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Developing Alfalfa Adapted to Grazing in the Northern Great Plains

By John Berdahl , Forage Geneticist, Northern Great Plains Research Laboratory, Mandan, ND


Beef and dairy producers have long recognized the high feed value of alfalfa in mixed grass-alfalfa pastures. Two major problems, bloat and lack of plant persistence, have held back more widespread use of alfalfa in pastures. Development of a bloat-safe alfalfa will likely depend on use of new biotechnology methods that would enable alfalfa to produce tannins. Tannins are chemical compounds that slow the rate of protein digestion in the rumen, which in turn decreases rumen foam associated with poor release of fermentation gases. Bloat-safe legumes such as sanfoin contain moderate concentrations of tannins.

Improving the longevity of alfalfa for grazing is a less complex problem. Yellow-flowered alfalfa, a separate species that is closely related to our common purple-flowered alfalfa, has always had superior survival in our grazing trials. Yellow-flowered alfalfa is characterized by high levels of plant dormancy that enable stands to survive extended dry and cold periods that occur in the Northern Great Plains. Yellow-flowered alfalfa has a deep-set crown that protects plants from trampling along with numerous, active crown buds that result in production of new stems and a broad crown area. Their root system is fibrous, in contrast to the tap-root of purple-flowered alfalfa. It is possible to incorporate a spreading trait into plants that have a fibrous root system. Low seed production is the primary drawback of yellow-flowered alfalfa that has prevented more widespread use of the species. Plants have a small, sickle-shaped seed pod that shatters easily when ripe. In our alfalfa breeding program, we are crossing yellow- and purple- flowered types in an attempt to improve seed production but maintain the superior survival of yellow-flowered alfalfa. The high levels of dormancy found in yellow-flowered alfalfa reduce regrowth potential during years when mid- and late-season moisture is available. Alfalfa cultivars with relatively high levels of dormancy still produce high first-cut yields. Several dual-purpose pasture/hay type alfalfa cultivars have been developed (Table 1), and their first-cut hay yields are at least as high as cultivars such as Vernal that were developed primarily for hay. Our objective is to develop cultivars with higher levels of dormancy than those listed in Table 1. We believe that high levels of dormancy will provide an extra measure of hardiness that is needed for long-term survival under grazing.

 

Table 1. Single-cut hay yields of pasture- and hay-type alfalfa cultivars at the Central Grasslands Research Extension Center in 1999.
Cultivar Primary use Dormancy class Hay yield
    (1 = most dormant) (tons/acre)

Travois

Rambler

Roamer

Ladak 65

Spredor 3

Vernal

Rangelander

Alfagraze

Pasture

Pasture

Pasture

Hay

Pasture

Hay

Pasture

Pasture

1

1

1

1

1

2

1

2

3.0

2.9

2.8

2.6

2.6

2.5

2.4

2.3

5% lsd     0.3

 


Dr. John Berdahl
Northern Great Plains Research
PO Box 459
Mandan, ND 58554-0459
Phone: 701-667-3004
E-mail: BERDAHLJ@mandan.ars.usda.gov


NDSU Central Grasslands Research Extension Center

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