Clover Improves Soil Quality, Feeds Biofuels Crop

by Christie Delfanian (South Dakota State University/Phys.Org) A four-leaf clover might bring good luck, but a stand of Kura clover can produce healthier soil—in the long run, according to a South Dakota State University study.

Planting Kura clover, a pasture legume, with prairie cordgrass can improve microbial activity in the soil, thus reducing the amount of fertilizer needed to produce the potential biofuels crop, explained Associate Professor Sandeep Kumar of the Department of Agronomy, Horticulture and Plant Science. That news is good for both the producer and the environment.

"We are seeing an increase in soil health in stands where there is little diversity—only two species," said Professor Vance Owens, director of the North Central Regional Sun Grant Center. But it takes time to see those benefits.

Ten years ago, Owens and Associate Professor Senthil Subramanian planted prairie cordgrass and Kura clover at the South Dakota Agricultural Experiment Station Felt Farm, north of campus, as part of a multi-institutional North Central Regional Sun Grant Center project. The SDSU team collaborated with researchers from the University of Minnesota, University of Wisconsin-Madison and University of Illinois at Urbana-Champaign.

"We wanted to see what kind of nitrogen replacement value Kura clover could provide," Owens explained. "It took until the fourth year before we saw any direct benefit in terms of yield in the prairie cordgrass plots mixed with Kura clover, but by then, the nitrogen benefit from the Kura clover ranged from 20 to 80 pounds per acre across the four locations."

When Kumar took over the ongoing project in 2013, he expanded the research to assess greenhouse gas emissions and, most recently, to evaluate soil health parameters, such as organic matter and microbial activity. That led to the discovery of further benefits from Kura clover.

As a perennial legume, Kura clover enriches the ecosystem by transferring nitrogen from the atmosphere into the soil through bacterial interactions with the plant's root system (N-Fixation). The winter-hardy clover works well in combination with native grasses. "It's well suited to the marginal lands utilized for perennial biofuels crops," Owens said.

Kumar and postdoctoral research associate Udayakumar Sekaran compared soil samples from plots of monoculture prairie cordgrass on which varying levels of nitrogen fertilizer were applied with those in which prairie cordgrass was grown in a mixture with Kura clover. Because one of the fertilizer applications rates was zero, unfertilized prairie cordgrass can be considered control plots, Sekaran pointed out. Switchgrass grown alone was also used as a control for the comparison of two perennial grasses. READ MORE