With the changing of the seasons, pasture renovation is top of mind for many small farmers. When you’re considering making management changes to your pasture, you should start by thinking through your goals for your pasture:
- What changes would you like to see and why?
- Would you like different forage plants growing in your pasture?
- Do you need to change the productivity level of your pasture?
- Are there more weeds than you’re comfortable with?
- Would you like a denser stand of forage species?
If you’re thinking about making changes to the composition of your pasture, then you’re thinking about renovating your pasture. "Pasture and Hayland Renovation for Western Washington and Oregon" is a comprehensive guide to pasture renovation and provides a detailed discussion on considerations and best practices for working up your soil in preparation for full renovation. This is a great resource to start with if you’re considering renovating your pasture.
It’s a common belief that the only way to change the species composition of a pasture is to kill everything in the pasture and start over. However, an alternative exists in a practice called overseeding. Overseeding is the practice of improving a pasture by seeding into an already growing pasture. Overseeding can be a great alternative to fully renovating pastures if you’re looking to improve forage quality, introduce new forage species into your pasture mix, or fill in a declining pasture. It can be particularly valuable for folks without access to all the farm equipment required for a major renovation project or those folks with long established pastures on sites difficult (rocky, steep, etc.) to farm.
However, it’s important to know that overseeding is not a good fit for every pasture scenario. For instance, if your pasture consists primarily of more weedy species than desirable forage or the soil is compacted, restricting plant growth, it will likely be more resource-effective to fully renovate your pasture. Additionally, while overseeding may sound like a simpler, less expensive process than killing and replanting, thoughtful planning is necessary to get successful plant establishment and growth when overseeding. Careful management is required to help newly seeded plants compete with the existing vegetation. In this article, we will discuss best practices and considerations for overseeding pastures.
Considerations before renovating
Sometimes renovation isn’t the solution to the problems you see in your pasture. Before planning to do any kind of renovation, including overseeding, in your pasture, consider the following.
Do you know what plant species are growing in your pasture today?
In some cases, pastures have plenty of desirable forage plants but those plants aren’t growing well because of issues with grazing management or soil conditions. Consider using a tool like the "NRCS Pasture Condition Score Guide" to assess your pasture. If you need help identifying the desirable and undesirable grasses in your pasture, check out this resource: "A Partial List of Vegetative Characteristics of Common Western Washington and Oregon Pasture and Hayland Grasses."
Have you evaluated your management practices?
If you overseed your pasture, but make no other management changes, you’ll likely find that your pasture is in the same condition it was prior to overseeding within a year or two of overseeding. "Introduction to Pasture and Grazing Management in Western Oregon" discusses a number of best practices for pasture management. Consider reviewing this or other resources related to pasture management and evaluating whether your current management strategies are right for your pasture before investing time and money in renovating your pasture.
Have you assessed and addressed your pasture’s soil health?
Many pasture challenges can be addressed with careful attention to soil health and nutrient management. Most pasture species grow best in soils with a pH of 5.5-6.5 and proper nutrient management. If you have not conducted a soil test on your pasture within the last two years, this is a good place to start. "A Guide to Collecting Soil Samples for Farms and Gardens" provides information about how to collect a soil sample from your pasture for analysis, and "Nutrient Management for Pastures: Western Oregon and Western Washington" describes how to interpret the results of your soil test and adjust for any soil pH and nutrient issues in your pasture.
Overseeding best practices
If you’ve reviewed your pasture and soil health management practices and decided that overseeding is a good fit for your pasture, follow the recommendations below to improve the likelihood of successful overseeding.
Timing
In western Oregon, most pasture seeding occurs in September through mid-October. Ideally, overseeding will take place when soil temperatures are still warm and there is adequate soil moisture from rainfall to aid in germinating the seed. However, broadcasting in the spring, March to early April, is also an option if you are able to drive on the pasture without compacting the soil and there is no standing water. If you’re able to irrigate your pasture, you may choose to plant earlier in the fall or later in the spring.
Preparing the field
In preparation for overseeding it is important to manage the existing vegetation. Mowing or grazing the existing pasture species to 4” stubble height to reduce shading and competition for new seedlings is critical, as past research shows that shorter residue height leads to better establishment of overseeded species. You will also need to manage the weeds growing in your pasture before seeding. Ideally, this is done months in advance of overseeding so you can evaluate continuing weed pressure. Options for weed management ahead of overseeding include:
- Mowing or targeted grazing, depending on the weed species or if you manage your operation organically
- Using herbicides, when combined with improved management practices to limit the recurrent growth of weed species.
Management recommendations for specific weeds can be found in the "Pacific Northwest Weed Management Handbook" or by contacting your local OSU Extension office. For pasture preparation advice specific to organic methods or certified Organic operations, contact Oregon State University’s organic pasture & forage Extension specialist.
Species Selection
Species selection is key to success with any overseeding project in Oregon pastures. Species should be chosen based on a few crucial considerations:
- Nutritional value for your livestock.
