Persistent forage has new promise
More than 100 years after an explorer first brought yellow-flowered alfalfa from Siberia to North America, South Dakota State University scientists are exploring how it might improve the quality of grazing in pastures of crested wheatgrass.
Crested wheatgrass is a non-native, cool-season grass that offers livestock good nutrition early in the year, but isn’t as nutritious or palatable as temperatures warm during the summer. 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 receive an average 13 to 15 inches of annual precipitation. However, the challenge is getting alfalfa seedlings successfully established in crested wheatgrass stands.
• SDSU makes progress in yellow-flowered alfalfa research.
• Latest studies focus on improving seed germination.
• Yellow-flowered alfalfa could improve crested wheatgrass pastures.
SDSU graduate student Chris Misar is evaluating seeding date, seeding rate and sod suppression using a herbicide as factors that all can influence the success of interseeding yellow-flowered alfalfa into crested wheatgrass. He is conducting trials near Fruitdale and Buffalo, S.D., Hettinger, N.D., and Newcastle, Wyo.
Associate professor Lan Xu in SDSU’s Department of Biology and Microbiology, one of Misar’s advisers, says because both yellow-flowered alfalfa and crested wheatgrass have been established on the northern Plains for a century, there’s no question that both plants can survive dry, cold conditions. For example, it’s known that N.E. Hansen provided seed to Lodgepole, S.D., 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 it won’t spread wildly — it prefers fine-textured soils and moist conditions such as the low ground in swales.
“Yellow-flowered alfalfa has not become naturalized to the extent sweetclover and leafy spurge have on rangelands. Its distribution, including soil seed bank, is very confined,” Lan Xu says.
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. The simple explanation is probably that it is a survival mechanism — a built-in means of staggering germination so that at least some plants are likely to encounter the conditions that allow them to come to maturity, Lan Xu says.
SDSU research has showed that emergence rate of yellow-flowered alfalfa seeds can be significantly improved by scarification treatments, particularly sandpaper treatments.
Another study is exploring how various alfalfa populations transplanted to the Antelope Range Research Station near Buffalo, S.D., stand up to cattle grazing over multiple growing seasons.
As Misar wraps up his master’s degree study, and as some other SDSU research continues, producers will get a better picture of what is necessary to get yellow-flowered alfalfa established in crested wheatgrass pastures and how to include the forage in their grazing programs.
Nixon is a writer with SDSU AgBio Communications.
This article published in the October, 2010 edition of DAKOTA FARMER.