Applications of Mid-Infrared Spectroscopy to the Determinations of Soil Amino Sugars, POM-C and N and Water Soluble Carbon in Some Canadian Agricultural Soils.

The objective of this study was to determine if models developed from mid infrared spectroscopy could be used to estimate soil amino sugars (ASs), carbon and nitrogen contents in bulk soil and in particulate organic matter (POM) fractions, and water soluble organic carbon (WSC) in some agricultural soils from west to east. Two hundred eighty six soil samples collected from various sites, including British Columbia, Alberta, Ontario and Québec were used in this study. The contents of organic C and total N in bulk soils and POM fractions were determined using dry combustion method, and the contents of WSC were also analyzed using a TOC analyzer. The bulk soil samples, POM fraction samples, and water extract solution for TOC analysis were scanned from 4000 to 500 cm-1 for mid-infrared (MIR) spectra. Partial least squares regression (PLSr) analysis and the “leave one out” cross-validation procedure were used for the model development. The models were developed using the spectra collected from bulk soil for organic C and total N, the spectra from bulk soils and POM fraction for POM-C and POM-N, and the spectra from bulk soil and water extract solution for AS and WSC determinations. Results indicate that MIR-PLSr model can be used as an alternative method for estimating organic C and total N in bulk soils and POM fractions and for estimating WSC from the spectra collected from water extract solution, however, the estimates of ASs are poor no matter from the MIR spectra from bulk soil or from water extract solution.