Considerations And Techniques For Reseeding Pastures

Pasture improvement can be achieved with numerous approaches. Minor improvements can be achieved by implementing better grazing management strategies, such as rotational grazing or resting pastures, or by controlling unwanted weeds that compete with desirable forage plants. However, sometimes minor improvements simply cannot achieve the desired outcomes for your pasture. If that is the case, you may want to consider a more major improvement strategy for your pasture — reseeding.

Why reseed?

Reseeding can be used to improve forage production or forage quality in a pasture, reduce erosion potential, increase performance of livestock, restore a healthy plant community, improve wildlife habitat, or introduce competitive plants that resist weed invasion. In general, reseeding should be considered when less than thirty percent of the ground is covered with desirable vegetation. Complete stand establishment, which involves destroying all existing vegetation in a pasture and establishing new vegetation, or supplemental seeding, which involves maintaining existing vegetation and seeding over it, can be considered. Which approach is most suitable depends on your goals and objectives for the pasture.

Deciding what to plant

Identifying the long-term objectives of a seeding project will help you make sound, short-term decisions that will bolster the success of your seeding project. Are you using the forage for grazing or haying? If your objectives include grazing, when do you plan to graze the pasture? How much forage is needed? Are you trying to minimize erosion or resist weed invasion?

It is very important to choose species and cultivars (cultivated varieties of plants selected for desirable characteristics) to match both your goals and the characteristics of your site. Forage species differ in moisture and soils requirements (i.e., soil texture and salinity) and they also differ in their season of growth, ease of establishment, and persistence in a plant community. Examples of grass species that have been used successfully in reseeding projects in Montana, as well as some of their character traits, are displayed in Table 1.

Native or introduced species have both been successfully used to reseed pastures in Montana. Generally, personal preference dictates whether native or introduced species are chosen. However, for sites susceptible to weed invasion, it is important to keep in mind that many introduced species are more competitive against weeds than native species and perennials are more competitive than annual species. For example, crested wheatgrass, an introduced bunchgrass, and thickspike wheatgrass, a native, rhizomatous grass, are two species that compete well against weeds.

Species performance is greatly influenced by available moisture on the site, therefore, considering the local climatic conditions, annual precipitation, and potential for irrigation on the site is critical when choosing species to seed. In general, seeding projects are more risky and forage production is lower on sites with lower annual precipitation levels.

Intended season of use for the pasture, if grazing is one of your goals, is important when choosing what species to plant. Cool-season plants, which are predominant across Montana, initiate growth in the spring and produce forage earlier in the grazing season than warmseason plants, which initiate growth in late spring to early summer and are best suited to mid- to late-summer grazing. Cool-season plants, however, can provide forage in any season when managed correctly, and are most commonly used in reseeding projects in Montana.

Planting species mixtures in a pasture is generally more beneficial than planting a single species, even when the longterm goal is to have one, dominant species in the pasture. When planning for a single species planting, design a seed mix that includes one species you want on the site longterm and another species or two that establish quickly and are short-lived, such as annual plants or short-lived perennials. Examples of annual plants that establish quickly and can be used to protect soil and slowerestablishing perennial plants on the site include annual ryegrass and Regreen (a sterile cross between wheat and tall wheatgrass). Slender wheatgrass is one example of a short-lived perennial plant that is quick to establish. When planning for a multi-species planting, use a minimum of two to three and a maximum of five species in the mix. These plants should have similar season of growth, palatability, grazing tolerance, and regrowth potential. Multi-grass mixtures or grass-legume (e.g., alfalfa, trefoil, clover) mixtures can be used, depending on your goals. Legumes, which naturally fix nitrogen (collect nitrogen from the atmosphere and convert it to useable forms), are beneficial in a seeding because of their ability to produce their own nitrogen, which is released to other plants once the plant or part of the plant dies. Again, it is a good practice to choose one species to include in the seed mix that establishes quickly to protect soil and slower-establishing perennials, as well as to out-compete weeds initially, and to choose other, compatible species to maintain the longevity of vegetation on the site.

Certified seed should be used when reseeding pastures, when possible. Certification of seed ensures uniformity and that the seed has the genetic potential to perform in the field, as well as reducing the potential for contamination by weed seeds. Seed that is not certified is considered “common” seed. If you choose to use common seed, make certain it is obtained from a site with similar environmental and physical characteristics as your pasture to ensure optimal performance.

Be certain to use appropriate seeding rates for the species selected. Seeding rates for species and cultivars are often expressed in pounds of pure live seed (PLS) per acre. In order to determine the amount of actual bulk seed to apply, you will need to know the percent purity and percent germination of the seed. The amount of bulk seed needed per species is calculated by dividing the pounds of PLS by the product of the percent germination and the percent purity of the seed (see Figure 1 for calculation method).

When to seed

Seeding cool-season grasses can be done in either early spring to capitalize on late-winter snows and early-spring rains, or can occur in late fall (dormant seeding). Dormant seeding should occur after the soil temperature is below 55 degrees F for one to two weeks, which corresponds with the time just prior to the soil freezing when soil moisture and temperature are low enough that the risk of seed germination is minimal. Dormant seeding, however, is less compatible with planting legumes. Therefore, seed mixes that include legumes should be planted in the spring. Planting cool-season species in late summer (prior to mid-August) can be successful when irrigation water is available.

How to seed

Pasture forages are most successfully established when seeding occurs on a cultivated seedbed. However, not all situations are conducive to cultivation, such as partial renovation projects where existing vegetation is maintained or when pastures are rocky or have steep terrain. Despite the seeding method, the seedbed should be firm enough to support seeds and allow for maximum seed-to-soil contact, but loose enough to allow newlygerminated seedlings to establish roots and penetrate the soil. A seedbed is ready for seeding if your heel penetrates the soil about ¼ inch when walking across the soil. Seedbeds can be prepared by chiseling, plowing, harrowing, or dragging heavy objects over a site. For partial renovation projects, harrowing or dragging are recommended over more drastic disturbance methods to minimize damage to established plants.

Drilling or broadcasting are commonly used planting methods for pastures in Montana. Other methods include hydroseeding, hay mulch seeding, island planting, plugging, and sprigging. Montana State University EB170, Revegetation Guidelines for Western Montana: Considering Invasive Weeds, provides an overview of different seeding methods and can be accessed at www.msuextension. org/publications/Agand-NaturalResources/EB0170.pdf.

The success of a reseeding project hinges on several things, including a little luck. Knowing what your long-term goals for the site are and matching forage species to your goals and site conditions are the first steps. Understanding the pros and cons of different seeding times and techniques will assist you in deciding what the best approach is for your pasture. And, finally, proper long-term management of the stand, including grazing management and weed control, will ensure maximum productivity and promote the longevity of the stand. For more information on establishing pastures in your area, contact your local county or reservation Extension agent. Another great resource is Montana State University EB19, Dryland Pastures in Montana and Wyoming, which can be found at www. msuextension.org/store/Products/ Dryland-Pastures-in-Montana- and-Wyoming__EB0019. aspx.