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Characteristics of Prairie Grass

Prairie grass (Bromus Wildenowii Kunth.) is a tall growing perennial grass that is suited to well drained soils with medium to high fertility levels and a pH of 6.0 or greater. It is a type of bromegrass, but is different from smooth bromegrass in that it does not have rhizomes and it produces seed heads in each growth period, especially during the summer. Herbage and immature seedheads of prairie grass are highly palatable.

Prairie grass is more drought resistant and continues to grow later in the fall than most cool-season forage grasses. Fall harvesting improves the winter persistence of prairie grass. It will persist for 4 to 6 years in Pennsylvania if properly managed. It matures about the same time or a little later in the spring than orchardgrass. Forage quality of prairie grass compares well with other cool-season grasses but is more palatable. It is an excellent grass for providing forage during droughts and for extending the grazing season well into the fall in Pennsylvania.

Prairie grass is occasionally refered to as rescue grass (Bromus catharticus Vahl). While these grasses are related, they are not the same and rescue grass is less persistent than prairie grass in Pennsylvania's climate.


Adapted Prairie Grass Varieties

'Matua' is the only cultivar of prairie grass that is currently sold in the U.S.. This variety was developed in New Zealand under grazing conditions and has been very productive in Pennsylvania. Other prairie grass varieties are being evaluated by the USDA-Pasture Laboratory and Penn State University for persistence and productivity; however, none of these varieties are commercially marketed in Pennsylvania at this time.


Prairie Grass Establishment

Prairie grass is slower to emerge after seeding than either tall fescue or smooth bromegrass. However, prairie grass growth and development after emergence is greater than either of those grasses. A moist, firm seedbed is required for prairie grass or prairie grass-legume mixtures. Spring or summer seeding of prairie grass are recommended in Pennsylvania. However summer seedings should be completed by early August in the northern half of the state and by mid August in the lower half of the state. Later seedings are generally inadequately established to survive Pennsylvania winters.

Seed may be either drilled or broadcast. Drilling is preferred because it provides a more uniform depth of planting. Plant prairie grass seeds 1/4 inch deep. Although prairie grass seed sold in the United States has generally had the awn removed, the long fluffy seeds often bridge in conventional seed drills and make planting difficult. Using one of the alternate seeding methods listed will help reduce this problem: 1) mix prairie grass seed with a small amount of triple superphosphate and sow through the fertilizer attachment of the grain drill, or 2) mix prairie grass seed with a small amount of oats and sow through the small grain attachment of your grain drill (only for spring seeding).

Most hopper-type fertilizer spreaders can be calibrated to broadcast prairie grass seed. If seed is broadcast, however, be sure to lightly cover the seed with soil. This can be done by light disking or by following with a drag or harrow. Unlike many other cool-season grasses, prairie grass should not be cultipacked after seeding because it increases the difficulty of seedling emergence and the risk of stand failure.

Prairie grass seeding rate varies with seedbed condition, method of seeding, and quality of seed. Generally, when seeding prairie grass alone, rates of 30 to 35 lb per acre are sufficient. When seeding in mixtures with a legume, seeding rates of 20 to 30 lb per acre of prairie grass are recommended. Germination of stored seed can decline rapidly, therefore seed should be used promptly and not stored from year to year.

Weed control at the time of seeding and during prairie grass establishment is extremely important because of prairie grass's slow emergence and upright growth. The upright growth allows emerging weeds below the prairie grass to receive sufficient sunlight to continue growing. If weeds are anticipated (previous weed problem) in a field to be seeded to prairie grass, use of a preplant or preemergence herbicide is recommended. Refer to the most recent edition of the Penn State Agronomy Guide for efficacy and use restrictions of herbicides labeled for use during and after forage grass establishment.


Prairie Grass Harvest Management

After spring seeding, prairie grass can be grazed after 50 to 70 days or harvested for hay after 80 to 110 days, depending on climatic conditions. Grazing the initial harvest after spring seeding will stimulate the formation and development of new shoots. Even though prairie grass roots develop faster than smooth bromegrass or tall fescue roots, make sure the grazing animals do not pull the young plants out of the ground.

