KNOXVILLE Tenn. — Can native grasslands enhance soil biodiversity and contribute to producer profitability?

That’s what researchers are hoping to learn in a new study at the University of Tennessee Institute of Agriculture.

The question is, how can these grasses produce such large amounts of biomass with such little fertilizer input? “We have been looking at native grass forages, things like switchgrass, big bluestem, Indian grass, Eastern gamma grass,” said Patrick Keyser, director of the UT Center for Native Grasslands Management. “What we’ve learned in our research is that they seem to be good summer forages. One of the intriguing things about them is they seem to be able to do well with little fertility.”

He is investigating how these grasses produce large amounts of biomass with little fertilizer input. One possible explanation is that the root mass the grasses produce on a regular basis eventually die, turn over, decompose and turn into nutrients because they have such a deep root system and produce so much below- ground biomass.

Still, other questions come up, Keyser said, including: Is there a relationship between native grasses and soil microbes? The researchers will look under the surface at both hayfields and grazing situations.

“What is going on down there in that black box we call the soil that allows these grasses to be so thrifty?” Keyser said. “This study is an effort of pulling together a big team of scientists to begin to unravel that mystery.” 

 

The scientists hypothesize that fertility and cover crop management practices, such as planting legumes or other winter cover crops, exert a strong influence over components of soil biodiversity, he said. As the cover crops degrade, researchers believe they provide an organic fertilizer source.

“If we increase the inputs of fertilizer, as a farmer that costs us more money; we get the benefit, but it costs us more,” Keyser explained. “If we’re not careful where we apply that extra fertilizer, it could wind up in a creek or pond where it may be causing harm.

“There is such a thing as too much fertilizer, economically and ecologically. One of the things we want to figure out is, when I add inorganic fertilizers to theses native grass stands, how does it impact what is going on inside that black box?”

UT is not the only university interested in native grasses and soil biodiversity. Steve Culman, Ohio State University assistant professor of soil fertility, has done several research projects involving the native prairies in Kansas on soils that had never been tilled.

“We went down to the first 3 feet of the soil,” he said. “We found in the context of greater biodiversity bacteria and fungi and nematodes that we were looking at, there were more complex communities of all those organisms in the native prairies, versus the adjacent annual crops.”

These studies allowed researchers to understand a little more about how agricultural systems function and the type of life that they support, and what implications that might have for the farming community.

“I think it is clear that when you have continuous cover, whether from perennial grasses or from annual crops with cover crops, you typically see scenarios with greater biodiversity, greater atrophic complexity, more atrophic orders in that soil food web,” Culman said. “When we have continuous cover of the soil and roots, then you get greater diversity in general.”