Clovers are legumes and legumes can capture nitrogen from the air and due to some nitrogen fixating bacteria in their roots, they can use the nitrogen for their benefit, as well as share some nitrogen with surrounding plants.
One method of renovating pastures or improving a hay field by adding clovers is called frost seeding. This is a method of broadcasting clovers in a field in the February time period. It works best to broadcast the seed while the ground is frozen. The freezing action makes the soil surface like a honeycomb, providing small pockets for seed to make good soil contact. This is necessary if seeds are to grow and compete with established plants. If trying to renovate into March, drilling is the recommended method.
One important consideration before frost seeding or seeding period is to determine if the area currently has poor growth. Why is this happening? Is it improper pH? Is it poor grazing management or cutting too low? The soil is not going to grow more of the desired forage if you just broadcast more seed. Things have to be fixed before seeding.
Weeds should be controlled before frost seeding. Once legume plants start to grow, any herbicide application to kill broadleaf weeds will also kill the frost-seeded legumes. Weeds are nitrogen scavengers and not only reduce grass growth around them, but can decrease the quality of forage in a pasture. Read the label on the herbicide to determine time to wait to seed after herbicide application.
It is recommended to remove excess growth before frost seeding. One can use livestock or a brush hog to do this. Removing or cutting this plant material will provide needed openings above the soil to allow seeds to fall to the ground. You can frost seed cool season grass seed or legumes, but frost seeding works best with legume seeds because it is easier for smaller seeds to drop to the soil surface than it is for the larger but lighter grass seeds.
Encouraging legume plants in forage growth can lower production costs. Stands that contain about 30-35 percent legumes generally need no additional nitrogen to obtain good growth. Several research studies have shown that having legumes mixed within a pasture that has a lot of fescue in it, not only increases forage production, but also benefits livestock production factors like improved weight gain and increased conception rates.
Legumes seed must be inoculated before seeding. Some companies apply an inoculant coating on their legume seed and some do not. Therefore, producers need to check when purchasing seed to be sure what they are getting and if they need to apply the inoculant before seeding. Inoculated seed is time sensitive and should be planted promptly after purchase or inoculation.
Finally, as growth begins in the spring, new legume seedlings will have a better chance to start if they have help competing against established plants. Frost-seeded pastures should be grazed lightly or clipped in the spring at regular intervals when grass plants are about 8 inches in height.
This will allow sunlight to enter the canopy so new legume seedlings are not shaded out. However, do not allow animals to graze seeded areas so heavily to heights less than 3-4 inches, as will ruin the new seeding before adequate roots are developed.
If a frost seeding was made in a hay field, do not apply high rates of nitrogen fertilizer to first-cutting hay. Established grass plants in mixed grass/legume stands will out-compete the newly seeded legume plants and shade them out.
Plan to make first-cutting hay on any frost-seeded fields early in the season in mid-May if weather and field conditions permit. This will open the canopy to give light to the new seedlings. Grass height in second-cutting hay will not be as much of a problem, and new legume plants will be further developed to compete better with the grasses.
For more information, contact the UT-TSU Extension Office in Wilson County at 615-444-9584. You can also find us on Facebook or visit extension.tennessee.edu/wilson. Ruth Correll, UT Extension-TSU Cooperative Extension agent in Wilson County, may be reached at 615-444-9584 or firstname.lastname@example.org.