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Time to kill pasture weeds, boost forage production

Here are some fall weed-control tips, plus frost-seeding techniques for maximum spring growth.

Mindy Ward, Editor, Missouri Ruralist

October 18, 2024

3 Min Read
 fall herbicides being applied to pasture
SPRAY ON: Applying herbicides in the fall will remove weeds such as thistle from pastures. Then plan to reduce weed pressure in the spring by overseeding clover and legumes. Wanda Jewell/getty images

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.

Read more about:

Pasture Management

About the Author

Mindy Ward

Editor, Missouri Ruralist

Mindy resides on a small farm just outside of Holstein, Mo, about 80 miles southwest of St. Louis.

After graduating from the University of Missouri-Columbia with a bachelor’s degree in agricultural journalism, she worked briefly at a public relations firm in Kansas City. Her husband’s career led the couple north to Minnesota.

There, she reported on large-scale production of corn, soybeans, sugar beets, and dairy, as well as, biofuels for The Land. After 10 years, the couple returned to Missouri and she began covering agriculture in the Show-Me State.

“In all my 15 years of writing about agriculture, I have found some of the most progressive thinkers are farmers,” she says. “They are constantly searching for ways to do more with less, improve their land and leave their legacy to the next generation.”

Mindy and her husband, Stacy, together with their daughters, Elisa and Cassidy, operate Showtime Farms in southern Warren County. The family spends a great deal of time caring for and showing Dorset, Oxford and crossbred sheep.

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