Fourier-transform infrared spectroscopy for soil organic matter analysis

The study of soil organic matter (SOM) can benefit from the use of Fourier-transform infrared spectroscopy, an analytical method that complements traditional fractionation and extraction methods. This review provides guidance on the use of diffuse reflectance infrared Fourier transform (DRIFT) in the mid-infrared region (MIR: 4000–400 cm⁻¹). Two distinct applications of DRIFT spectroscopy are reviewed: soil organic matter (1) characterization and (2) quantification. Characterization of SOM involves the qualitative to semi-quantitative measurement of functional groups that constitute organic matter, and quantification employs chemometrics to predict fractions of SOM. Guidance on decision-making in how methods are conducted based on sample type and research question, and on interpretation of results are provided.