More than 100 years after an explorer first brought yellow-flowered alfalfa from Siberia to North America, South Dakota State University (SDSU) scientists are exploring one of his century-old ideas – using it to boost the nutrition in semiarid grasslands.
Specifically, SDSU scientists are exploring whether yellow-flowered alfalfa can improve the quality of grazing in pastures of crested wheatgrass. Crested wheatgrass is a non-native, cool-season grass that is nutritious for livestock early in the year, but isn’t as nutritious or palatable as temperatures warm during the summer.
Niels Ebbesen Hansen, a longtime botanist at what is now SDSU, as well as a self-styled “plant explorer” for USDA, introduced yellow-flowered alfalfa to North America. He made eight journeys through Europe and Asia to search for plant material and is famous for finding or developing 350 varieties of fruits, vegetables, trees and other crops.
Hansen collected seed of yellow-flowered alfalfa, Medicago falcate, during his first expedition of 1897-98. He gathered large amounts of the seed in later expeditions of 1906, 1908-09 and 1913. He found yellow-flowered alfalfa adapted as far as northeastern Siberia, where it was able to endure temperatures in the range of -85°F. That suggested to Hansen it would probably thrive on the dry, cold Northern Plains – “my American Siberia,” as Hansen called it.
As early as 1909, in an inventory of plants he had recently brought back from abroad, Hansen suggested yellow-flowered alfalfa could be introduced into native pastures.
More than a century later, SDSU graduate student Chris Misar says a variation of that idea is the point of his research. He and his professors want to know whether interseeding hardy, yellow-flowered alfalfa into crested wheatgrass pastures can allow the alfalfa to get established and bolster the nutrition available to livestock.
Ironically, crested wheatgrass is another plant introduced to North America by Hansen after he saw it at the Valuiki Experiment Station on the Volga River in Russia on a journey for the USDA in 1897-98. But it would be decades before the grass came into wide use.
“Crested wheatgrass wasn't widely utilized until the 1930s and later,” Misar explains. “Crested wheatgrass was planted on many acres of abandoned cropland and degraded rangeland in the west and Great Plains for revegetation purposes. The grass saved a lot of soil from wind erosion due to its ability to grow and protect soil when environmental conditions were poor.”
Funding for SDSU’s yellow-flowered alfalfa research has come through sources such as the South Dakota Agricultural Experiment Station, the Five-State Ruminant Consortium and USFS Grand River National Grassland.
In addition, Misar was awarded a $9,060 grant from the North Central Region Sustainable Agriculture Research and Education Program for the interseeding project as part of NCR-SARE's Grad Student Grant Program. Misar is carrying out his study in plots near Fruitdale and Buffalo in South Dakota, as well as Hettinger, ND, and Newcastle, WY. He’s evaluating seeding date, seeding rate, and sod suppression using herbicide as factors that all can influence the success of interseeding yellow-flowered alfalfa into crested wheatgrass.
Because it’s a legume, yellow-flowered alfalfa is able to fix nitrogen through nodules in its root system, enriching the soil for the crested wheatgrass. It also sequesters some carbon and provides additional habitat. And it’s able to flourish in locations that, in Misar’s study, receive an average 13-15 in. of annual precipitation. However, the challenge is getting alfalfa seedlings successfully established in crested wheatgrass stands.
Lan Xu, SDSU associate professor and one of Misar’s advisers, says because both yellow-flowered alfalfa and crested wheatgrass have been established on the Northern Plains for a century now, there’s no question that both can survive dry, cold conditions. For example, it’s known that Hansen provided seed to Lodgepole, SD, rancher Charles Smith in 1915, and the plant has been established in northwestern South Dakota since then.
“He introduced it nearly 100 years ago and it’s never disappeared,” Misar says. “That’s our motivation to study it – it’s been so persistent. Alfalfa that can survive in Siberia can survive here.”
SDSU range scientists also know, from studying yellow-flowered alfalfa on the Grand River National Grassland, that yellow-flowered alfalfa won’t spread wildly – it prefers fine-textured soils and moist conditions such as the low ground in swales.
“What we have learned is that yellow-flowered alfalfa hasn't become naturalized to the extent sweetclover and leafy spurge have on rangelands. Its distribution, including soil seed bank, is very confined,” Xu says. “Plus, it has incredible value as an agricultural crop.”
Xu notes that naturalized yellow-flowered alfalfa found on the Grand River National Grassland isn't pure Medicago falcate. It probably hybridized with purple alfalfa, Medicago sativa, in nature through pollination.
SDSU researchers also have studied the volume of seed that yellow-flowered alfalfa produces under natural conditions and have explored why its seed doesn’t germinate uniformly and readily. Xu speculates that it’s likely a survival mechanism – germination is staggered to ensure at least some plants will encounter the conditions needed to reach maturity.
“This plant comes from Siberia. It has adapted to that very harsh and unpredictable environment so that it doesn’t all germinate at once,” Xu says.
He says seed-germination research conducted on the yellow-flowered alfalfa by SDSU student Diane Narem found that greater than 99% of yellow-flowered alfalfa seeds from the soil were viable but less than 4% germinated under standard laboratory conditions. The objective of the research was to determine if low germination rate was due to physical or physiological seed dormancy.
“What we have learned from Narem's study is the emergence rate of yellow-flowered alfalfa seeds can be significantly improved by scarification treatments, particularly sandpaper treatments. It indicated the low germination rate is most likely due to physical dormancy,” Xu says.
Yet another study is exploring how various alfalfa populations transplanted to the Antelope Range Research Station near Buffalo, SD, stand up to cattle grazing over multiple growing seasons. Researchers continue to get a better picture of what’s necessary to get yellow-flowered alfalfa established in crested wheatgrass pastures, and how to include the forage in grazing programs.