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Yellow-flowered alfalfa

Written by Robert W. Drown Published on 09 Apr 2009


Plant description
Yellow-flowered alfalfa is a perennial legume growing up to 30 inches high with multiple erect stems.

It has alternate sets of three oval-shaped, hairy leaflets with yellow flowers 0.25 to 0.5 inches in diameter.

Yellow-flowered alfalfa is truly an amazing plant. Stands of it have survived in northwest South Dakota for over 90 years under stresses of drought, cold, grasshoppers, grass competition and livestock grazing. It is capable of reseeding itself in rangeland and protecting itself by going dormant in dry times. If a late rain occurs during drought years it will re-grow, blossom and set seed in a hurry.

Most alfalfa varieties have a long main taproot that grows deep into the soil. Yellow-flowered alfalfa has a fibrous root system that is unlike other alfalfas and is similar to the roots of grasses, allowing it to compete with grasses and forbs for moisture.

Yellow alfalfa (Medicago falcata) commonly hybridizes with other common alfalfa (Medicago sativa), producing alfalfa plants that are intermediate in growth habit, seed pods and flower color. Common alfalfa has purple flowers and spiral- shaped seed pods, and yellow-flowered alfalfa has sickle-shaped seed pods.

Origin and history
Alfalfa evolved in the Middle East and central and northern Asia regions with cold winters and hot, dry summers. Over the last 100 years alfalfa has been planted on millions of acres, and more than 100 varieties have been developed in North America. It very rarely has become naturalized on rangelands.

Yellow-flowered alfalfa has a natural range in Siberia that is climatically similar to the Northern Great Plains. It is more drought- tolerant, winter-hardy and tolerates grazing better than common alfalfa, thanks to its deep-set crown and fibrous root system.

Bud Smith of Lodgepole, South Dakota, began his lifelong interest in yellow-flowered alfalfa (falcata) in the early 1960s. He had attended a crop improvement meeting in Bison and learned about the history of it and how an early South Dakota State College Professor, N. E. Hansen, had sent out packets of seed in 1915 to several dozen early settlers, including Bud’s uncle Charles Smith, and told them to throw it out of their back door.

Dr. Hansen had made eight trips to Europe and Asia beginning in 1894 in search of plants that had the potential to benefit agriculture in the Northern Great Plains. He collected seed from yellow-flowered alfalfa plants he found growing wild in Siberia, an area very similar in soils and climate to western South Dakota.

Interseeding and natural spread
In the 1960s the Smiths started grazing the original rangeland of their uncle that had been interseeded to yellow-flowered alfalfa in 1915. They noticed several patches that had a lot of seed, so they took the cattle off to encourage greater seed production, which they harvested in the autumn. They grazed the site with sheep and cattle and found that they had no problem with bloat. Then the idea germinated in Bud’s mind to gather seed from those sites and interseed other grazing lands on his ranch. In order to increase seed production Bud started working with leaf-cutter bees, efficient pollinators, to increase seed production.

In 1982 Bud and his son, Tim, made a two-row implement that they still use today to interseed grazing lands at a seeding rate of 0.33 to 0.5 pounds per acre mixed with oats in rows 5 feet apart. The homemade implement has sweeps in front of the seeding units that make openings in the sod 1 to 2 inches deep and 6 to 8 inches wide. They have interseeded both crested wheatgrass and native rangeland pastures. Yellow-flowered alfalfa plants compete well with native grasses and fairly to poorly with tame grasses. Once established the yellow-flowered alfalfa spreads and fills in the space between the rows. It competes well with the grasses in the ranch’s sub-arid environment at about 15 inches of precipitation annually. New interseeded stands take four or five years to become fully established.

The spreading of yellow-flowered alfalfa has not only occurred with the Smith’s inter-seeding, it also reseeds itself. Also, antelope, deer, birds and other wildlife feed on the plant and spread seed in their droppings. Bud had one 200-acre pasture full of yellow-flowered alfalfa that he attributes to the plant reseeding itself and wildlife spreading it. In fact the Smith Ranch borders the U.S. Forest Service’s National Grasslands, onto which yellow-flowered alfalfa has spread for several miles.

Uses
Livestock should be excluded from interseedings and not be grazed until the second year. It should be rested for a minimum of a month before regrazing. To maintain the stands it is best not to graze it in the summer and to avoid extensive winter grazing. Grazing land with interseeded yellow-flowered alfalfa tends to attract livestock, reducing impacts on riparian areas and the need for winter supplements.

Dr. Hansen documented that cattle and sheep grazed the yellow-flowered alfalfa in Siberia and noticed that bloat did not appear to be a problem. There is no research that has proven that yellow-flowered alfalfa is bloat-free. However, Bud Smith reports that he has never had a problem with his cattle bloating while rotationally grazing interseeded yellow-flowered alfalfa. Research in Canada suggests that there may be a protein group in it which may decrease the potential for bloat.

Research
South Dakota State University research by Arvid Boe, Patricia Johnson and Kevin Kephart concluded that if the rangeland manager’s objective is to increase forage quality, quantity and animal output regardless of native plant diversity it can be done with successful interseeding of yellow-flowered alfalfa. The SDSU study showed that up to 70 percent of native species may be lost. However, other research has shown that alfalfa’s symbiotic relationship with nitrogen-fixing bacteria improve soil condition and nutrient contents, facilitating the invasion of other exotic or native species.

Agricultural Research Service research conducted by Gerald Schuman has been done on yellow-flowered alfalfa and carbon sequestration. The research was conducted on rangeland on the Smith Ranch that had been interseeded with yellow-flowered alfalfa. The results showed that grass stands thickened, protein increased and 5 tons per acre of organic carbon had been added to the soil.

Most alfalfa tends to lack persistence in areas that average less than 15 inches of rainfall or during extended drought periods. Some work has been done with crossing yellow-flowered alfalfa with established alfalfa lines to create rhizomatous-like varieties with fibrous root systems. Some of the varieties that have been created are Travois, Drylander, Rangelander, Ladak and Spreador that have the ability for new plants to sprout off of mother plants.  FG

If you are interested in learning more about yellow-flowered alfalfa contact Bob Drown, South Dakota Cooperative Extension Service, County Extension Educator – Agronomy, at (605) 244-5622.

Robert W. Drown
Extension Educator
South Dakota State University

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