ABSTRACT
Due to the possibility of using C sequestration in soil as a means to remove CO2 from the atmosphere, and with the potential for payments for such endeavors, there is an increased interest in determining the changes in amounts of C present in soil. Due to differences in the lability of various forms of soil C, there is also interest in determining differences in the composition of the C present. At present, the “gold standard” for determination of total, organic, and inorganic C in soils is combustion, which can also be used to simultaneously determine total N and S depending on the particular instrument and instrument configuration used (Bremner, 1996). However, combustion analysis requires two runs to separate the organic and inorganic C (in the form of carbonates) and cannot determine nonorganic, noncarbonate C, noninorganic C (charcoal, etc.) as different from organic C. It also cannot determine labile as opposed to nonlabile organic C unless extractions are performed and the C content of the extracts determined. Other methods available for determination of soil C include laser-induced breakdown spectroscopy (LIBS) (Ebinger et al., 2003), ground penetrating radar (GPR) for determining root mass (NRCS, 2004), neutron activation spectroscopy (NAS) (Glascock, 2004), and near-(NIRS) and mid-infrared-(MIDIR) reflectance spectroscopy, also called DRIFTS for diffuse reflectance MIDIR Fourier transform spectroscopy (Nguyen et al., 1991; Reeves,
1996; Janik et al., 1998; Reeves and McCarty, 2001; Reeves et al., 1999, 2001).
