Farmers can transform pastures from weedy patches to forage producers, but it demands applying fall herbicides, and then a winter overseeding plan.
This year, some pastures were overrun with biennial or perennial weeds such as spotted knapweed, wild parsnip, thistles, Canada thistle and horse nettle. Terry Halleran, University of Missouri Extension agronomy field specialist, says fall is a good time to tackle these stubborn weeds.
During this season, these weeds move sugar to their roots, preparing for spring regrowth. Applying systemic herbicides like 2,4-D, dicamba, glyphosate and aminopyralid ensures the herbicide is effectively transported to the plant’s roots and rhizomes, he explains.
“Systemic herbicides enter the plant through its foliage and kill the plant by disrupting normal plant function,” Halleran adds.
After clearing the weeds, he suggests farmers consider overseeding with clovers and annual lespedezas. This will increase forage production and improve plant diversity in pastures next spring.
Tackle weeds first
For biennial plants such as wild parsnip and thistles, Halleran says to focus on their first-year growth stage in the fall, when they are low-growing rosettes.
“There is no point in wasting time and herbicide on the second-year growth stages of the biennial weeds in the fall,” he adds, “as they have already gone to seed and are dead or dying.”
For annual winter weeds, which begin their life cycle in late summer, applying herbicide at the start of germination in fall and winter can prevent their growth in spring.
Next, farmers should develop a plan to overseed pastures during the winter months with a diverse seed selection.
Create a frost-seeding plan
Halleran offers the following suggestions for successful overseeding:
While frost seeding is an effective method to establish legumes in existing grass pastures, some farmers may need a refresher.
Here’s a step-by-step guide to successfully frost-seed your pastures:
1. Timing
Mid-February. Target for seeding red and ladino clover.
Early March. Ideal for seeding annual or Korean lespedeza, particularly in southwest Missouri.
2. Preparation
Graze closely the fall before seeding. This reduces grass competition and aids establishment. Disturbing the soil lightly with a disk in the fall before seeding may help legume establishment.
Soil test. Adequate plant nutrients aid establishment and increase yields. If possible, apply needed lime one year ahead of seeding. Do not use nitrogen the season before or the year of frost seeding as it stimulates grass and weed growth. Phosphorus and potassium are needed by legumes.
3. Selecting legumes
Choose legumes based on your pasture conditions. Red clover, 8-10 lbs./ac.; alsike clover, 3-5 lbs./ac.; ladino clover, 3-5 lbs./ac.; lespedeza, 8-10 lbs./ ac.
MIx species. Consider mixing species for better diversity and resilience.
4. Seed preparation
Quality seed. Use high-quality, certified seeds to ensure good germination rates.
Calculate seed quantity. Increase seeding rates slightly to compensate for potential coverage issues (e.g., double the rate if necessary).
Inoculate legume seed with rhizobium bacteria. This ensures that adequate amounts of nitrogen are being produced by the legumes for all plants to use.
5. Seeding method
Broadcasting. Use a hand-held or mechanical broadcaster to evenly distribute the seeds over the pasture.
Timing of application. Aim to seed when the ground is still frozen. Probability of success decreases with the onset of spring because of higher surface soil temperatures and lower moisture.
6. Environmental conditions
Monitor weather. Look for periods of thawing and subsequent freezing; this natural process will help incorporate the seeds into the soil.
Early spring rain. Favorable moisture conditions will enhance seed germination, so timing with expected rainfall is beneficial.
7. Post-seeding care
Minimize disturbance. Avoid heavy grazing immediately after seeding to allow seedlings to establish.
Monitor growth. Keep an eye on the growth of newly established legumes, ensuring they are not overly shaded by existing grasses.
8. Evaluate results
Check establishment. After a few weeks, evaluate the establishment of the legumes. Look for germination and growth patterns.
Adjust future practices. Based on results, adjust your seeding rates or species for future frost seeding.
9. Long-term management
Grazing management. Implement rotational grazing to prevent overgrazing and promote a healthy balance of grasses and legumes.
Annual monitoring. Continue to monitor and manage your pasture for fertility and plant diversity over the years.
By following these steps, Halleran says farmers will set themselves up to successfully frost-seed pastures to reduce weed pressure and enhance biodiversity.
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