The temptation to graze some paddocks a bit tighter than normal might have gotten the best of us this fall as we were well aware of high feed costs moving forward. For those acres grazed a bit short, there are options to boost productivity or aid in long term recovery, one of which you can implement very soon: frost seeding.
The ideal window for frost seeding legumes in Iowa is from the end of February through early March. Frost seeding, is simply broadcasting seed on existing pasture when the ground is still frozen. The freeze-thaw cycle moves the seeds into the soil to establish seed to soil contact and encourage germination.
Is your pasture a good candidate to frost seed? Consider these factors when assessing the likelihood for success.
- Competition – bare ground or a thin grass stand greatly increase the likelihood of germination and establishment. Non-sod forming stands tend to do better, though sod grass stands can still respond well when grazed or clipped short. Weed pressure is also an important consideration because after establishment, controlling weeds without killing off the frost seeded legume is challenging.
- Soil nutrients and fertility – If you know the thin grass stand in an area is due to poor soil rather than grazing management, frost seeding without addressing nutrient deficiencies in the soil will likely lead to short-lived results. Instead, consider addressing soil shortcomings this fall and interseeding or frostseeding for the next growing season.
- Species and rate – Legumes, specifically red clover and birdsfoot trefoil have shown the most success in various frost seeding trials in Iowa. Grasses can be frost seeded, but with less success than legumes and are not recommended. Seeding rates can vary based on how much bare ground is present, but in general, a rate more comparable to that used in a prepared seedbed will be more successful. The cost of additional seed is offset by reduced labor and tillage costs that are required to interseed via other methods.
- Grazing management post-seeding – In the first months of the growing season, a balance of grazing or mowing to reduce competition, while avoiding grazing new forage too closely should be achieved to establish a long-lived, productive stand. Therefore, sacrifice paddocks or calving pastures that will be continuously grazed until pasture turnout are poor candidates. Additionally, pastures that will not be grazed until the end of the spring flush might result in the already established grasses choking out newly seeded legumes.