Richard Taylor, Extension Agronomist; rtaylor@udel.edu
I have received several requests over the past several weeks concerning overseeding or renovating pasture and hay fields and feel it’s a good time to begin a discussion on the process. All too often, we find ourselves moving into mid to late fall without having taken the time to really consider all decisions that have to go into improving the odds that the planting will be successful. You need to keep in mind that seed costs alone can equate to a hundred dollar an acre investment; and, if we really take into account all the variable costs, that new pasture or hay field can easily represent an investment of hundreds of dollars per acre.
So in the pre-planning process, what’s first? I know many get tired of hearing the phrase but testing the fertility of your soil far ahead of time is still the number one issue. If the field will not be tilled and you have not been applying significant quantities of commercial nitrogen (N) fertilizer to the field, sample at 0 to 4 inches deep in each field or management zone (an area of the field treated in a similar fashion and not much different from other areas of the field in soil type).
If you have used large quantities of commercial N fertilizer in the past, you really should take both a 0-2 inch depth sample for determining the soil acidity in the upper soil layer as well as a 0 to 4 inch depth sample for nutrient content (phosphorus, potassium, calcium, magnesium and other essential elements).
The reason for this distinction is that the ammonium or urea N forms that we apply as fertilizer are converted by soil bacteria into nitrate and in the process acidity is released into the soil. Since the N is all surface applied, the release of acidity near the soil surface can create a condition known as ‘acid roof’ where the top inch or two of soil is much more acidic than the deeper layers of soil. A second reason involves the very slow movement of limestone down through the soil. Studies on pastures in Connecticut many decades ago showed that lime moves at a rate of about 1 inch per year so it takes a very long time to have an impact on the entire rooting zone of forage grass and legume plants.
For fields that will be tilled and a new planting established, the traditional plow layer sample (0 to 8 inches) for both soil pH (acidity) and essential nutrient status will be the correct choice. If the soil sample indicates that the soil must be limed, apply the recommended amount of limestone and work it into the soil as soon as possible to allow time for the limestone to neutralize soil acidity before planting time. Although, if it remains dry, lime may not completely react, and a second soil test still would be useful to determine if any additional lime will be needed. Additional agricultural lime and the recommended phosphorus (P) and potassium (K) and any other needed nutrients can be applied and worked into the soil shortly before planting the field.
Everyone asks the question of whether to apply N at the time you plant a new field or seed a field you are renovating. My preference is that you should wait until the new grass is several inches tall and has enough biomass and roots to compete for the applied N and to store any extra N for future growth. Until forage plants have enough leaf area to rapidly capture the sun’s energy and convert it into more plant tissue or into sugars for storage, weeds in new plantings or the current vegetation in renovations are likely to outcompete the new seedlings for N and then for light, water, and other nutrients. When waiting to apply N although weeds and current vegetation will still be present, the new seedlings will at least be in a better competitive position when the N is finally available to stimulate growth.
Now that you’ve taken care of any soil fertility issues that can reduce the chance for a successful stand, the next decision involves choosing the right seed to plant. I’ve had the opportunity over the years to read many seed labels on various pasture mixes offered for sale. I understand the convenience of buying a prepared pasture mix and the allure of these mixes. The buyer often assumes that the seller has spent the time and energy studying the issue and has come up with a mixture that in their opinion and experience has the best chance of success. I certainly can’t speak to motivation of the seller but keep in mind that from a business point of view, seed that is mixed and offered for sale need to be sold over as large an area as possible to justify the expense of wholesaling large quantities of seed, blending, packaging, and labeling the seed. In my opinion, this nullifies the expectation that the seller has designed the mix for your particular field or location.
After looking at the species of forages used in the prepared pasture mixes, I find that these mixes are more like a shotgun approach to seeding where you plant a little of everything in hopes that something will establish in all areas of the field. Usually they contain a quick establishing grass such as ryegrass that can germinate in as little as 5 to 7 days so the buyer can feel comfortable with the new seeding. The mixes also usually contain the feel-good or highly recognized grasses such as timothy and Kentucky bluegrass in horse pasture mixes and at least some orchardgrass and probably an endophyte-free tall fescue to provide more permanent cover. Finally, a legume such as white or ladino clover, red clover, or alsike clover will be in a pasture mix to provide the N-fixing legume everyone would like in a pasture.
The convenience of these mixtures comes from not having to mix them yourself before you fill the seed drill and the allure comes from not having to make a decision other than how much seed per acre to plant and not having to choose individual species to plant. For most buyers, the convenience and allure end up costing them many, many dollars per acre in seed costs for seed of grasses that won’t survive in grazing situations or won’t survive more than a season or two at best or will be unproductive for much of the grazing season.
So what should you do? I prefer going with a simpler mixture using forage species that are adapted to our region. In most cases, the only species that will survive for many years in our transitional zone climate is tall fescue. Because of endophyte (an fungus growing in some tall fescue plants) issues, many growers have tried the endophyte-free tall fescue varieties and some have had success with keeping a stand for many years while others have seed stands decline or disappear quickly. The newest chapter in this issue has been the development of novel or friendly endophyte tall fescue varieties. The novel endophyte tall fescue varieties do not produce the chemical compound (alkaloids) that interfere with animal performance but still provide benefits to the tall fescue plants helping them survive in many stressful environments. A limitation still in evidence with these new tall fescue varieties is that horse owners who breed horses do not all accept tall fescue as a feed source for their animals. This limits tall fescue’s acceptance.
What other species can you include in your simple mixture? Orchardgrass is another grass that many producers like to include in a pasture mixture but you should be aware that many orchardgrass fields are failing due to a disease/insect/environment/management complex interaction we’ve been calling orchardgrass decline. If you choose to include orchardgrass, keep it as a small proportion of your mixture. The other grass to include at least on the heavier soils is Kentucky bluegrass. Be sure to include several varieties of the Kentucky bluegrass to help with disease resistance. It will be most productive early in the year (early spring to early summer) and mid- to late-fall. Finally, add in a legume to help with providing N for the grass to use as well as to improve the protein and forage digestibility of the pasture. For grazing, most people prefer a ladino-type of white clover. Although slobbers (the animal produces excessive amounts of saliva) is a potential concern with all clovers, it seems to be mostly associated with red clover. Often included in commercially sold horse pasture mixtures, alsike clover is known to cause photosensitivity (sunburn) especially in horses and should not be included in your pasture mix.
You will find it useful to talk to your seed dealer about the various varieties of each species that are available. Once you decide on the varieties to use and you purchase seed, you can mix your own pasture mix by either purchasing or renting a cement mixer and combining the seed in the proportions you decide are best for your purpose and field. Since many legumes now come pre-inoculated with the N-fixing bacteria and often are coated with a fine limestone, do not over mix the seed and when you re-bag it store it where it is protected from high temperatures and humidity. Stored properly, the seed can be held over the winter if something prevents you from seeding this fall but you should plan to plant as soon as possible after purchasing seed. Not only are the N-fixing bacteria alive; but, if you use a novel endophyte tall fescue variety, the endophyte has a limited storage time (around a year under good conditions) before it should be planted. Although the tall fescue seed will germinate after longer storage times, the endophyte fungus may no longer be alive. The fungus only lives in the plant and is not soil-borne.
Next time, I’ll cover some of the other management issues to consider, such as planting date.
The other articles in this series are:
Thinking of Renovating or Planting a New Pasture or Hay Field? Part 2: Planning to Planting