ABSTRACT
The ability of soil organic matter to adsorb both cations and anions from the soil solution is one of the most important benefits derived from its presence in soil. The release of these ions to the plant root occurs by ion replacement. Cation exchange capacity is of great importance, involving most of the cations in the soil solution. However, very few anions are adsorbed by soil organic matter with sufficient strength to make this a major factor in soil productivity. Charges on soil organic matter arise from the ionization of various functional groups including carboxyl, phenolic hydroxyl, enolic hydroxyl, and possibly other groups. Spectroscopic methods provide valuable information concerning the chemical and physical properties of soil organic matter. Fractionation of soil organic matter according to solubility may be accomplished by sequential extraction and differential precipitation. The final major property of soil organic matter which can be utilized as a basis for fractionation is its adsorption potential.
