Soil organic matter (SOM) holds a prominent place among the many indicators that are studied in relation to soil function. Different
viewpoints are reflected in characterizing SOM, depending on the study procedures used, or the focus of the researchers. There are
many possibilities for the isolation and fractionation of SOM and this has led to a plurality of interpretations and conclusions. Transformations
to organic materials that lead to the more recalcitrant components of SOM are outlined, and the associations which these materials
can have in the soil environment, and aspects of their compositions are referred to. A review is given of the organic matter pools in
soils, of their functions, and of the controls which they have in soil systems. A succinct review is given of physical fractionation procedures
for SOM. This approach is highly relevant, though rarely used in modern studies of SOM. The merits and demerits of wet oxidation
procedures, relative to dry combustion for determining soil organic carbon contents are discussed, and reference is made to the emerging
chemometric techniques based on the use of Near (NIR) and Mid (MIR) infrared spectroscopy.
Keywords: Carbon measurement, Fractionation, Soil carbon, Soil function, Soil organic fraction, Soil quality indicator.
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