With the grazing season just around the corner, now is the time to be making pasture improvements for the upcoming grazing season. Some pastures could benefit from improvements, especially following the 2017 drought.
One way to improve pastures is by adding legumes and/or grasses into existing pastures stands, according to Joe Sellers, Iowa State University (ISU) Extension beef specialist, and Rebecca Vittetoe, ISU Extension field agronomist.
Why add a legume to a pasture? Adding or increasing the presence of legumes in existing pastures not only helps improve forage quality but also reduces or eliminates the need for nitrogen fertilizer.
Another advantage to incorporating legumes in a pasture is that mixed grass and legume pastures provide more uniform production during the warm summer months when many of the cool-season pasture grasses go dormant. Before introducing legumes into pastures, it is important to have thistles and other broadleaf weeds under control.
Adding grasses into existing pasture stands improves pasture productivity by thickening up the stand. It is also common to use a grass-legume mixture to improve pastures. When using a grass legume-mixture be sure to select compatible grass-legume mixes. For instance, birdsfoot trefoil is easier to establish in orchardgrass or Kentucky bluegrass than in smooth bromegrass, tall fescue, or reed canarygrass. Alfalfa and red clover would be better fits to use with smooth bromegrass, tall fescue, or reed canarygrass.
Two ways to add forage species into existing stands are frost seeding and interseeding.
Frost seeding
Frost seeding is the spreading of forage seed onto existing pastures during the late winter or early spring while the ground is still frozen. Typically, this occurs at the end of February and in early March. The idea behind frost seeding is that the freeze-thaw cycles and early spring rains will help provide shallow coverage of the seed.
A common misconception with frost seeding is that the seed should be spread on top of snow. Actually, the goal of frost seeding is to get the seed on bare soil. If seeded on top of snow and the snow melts quickly, it could cause the seed to wash. Therefore, ideally frost seeding would be done without snow cover. It is okay if snow falls on top of the frost seeding.
In springs without the traditional freeze-thaw cycles, overseeding can still work when there is adequate soil moisture as cattle hooves can help work the seeds in. Use flash grazing to manage existing grass competition.
Frost seeding is the simplest and is likely the least expensive method of adding new forage legumes or grasses to existing pastures. However, while it may be the simplest and least expensive, it can also be the least consistent. Usually the success rate of frost seeding is 60 percent; however, to increase the success rate, select the thinnest pasture sod areas or where bare soil has been exposed due to heavy or over-grazing or disturbance. Pastures that were grazed very short last fall would be good candidates for frost seeding this year.
As far as what species work best with frost seeding, red clover has been the Iowa forage species of choice for frost seeding. White clover and birdsfoot trefoil are examples of other legume species that can be frost seeded but with less success than red clover. Generally, frost seeding does not work as well with grasses.
Interseeding
Interseeding, which involves drilling a legume, grass, or grass-legume mixture into an existing pasture, is typically done from mid-March through late April. Interseeding typically provides more consistent results compared to frost seeding. However, with interseeding, it is important to watch seeding depth. Ideally seeding depth is one-fourth to one-half inch. Planting deeper than that can result in poor stand establishment.
To improve the success of interseeding, closely graze the pasture in the fall or spring before interseeding to reduce sod competition. Another option that can be used to help temporarily reduce sod competition is the use of contact herbicides. Use only labeled herbicides for sod suppression, and be sure to read and follow label direction.
Soil fertility
To help improve the success of both frost seeding and interseeding, adequate soil fertility is important. From a pH perspective, a soil pH of at least 6.5 is recommended for grass, clovers, and birdsfoot trefoil, and for alfalfa a soil pH of 6.9 is recommended. Ideally lime would be applied a year before seeding. Adequate phosphorus and potassium are also important to improve establishment and production. Do not apply early season nitrogen to frost seeded or interseeded areas to minimize early season growth and competition from already established plants in the area.
