal equipment investment, and little, if any, “non-grazing” period.
Late winter, February or early March, is a good time to frost seed pastures in our area. Broadcast your selected seed while the ground is frozen. The freeze and thaw cycle of the soil is needed for seeds to obtain good soil-to-seed contact. This is necessary if seeds are to grow and compete with established grasses, other legumes, and or weeds.
Planting mixtures and seeding rates differ greatly. Desired species and number of seedlings wanted in the final stand determine how much to plant. As a rule of thumb, if legumes are already present in the pasture, 3-4 lbs. of red clover and 1-2 lb. of ladino or alsike clover seed per acre works well. Birdsfoot trefoil could also be used at 2-3 lbs. per acre. If no legumes are currently present in the stand or seeding one species alone, doubling the above rates may return better results. Also, remember to inoculate legume seed when planting.
If grasses are to be frost seeded into existing pastures, perennial or annual ryegrass, orchardgrass, or smooth bromegrass would be recommended. Perennial/annual ryegrass should be seeded at 2-3 lbs. along with orchardgrass 2-3 lbs. or smooth bromegrass 8-10 lbs. per acre. When planting, using a spinner type seeder, do not mix legume and grass seed together. Grass seed will not spread as far as legume seed causing an uneven stand. Make two trips over the pasture and adjust spacing as needed for the type seed being sown.
In the spring, excessive growth and competition should be controlled. Frost seeded pastures should be grazed or clipped in the spring at regular intervals to allow sunlight to enter the canopy. Do not allow animals to graze plants low enough the first or second rotations that they ruin the new seedlings before adequate roots are developed.
Summary- Frost seeding will not increase the productivity or quality of a pasture if soil nutrients and pH are not in acceptable ranges for the species you are trying to produce. Most often, pastures are a product of management practices. Many times a change in grazing practices (allowing rest periods) or addition of soil nutrients will correct declining pasture production. If you are thinking of making a frost seeding and do not know what your nutrient levels are, a soil test can be a valuable tool. It can tell you if your pastures need more seed or just more “feed”.