- Suitability for your site’s soils and climate.
- Ease of establishment and ability to compete with existing grasses and weeds.
- Other benefits like improving soil health or wildlife habitat.
Legumes
Clover species offer a combination of benefits to animal nutrition and soil health, and are often relatively easy to establish. As legumes, clovers offer a consistent source of organic soil nitrogen, improving fertility — this is an enormous benefit to certified Organic operations or producers using organic production methods. The number and diversity of clover species also means that for every pasture, at least one clover species can be found that will likely establish well and thrive with proper management.
Most improved clover varieties have been developed in and for perennial pasture systems where their ability to compete or coexist with grasses is critical. As a result, many clovers can establish well when broadcast or drilled into thinning cool-season pastures. Clovers can also be perennial, biennial, annuals which will self-reseed with proper management, or annuals which will largely be gone after their lifespans are complete. This offers a great deal of flexibility for pasture planning and grazing rotation calendars.
White clover varieties (Trifolium repens) are the most numerous and the most widely-adapted, capable of growing in nearly any pasture.
Modern red clover (Trifolium pratense) varieties do best in reasonably well-drained pastures, and can fix more organic nitrogen than an equivalent stand of white clover. Older red clover varieties may reduce fertility in livestock due to secondary compounds in the plants which affect hormones, so be sure to get recently-bred varieties low in phytoestrogens.
Annual clovers such as subterranean clover (Trifolium subterraneum) for well-drained sites or balansa (Trifolium michelianum) and berseem (Trifolium alexandrinum) for more moisture-laden soils can offer significant boosts to productivity and livestock nutrition.
To explore more clover options, consult Oregon State University’s MatchClover app. Before buying, be sure to check if the clover seeds are coated. Many seed companies coat clover seeds — this can be positive for conventional growers but can risk delaying Organic certification for transitioning operations, or decertification for certified Organic operations. Also, be sure to inoculate clovers and any other legumes you are overseeding into pasture with their appropriate symbiotic Rhizobia species, as this inoculation is crucial for their establishment and nitrogen fixation.
Vetches (Vicia spp.) are another group of legumes that establish well from overseeding into western Oregon pastures. While their yield in pounds per acre will generally be lower than clovers in western Oregon, vetches are well-suited to hay production systems as their taller viny growth habit means they can be cut and cured more easily than many clover species. Though many vetches used for forage are annuals – such as hairy vetch (Vicia villosa) – vetches also persist readily in many pasture systems via self-reseeding with long-lived hard seeds.
Broadleaf, non-leguminous species
Plantain (Plantago lanceolata) and chicory (Cichorium intybus) are two species well-adapted to Oregon. Chances are you already have some wild local ecotypes in your yard or pasture. They establish readily in moderately and well-drained sites. Most farms or ranches will have little difficulty in getting them established by overseeding into existing pasture. However, these species have also been bred for improved forage value and yields — so along with their ease of establishment, you can plan on making your pastures more productive, diverse and palatable, adding a highly-digestible energy source to complement your grasses and clovers.
These species also have secondary health benefits for livestock. Chicory has been shown to reduce parasite loads in sheep, and also has antioxidants, which can improve animal health as well as meat quality. Plantain has been shown to reduce mild symptoms of bloat in livestock, and some research even indicates animals will self-medicate by seeking out plantain to eat if they are experiencing the onset of bloat. As such, both should be especially useful on farms and ranches managed with organic methods or under certified Organic standards, as they are organic forms of prophylactic animal care.
Small burnet (Sanguisorba minor) is another species that seems to establish well from overseeding in pastures in western Oregon. This species is drought-hardy, tolerant of frost, highly digestible and palatable for all classes of ruminants, and a perennial. Historically, it has been used for everything from land remediation after wildfire to pollinator habitat.
On well-drained hilly sites like those in the Coast Range, this species often does well. It also has some anecdotal success in central Oregon on private rangelands; however, it may be a bit too well-adapted to high-elevation rangelands, as a report from Wyoming suggests it can behave like an invasive species in those conditions. If you don’t have local knowledge of how small burnet performs in your region, starting with a small area to test its suitability to your property is the best approach.
Grasses
Based on research from comparable climates or with species we know will thrive in Oregon – as well as the experiences of local producers and agricultural professionals – a few species can be said to be safer bets than most.
Orchardgrass (Dactylis glomerata), annual ryegrass (Lolium multiflorum), and perennial ryegrass (Lolium perenne) can all be established in a pasture by overseeding. Orchardgrass does well in any western Oregon site that could be described as well-drained or moderately well-drained. As its name suggests, it can survive shading from nearby trees, shrubs, and other grasses quite well, making it adaptable, palatable and nutritious forage species for all classes of grazing animals.
Ryegrasses are also well-adapted to Oregon, with perennial ryegrass thriving in moist sites and providing excellent forage quality for ruminants (though its high non-structural carbohydrate levels may make it unsuitable for equines prone to pasture-associated laminitis). Annual ryegrass is more adaptable still, and also provides good forage quality. However, annual ryegrass will compete with your cool-season perennial forage species and should be used more as a stopgap measure to get quick groundcover over bare soil or a weedy area.
