CHEMICAL PROPERTIES OF SOIL
Soil is a highly dynamic system which supports complex chemical reactions. In this heterogeneous systems, the soil solution acts as the medium for complex chemical reactionr. Soil colloidal components (clay and humus) bind the exchange cations on the surfaces. Cation exchange is one of the most important soil reactions. Colloidal soil particles such as humus and clay usually bear electronegative charge. The charge may be the result of the adsorption of an excess of anions or the result of an imbalance in the atomic charges in the crystal lattice of clay rnicelle. To balance the negative charges, the particles tend to adsorb cations on their surface (see Figure shown below). The balancing ions are called exchangeable cations and are in kinetic equilibrium with the soil solution.