If the seedling growth of prairie grass is harvested for silage or hay, fewer new shoots will develop and the stand will have reduced ground cover and a bunch type appearance. Prairie grass yield from the first harvest after seeding will be similar to that from smooth bromegrass but less than that from tall fescue. Grazing in the fall after a summer seeding is not recommended.

In established prairie grass stands, delaying the first spring harvest will reduce recovery rate and lower the yield potential of the next cutting. Under normal weather conditions, about 25 to 30 days of regrowth is sufficient between harvests. This period is a good balance between yield and quality of prairie grass. Generally, by this time new shoots have developed at the base of the plant and harvesting or grazing will allow more light to reach the shoots and stimulate their growth. A growth period of approximately 50 days in mid-summer will allow the prairie grass seed heads to mature and drop seed during August. This will thicken up the stand the following year.

Prairie grass's ability to grow at cool temperatures makes it ideal for late fall or early spring grazing. Fall yields of nearly 3.5 tons per acre are possible. It persists best when managed so that monthly harvests are made during the fall. In addition, spring yield and shoot density increase when multiple harvests are made in the fall. Harvesting only once in the fall (November) caused 98 percent of the of the basal shoots (source for growth the following spring) to winter kill. However, when prairie grass was harvested or grazed 3 times during the fall only 35 percent of the basal shoots winter killed. Compromise is needed with regard to fall harvesting because late fall grazing will slightly reduce prairie grass vigor the following spring and restrict its use as an early spring grazing source.

Prairie grass should not be cut or grazed below a 3 inch stubble height because regrowth energy reserves and buds for plant regrowth are contained in this region. Cutting or grazing below this height will weaken the plant and delay regrowth. Yields of nearly 7 tons per acre have been achieved when harvesting prairie grass for silage.

Prairie grass is an ideal grass for grazing systems because of its potential for early spring and fall growth. Its spring growth offers the opportunity for earlier spring grazing and its fall growth can effectively extend the grazing season by as much as two months over traditional cool- season grass species. In addition, since seed heads are palatable, it is not necessary to mow off the seed heads that remain after grazing.

Prairie grass persists better under rotational grazing than continuous grazing management. It will not withstand overgrazing, especially when it is under stress of excessively wet or dry conditions.

The quality of prairie grass is not as strongly affected by time of harvest as other cool-season grasses. Digestible dry matter intake (DDMI) is greater for Matua prairie grass than orchardgrass. When harvested on May 21, Matua had 25 percent greater DDMI than orchardgrass. This difference increased to 35 percent when harvesting one week later. Prairie grass may contain lower levels of trace elements than other grasses. Inclusion of a legume in the mixture with prairie grass, or providing trace elements to animals consuming primarily prairie grass will eliminate potential problems.


Prairie Grass Fertility

Fertility needs at seeding should be determined by soil test. Soil pH between 6.0 and 7.0 is best for prairie grass, however it is adapted to slightly alkaline or acid soils. In the absence of a soil test, assuming a medium-fertility soil, plow down 0- 45-135 lb. per acre and apply 20-20-20 lb. per acre at seeding (banded if possible). If prairie grass is seeded with a legume, reduce or eliminate nitrogen application at seeding.

Prairie grass requires a high level of fertility for maximum production. It is also very responsive to N fertilization. If prairie grass is planted with alfalfa or another legume, restrict annual N applications to 40 or 50 lb. per acre to limit the effect N has on reducing nitrogen fixation of the legume. If prairie grass is grown without a legume, apply 100 to 200 lbs N per acre in split applications of 50 lbs per acre in early spring when the grass becomes green and 50 lbs per acre after each harvest and in early fall. Adequate nitrogen fertilization is essential for maximizing prairie grass growth in the fall.


Prairie Grass Summary

Prairie grass is a deep-rooted grass which grows best on fertile, well-drained soils. It will provide early spring growth and excellent fall growth to extend the grazing season. Matua, the only variety of prairie grass currently sold in Pennsylvania, is a good cool-season grass for Pennsylvania conditions. However, proper management is essential to obtain adequate yield and persistence.


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This page was last updated on November 16, 2002