Degraded soils that are economically marginal and environmentally vulnerable are unsustainable with the current cropping systems. To attain sustainable production on marginal soils, new cropping systems that minimize long-term economic and environmental risks are needed to restore soil health and sustainability of these soils.
Dr. Newell Kitchen, Soil Scientist of USDA-ARS, Columbia, Missouri, teamed up with coworkers at USDA-ARS: Drs. Ken Sudduth, Bob Kremer, Matt Yost, and Kristen Veum; Drs. Allen Thompson, Stephen Anderson, Ray Massey, and Brenton Myers (now with DuPont Pioneer) of University of Missouri; and Dr. Emily Heaton from Iowa State University to determine soil health remediation and production potential when growing miscanthus and switchgrass on marginal claypan soil.
Kitchen’s research team utilized the already-established Soil Productivity Assessment for Renewable Energy and Conservation (SPARC) plots near Columbia, MO (See photo) for this project.
Kitchen’s group found that miscanthus rhizomes planted on eroded soils performed well. On eroded claypan soils, only about 30% of the time required N fertilizer to maximize Miscanthus yield. Relative leaf chlorophyll concentration was found as an accurate indicator of fertilization need.
Switchgrass had greater water use efficiency (WUE), about 50% greater N recovery efficiency and about 50% less run-off compared to corn. In addition, soil hydraulic properties of the marginal claypan soils improved when switchgrass was grown (3% lower bulk density, 73% greater hydraulic conductivity, and 53% larger proportion of soil macro pores) compared to corn-soybean cropping system.
Kitchen’s group also determined that switchgrass planted on degraded soil with shallow topsoil had greater quasi-steady infiltration rate and field saturated hydraulic conductivity than row-crop management. “When our results were applied to 24-hour USDA NRCS Type II storm model, switchgrass enhanced estimated infiltration, reduced estimated run-off and decreased estimated water ponding time when compared to row crop management,” Kitchen said.
In terms of the production relative to the topsoil thickness of claypan soil (depth-to-claypan or DTC), net return was greater for corn and soybean over most DTC, while switchgrass was only able to compete on very shallow DTC (<5 cm). Conversely, ethanol production from switchgrass increased with greater DTC for drier than average years and with N fertilization.
“These findings will help farmers know where to grow perennial bioenergy crops instead of grain crops, especially on eroded claypan soils, in order to improve production and minimize negative environmental effects associated with perennial plant bioenergy production”, Kitchen said.
Funding of this project was provided by the U.S. Department of Agriculture-National Institute of Food and Agriculture (USDA-NIFA) through the South Central Sun Grant Program.