Environmental control and agricultural management problems involve the simultaneous transport of water and mixed salts solutions with ions that interact with the soil matrix. The soil solution–soil matrix interactions include phenomena such as cation exchange, anion exclusion, precipitation and dissolution, swelling and reorganization of the soil colloid structures, and, concurrently, rearrangement of the soil pore-size distribution; the latter can affect the soil hydraulic conductivity and retentivity. These interactions, therefore, may considerably affect water flow and solute transport.

The magnitude of the soil solution–soil matrix interactions depends to a large extent upon the types and amounts of inorganic and organic soil colloids. Among soil mineral colloids, the most reactive constituents are the smectite minerals (eg, montmorillonite, beidellite, monronite), characterized by dioctahedral structure. The presence of these …