Another related option to consider would be, festulolium—a group of hybrids between the ryegrasses and tall and meadow fescue. These can confer some of the quick growth and palatability of the ryegrasses with the persistence of the fescues.
If you want to increase the density of grasses in your pasture and are happy with the grass species you already have, you can take the opportunity to purchase seeds of newer or complementary varieties of those species. A less reliable option is to let the field go fallow and hope that seeds from your existing pasture grasses will regenerate the stand — this option is less reliable though and could backfire if weedy species fill the gaps before your forage grasses. Additionally, lost time is lost grazing, which means that even fallowing a field in the hope it will regenerate is still a significant opportunity cost.
Adding new grass species entirely is another option Whatever you choose, know that the grass seedlings will have to compete directly with other grasses and weeds to get established. Depending on your pasture’s soils and climate, the species capable of that kind of competition will vary. Finally, no matter which species you pick, the pasture will need to be rested before you can expect new plants to take root enough to persist under animal grazing and hoof traffic.
Seed to soil contact
When overseeding, seeds need to be in direct contact with the soil, not on top of other vegetation. If the seed does not have enough contact with the soil it may dry out before it is able to establish the first root, the seminal root. Seeds may also be eaten by birds, including wild turkeys.
Often when overseeding, the seed is broadcasted on the field with a drop or rotary spreader or by hand for small areas. Harrowing, dragging or raking prior to broadcasting seed can help loosen the soil, then gently raking the seed into the soil will provide seed to soil contact. Most grass and legume species should be planted no deeper than ¼”; larger-seeded forbs can be seeded to a depth of ¼-¾."
You can also let animals do some of the work. Broadcasting seed then allowing livestock like sheep, goats or cattle to trample the seed into the soil may provide soil contact.
Some legumes like clover and grasses like orchardgrass and annual ryegrass can be frost seeded. This is when the seed is broadcast onto frozen soil in the late winter. The freezing and thawing cycles of soil will draw the seed into the ground.
When broadcast seeding, double the recommended seeding rate for drilling to allow for adequate coverage, seed loss, and seed that does not germinate because it is not in direct contact with the soil.
Another option for overseeding is using a no-till drill which is designed to overseed into an existing pasture in one pass, with little soil disturbance. It is a heavy seed drill with a specialized discs that cuts through vegetation. The drill places the seed, followed by wheels that press the soil back in place to cover the seed, creating seed to soil contact.
Resting the pasture
All of the species mentioned above have one thing in common: they will need you to rest your pasture for a time before they can establish themselves enough to be useful to you.
Annual species may need a shorter time to grow at the start. However, if you want them to reseed, they will require long enough rest at the end of the growing season to flower and make seeds.
Perennial species usually take a longer time to get fully established—often at least one or two growing seasons. For example, if you overseed in early spring, let the pasture rest for the season until fall or even spring the following year, depending on how successful the overseeding seems to be.
If you buy seeds and put the work into getting them on the pasture, you will have wasted time and money if you never give the plants a chance to get their roots under them to be resilient to stresses like grazing and trampling. The less time they have to get established, the higher the mortality rate will be on your newly-seeded plants. As such, the trade off is you can either rest the pasture and have more successful overseeding but a short-term reduction of grazeable acres, or you can graze the pasture sooner after reseeding and ultimately get less forage per dollar or pound of seed than you otherwise would have. Which of these options is most appropriate will depend on your situation, but generally it is best to err on the side of resting the pasture and letting new seedlings get established.
Once the newly planted pasture is green and growing, you may be tempted to let your livestock start grazing. However, grazing should be deferred until seedlings are well established. Young seedlings are developing their root systems and building energy reserves for future growth. If the soil is moist and the root system is still weak, animals will pull the new plants out of the ground when grazing.
One way to determine if the pasture is ready for grazing is to give individual plants a test by pulling on them swiftly upward from the base of the plant, just as an animal might when grazing. If you pull it out, do not let animals graze. If the plant stays rooted when you pull on it, then you can consider letting your livestock graze for short periods of time. Be careful not to allow livestock to overgraze the pasture. You will generally want to maintain a stubble height between 4 and 10 inches.
For experienced grazers who are able to control the stocking density of their herds, consider the benefits of modulating grazing intensity to help limit the competition provided by the existing vegetation and help recruit seedlings into the sward. A short bout of high-intensity stocking, sometimes called “flash” grazing, can remove canopy of vegetation from above the new seedlings and reducing the competition of the existing vegetation. However, if livestock begin to defoliate newly seeded plants before they are fully established, those plants can die or be pull from the ground.
Conclusion
Overseeding can be a great option for pasture renovation when carefully planned according to the principles above and combined with appropriate soil and grazing management practices. As always, if you have any questions about overseeding your pasture, ask an expert through Ask Extension.
