USDA-ARS Central Great Plains Resources Management Research 1 article published in JoVE Environment Improving Infrared Spectroscopy Characterization of Soil Organic Matter with Spectral Subtractions Andrew J. Margenot1, Sanjai J. Parikh2, Francisco J. Calderón3 1Department of Crop Sciences, University of Illinois Urbana-Champaign, 2Department of Land, Air and Water Resources, University of California Davis, 3Central Great Plains Resources Management Research, USDA ARS SOM underlies many soil functions and processes, but its characterization by FTIR spectroscopy is often challenged by mineral interferences. The described method can increase the utility of SOM analysis by FTIR spectroscopy by subtracting mineral interferences in soil spectra using empirically obtained mineral reference spectra.