|Mitchell, Robert - Rob|
Submitted to: Global Change Biology Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2013
Publication Date: 2/3/2015
Publication URL: http://handle.nal.usda.gov/10113/62133
Citation: Stewart, C.E., Follett, R.F., Pruessner, E.G., Varvel, G.E., Vogel, K.P., Mitchell, R. 2015. Nitrogen and harvest treatment effects on soil properties under non-irrigated switchgrass and maize after 9 years: implications for soil quality . Global Change Biology Bioenergy. 7,288-301. DOI:10.1111/gcbb.12142.
Technical Abstract: Switchgrass (Panicum virgatum L.) is a perennial, cellulosic biofuel feedstock capable of growing under a wide variety of climatic conditions on land marginally suited to cultivated crops. Despite greater switchgrass root production compared to maize, researchers observed similar soil C sequestration rates after 9 years in a non-irrigated study evaluating N fertilizer and harvest management treatments on switchgrass (harvested at Aug. and Oct.) and no-till maize (with and without stover removal) (Follett et al. 2012). To quantify the form of switchgrass (Cave-in-Rock) and maize-derived organic C we sampled these plots to a depth of 150 cm in 2007 and fractioned the soils into labile (POM) or stable (silt+clay) soil fractions, and natural abundance 13C. We then assessed plant biomarkers through the profile using cupric oxide extraction and pyrolysis-GC/MS. Through the entire 0-150 cm profile, switchgrass had greater root biomass and a greater root C:N ratio than maize. Both the POM and silt+clay fractions in the 0-30 cm depth incorporated the higher switchgrass C:N ratio, suggesting that root-derived contribution to SOM under switchgrass may derive directly from lignin rather than root exudates. Lignin biomarkers under maize were more decomposed than under switchgrass, reflecting greater root turnover. These results illustrate complex, plant-specific interactions of nitrogen fertilization and harvest timing on root biomass and soil fraction C.