University of Minnesota Beef Team
The 2010 growing season is just around the corner. Now might be a good time to think about things we could do to make our pastures as productive as possible.
We've heard in winter meetings and read articles stating that feeding cattle is the single most expensive component in beef cow/calf production systems. Having cattle feed themselves costs about one-third as much as providing them stored feed. So getting the most out of our grazing systems should be our number one priority.
While grazing systems have many components, including adequate fencing, available water and moving cattle, pasture renovation will be the focus of this article.
Many of us are familiar with old pastures that seem to produce some green forage, but just do not seem to hold up to grazing conditions or produce forage for very long. It is important to note that pastures do decline in productivity over time, and it is a process that can be avoided. This question frequently comes up: is pasture renovation worth it? The answer is: only if we want to make more money.
The majority of articles ever written on pasture renovation start off by saying that the most essential step is the development of a plan well ahead of the actual renovation, similar to having a road map to guide us to where we want to go.
A critical part of the renovation plan is a soil test, so that we are confident the new plants we seed have the best chance to thrive. A soil test not only tells us the nutrients needed, but also illustrates what can be seeded, based on the soil pH, or acidity. For most pasture crops, the ideal pH ranges are as follows:
Grass pastures 5.6-6.2
Legume pastures 6.0-6.6
Alfalfa pastures 6.4-7.0
Traditional agricultural limestone takes about six months to raise soil pH, however in many areas there are by-product limes available that do the job much more quickly.
Deciding on which species to plant is another component of the renovation plan. If possible, seeding mixtures of grasses and legumes has several advantages. Legumes can fix nitrogen for the grass component, eliminating the addition of nitrogen fertilizer.
Table 1 illustrates the economic advantage of seeding legumes with grass. In Minnesota, cost of forage produced when legumes supplied the nitrogen was less than half the cost when nitrogen fertilizer was used. Also, legumes tend to be more productive than grasses during the warmer and drier growing conditions in summer, so seasonal forage yield of grass/legume mixtures is more evenly distributed throughout the growing season than monocultures.
And probably the best reason to graze a mixture of grasses and legumes is im-proved animal performance (Table 2).
In Illinois, conception rate and daily gain of cows and calves grazing a mixture of tall fescue and red clover were superior to gains on fertilized grass alone.
Alfalfa is likely the preferred legume for pastures with the right soil pH. Of the cool-season legumes adapted to the north central U.S., alfalfa has the best combination of forage yield, vigor and persistence. Alfalfa combines well with many grasses, but especially well with sod -forming types such as low-alkaloid reed canarygrass or fescues.
When soil pH will not support alfalfa, red clover is a very productive legume, but is not as persistent due to susceptibility to disease. Because red clover is very vigorous, it should be seeded with a vigorous grass, such as orchardgrass or timothy. Other legume options include birdsfoot trefoil, which is not as productive as alfalfa or red clover but is the legume of choice for stockpiling; and kura clover, which is slow getting started, but very persistent and nutritious once established.
Selecting species adapted not only to the growing conditions but also the establishment method is fundamental to renovation success. The less vigorous legumes and grasses are challenging to establish into existing sod. A good reference in choosing forage species, varieties within species and seeding rates is the Minnesota Varietal Trials Results, available from the University of Minnesota Extension, or online at www.maes.umn.edu.
Seedbed preparation is a critical step in any pasture renovation program. One of the key principles here is placing the seeds in an environment where they have the best chance to thrive. Seeds of species commonly used in pastures are small, so they need to be planted just deep enough to remain moist, yet shallow enough to enable emergence.
A seeding depth of about one-quarter inch is ideal in most cases. Another key factor at seeding time is controlling competition from the existing sod until the new seedlings are established. Conventional tillage to prepare a good “garden seedbed” will usually offer the best chance of successful pasture establishment, and offers the potential to in-corporate lime.
Seeds can be planted in a smooth, firm seedbed and existing sod has been thoroughly tilled. Conventional tillage is, however, the most time consuming and costly seedbed preparation method, so may not be practical in many situations.
No-till seeding has the potential to be successful in many pasture renovation situations, but requires more attention to detail. Because no-till seeding does not disturb the sod, it is especially important to suppress the sod shortly before or after seeding, before germination has begun.
Glyphosate herbicide is a flexible management tool in no-till seedings because varying the application rate can be used for different situations. If the goal is to kill the existing sod and introduce completely new species, a higher glyphosate application rate can accomplish this. If the goal is to introduce some new species while keeping the current ones, such as introducing a legume into grass, a suppression rate of glyphosate can be used.
Some publications that talk about pasture renovation suggest that overgrazing can be used to manage competition during seedling establishment. Using grazing as a sod-suppressor will require advanced planning.
Pasture renovations have the best chance of success under good growing conditions, but obviously the existing sod will be the most competitive at those same times. Quite likely, several overgrazing cycles are needed to weaken the existing sod.
Two possible scenarios are overgrazing in late summer and fall followed by a spring seeding, or overgrazing all spring and summer followed by an early fall seeding. With no-till seeding, it is critical to get good seed to soil contact and seed placement at the right depth, so some type of drill to accomplish these goals is desirable.
Simply broadcasting seed on the soil surface will usually not result in successful stand establishment. A general rule when using drills to interseed is that if a little seed cannot be seen beside the drill slit, then the seeding depth is too deep.
Minimum tillage may be one of the most useful seedbed preparation types for many pasture renovation situations. Minimum tillage is accomplished by disturbing forty to sixty percent of an established sod. This can be done using a disc, field cultivator or other tillage equipment.
Tillage helps to suppress the sod, expose bare soil and break up manure pats. Seeding can be done either with a drill, as in the no-till system, or broadcast onto the surface followed by dragging and/or cultipacking.
An idea that is gaining popularity in pasture renovation is the use of a “break crop” before establishing a totally new pasture. Most producers don't want to have any down time between taking out their old pasture and establishing a new one. By no-till drilling or broadcasting onto a lightly disced pasture a producer can establish a productive, high quality forage source in 50 to 60 days. Common species used as a break crop are annuals that germinate quickly and are well suited to interseeding or minimum tillage. These highly competitive annuals provide forage while shading out the old pasture sod so that following the annual crop, the producer essentially has a blank seedbed in which to establish permanent pasture species.
At the University of Minnesota North Central Research and Outreach Center in Grand Rapids, annual ryegrass has been used successfully as a break crop in several pasture renovations, ranging from conventional seedbed preparation to no-till with glyphosate. Annual forage production has been in the range of four tons of dry matter per year.
Because annual ryegrass does not go dormant in fall and stockpiles well, it has been useful in extending our grazing season into late November and even December for the last three years. Following annual ryegrass, pastures have been successfully seeded to a mixture of alfalfa with either reed ca-narygrass or meadow fescue.
Start pasture renovation with a written plan, not just an idea. Check with your seed dealer or university Extension agent when choosing what to plant. Be patient, and use good management to help new forage seedlings become established. Avoid overgrazing and schedule routine rest periods between grazings.
Try to take good records, possibly even some pictures. It's sometimes hard to remember how things looked before changes were made. And keep in mind that pasture renovation is a process, not an event.