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Smooth Bromegrass (Bromus inermis)
From Montana Interagency Plant Materials Handbook *
By S. Smoliak, R.L. Ditterline, J.D. Scheetz, L.K. Holzworth, J.R. Sims, L.E. Wiesner, D.E. Baldridge, and G.L. Tibke
Smooth bromegrass is a rapid-developing, long-lived, sod-forming, introduced grass with good seedling vigor and subject to "sod-binding." Smooth bromegrass is the most widely grown of the cultivated bromegrasses. This grass has been cultivated since its first introduction into the United States in the 1880's.
Bromegrass varieties may be divided into two groups, "northern" and "southern"'. The northern type is believed to have its origin in Russia, and the southern in Hungary. The varieties in each group have certain characteristics in common:
Northern Type Southern Type
1. Spring growth is later 1. Begin growing earlier in Spring
2. Weakly rhizomatous 2. Strongly rhizomatous
3. Leaves well up on the stem 3. Leaves tend to be basal
4. Best seed producers 4. Poorer seed producers
5. Seedlings less vigorous 5. Seedlings more vigorous
6. Sod bind less rapidly 6. Sod bind rapidly
7. Better recovery after cutting 7. Poorer recovery after cutting
and grazing and grazing
8. Less drought resistance 8. Better drought resistance
9. Grows better with alfalfa 9. Does not grow as well with
mixtures alfalfa mixtures
The northern type is recommended for use in irrigated hay and pasture. It spreads less rapidly and has less tendency to crowd legumes out of a mixture. Summer and fall regrowth is better than with southern types. The southern type is recommended for dryland. It has good drought tolerance and provides good ground cover.
The variety 'Manchar' is intermediate between the two types and incorporates the desirable characteristics of the southern and northern types.
Smooth bromegrass is a long-lived, sod-forming perennial. It develops a deep root system which accounts in part for its tolerance to drought and heat. Stems are generally 2 to 4 feet long, but only half the tillers produce stems. It is a cool-season grass that produces leafy, vegetative growth early in the season and stems with large panicles in early summer.
Bromegrass seedlings may be identified by their long, narrow, hairy leaves, which usually are gently twisted in a clockwise direction. As the plant becomes older, the first of lower leaf sheaths wither and die; the new leaves are broader and less hairy. A slight growth constriction may occur on these leaves, forming a configuration resembling an "M" or a "W." This characteristic, however, is not always evident. One of the characteristics of this grass is the rapidity with which it becomes "sod-bound."
Smooth bromegrass is adapted to a wide range of soil and moisture conditions, but is suited to the more productive soils. All of the major soil types in the region to which bromegrass is adapted are suitable for bromegrass. The best soils are the deep silt loams, but bromegrass also does well on light, sandy soils. Since it requires a readily available supply of nitrogen, the soil should be fertile. Soils low in nitrogen may need a heavy application of nitrogen fertilizer. Bromegrass possesses some degree of tolerance to alkali, but is surpassed by western wheatgrass in this respect. Short periods of flooding are withstood in a satisfactory manner and the grass will emerge through a considerable deposition of silt. It is adapted to both dryland and irrigation.
In terms of persistence, smooth bromegrass is one of the more drought tolerant, introduced species in common use in Montana. In dry years it will be exceeded in yield by a number of other species including crested and Siberian wheatgrass, and Russian and Altai wildrye. It should be grown on dryland only in areas receiving more than 14 inches average annual precipitation. While it does not withstand extreme drought conditions, it survives some drought and extremes of temperature. It is winterhardy. In dry summer periods, it becomes dormant until the return of cool, short days and fall moisture. It is somewhat tolerant of salinity and acidity. It has wide adaptation for pasture, hay and erosion control in many areas of the United States. It has been grown successfully at altitudes in excess of 9,000 feet in Montana.
Smooth bromegrass has escaped from cultivation to range and meadowlands in mountainous areas of Montana such as western Glacier, Pondera and Teton counties near Glacier Park. When seeded in complex mixtures in this general area, this grass will usually take over within very few years.
Smooth bromegrass has several short-comings. Long, narrow seeds, which bridge in conventional seed drills, make it difficult to plant. Once established, full yields are frequently not reached until the second or third year of production. As the stand matures, the continued growth of rhizomes increases tillering until the stand becomes very dense and unproductive. The vigorous rhizomes also make it difficult to eradicate a stand by cultivation. This forage requires fairly good internal soil drainage, although it will tolerate about two weeks of flooding in spring before growth begins, but none during the growing season. It does not normally perform well in areas of excessive rainfall unless it is well fertilized. Diseases are not a major problem, although it is susceptible to winter crown and root rot.
Use for Hay
This high-yielding grass is best suited to hay production. The grass grows tall and erect and the stems are leafy, making it a good crop for haying. Although it is very aggressive in a mixture, its tendency to establish itself slowly and its high nitrogen requirement make it well suited for use in mixtures with alfalfa. It should be managed so as to maintain the alfalfa in the mixture. Yields of hay from this mixture are often three times those from bromegrass alone. Properly nodulated alfalfa provides it with the much needed nitrogen.
Bromegrass is high in protein compared to other grasses at similar stages of maturity, especially timothy. However, it is low in energy while timothy is high. These differences in quality are normally less important than total production, however, and the choice between timothy and bromegrass can normally be made on the basis of dry matter yield.
Heavy applications of fertilizer can maintain
good yields of bromegrass for up to 10 years. It is frequently economical to
apply nitrogen since this grass is most responsive to fertilizer. The
application of nitrogen generally reduces sod-bound conditions since a good
supply of nutrients permits a high number of shoots to grow. Mechanical
renovation and application of fertilizer at the same time is often used.
Regrowth after hay cutting is generally low in yield. Very early haying and the use of adequate amounts of fertilizer do extend the season of growth and increase second growth yields. Bromegrass forage remaining after seed harvest may be pastured or cut for very good quality hay.
Use for Pasture
Smooth bromegrass is commonly used for pasture. Spring growth is early. Young plants are very leafy and palatable. Vigorous rhizomes produce a dense sod and make this grass fairly resistant to elimination by overgrazing. However, smooth bromegrass has many weaknesses when used as pasture. Plant growth occurs mainly in the spring and early summer so there is a flush of growth followed by a long period of slow growth. To compound this problem smooth bromegrass is tall growing and almost all leaves required for future growth are within the bite level of grazing livestock. It must be grazed lightly early in the season to let growth accumulate for use later in the season. Also, in late summer and fall when the herd sizes are largest, much more pasture area is required and careful rotation of pastures is necessary to maintain adequate growth. Do not graze the new pasture seeding, cut the first crop for hay. Best production will be obtained if the pasture is divided into units and a rotation grazing system used. Allow about 28 days regrowth period and allow the pasture to dry sufficiently after irrigation to prevent damage by trampling.
Smooth bromegrass seed production is good with 500 plus pounds production on irrigated land and 200 to 500 pounds on dryland. Bromegrass seed is ready to be combined when the lower branches of the panicles have lost their green color. The stems will begin to dry and turn brown from the top down. The earlier maturing spikelets may begin to shatter.
* The Montana
Interagency Plant Materials Handbook (EB69)
is no longer in print, but is available for viewing in
Montana County Extension Service and National Resource Conservation Service Offices.