Paper reports on soil nutrients in biofuel production systems in the southeast United States

A recent paper summarizes soil carbon and nitrogen dynamics from four independent but similar ongoing studies in the southeast United States in which switchgrass (Panicum virgatum L.) was grown in monoculture or alley cropping systems. The authors also compare results from the four studies with those for conventionally managed loblolly pine or agricultural systems.

Switchgrass is a native, perennial C4 grass that has been identified by the U.S. Department of Energy as a model dedicated energy crop species.

The paper, which appears in Forest Ecology and Management, was authored by Michael A. Blazier, Louisiana State University Agricultural Center; Terry R. Clason, USDA Natural Resource Conservation Service, Hal O. Liechty, University of Arkansas Monticello, Zakiya H. Leggett, Weyerhaeuser NR Company, Eric B. Sucre, Weyerhaeuser NR Company. Scott D. Roberts and Kurt Krapfl, Mississippi State University, and Eric D. Vance, NCASI.

The authors conclude that “over the range of site conditions and management practices observed in this research, soil parameters in alley cropping systems of loblolly pine and switchgrass were similar to those observed in switchgrass monoculture or conventional conditions found in juvenile loblolly pine plantations.”

The abstract for the paper follows.

“Switchgrass has favorable characteristics as a biofuel feedstock, and it may be feasibly grown on sites currently forested or retired from agricultural production. It is ecologically important to understand the impacts of establishing and managing switchgrass on site nutrient cycling. Four studies conducted in the southeast United States tested switchgrass as a bioenergy crop grown in monoculture, in alley cropping systems, and as an alternative to conventional agricultural rotations. Each trial included comparisons of switchgrass with the prevailing land uses. In each trial, nitrogen mineralization (Nmin), nitrification (Nnit), microbial biomass carbon (Cmic), microbial activity, and labile carbon were measured because of their sensitivity to management practices that alter soil nutrient cycling. In all studies of loblolly pine and switchgrass, switchgrass was apparently the dominant substrate source for Cmic, and Nmin increased when juvenile loblolly pine was isolated with herbicide as the sole vegetation. However, Cmic and Nmin of loblolly pine-switchgrass alley cropping systems were similar to those observed in conventional juvenile loblolly pine plantation conditions. In a trial of converting former agricultural fields into switchgrass or cottonwood biofuel plantations, this conversion reduced Nnit, and therefore the potential for nitrogen losses compared with those for a soybean-sorghum rotation typical for such sites.”

  

Reference 

Blazier, M.A., T.R. Clason, H.O. Liechty, Z.H. Leggett, E.B. Sucre, S.D. Roberts, K. Krapfl, and E.D. Vance. 2015. Nitrogen and carbon of switchgrass, loblolly pine, and cottonwood biofuel production systems in the southeast United States. Forest Science 61(3):522–534. http://dx.doi.org/10.5849/forsci.14-016