Soil colloids

Soil colloids are the most active portion of the soil and largely determine the physical and chemical properties of soil. Inorganic colloids (clay minerals, hydrous oxides) usually make up bulk of soil colloids. Colloids are particles less than 0.001 mm in size and the clay fraction includes particles less than 0.002 mm in size. Therefore, all clay minerals are not totally considered as colloidal. The organic colloids include highly decomposed organic matter generally called humus. Organic colloids are more reactive chemically and they generally have a greater influence on soil properties per unit weight than the inorganic colloids. Humus is amorphous and its chemical and physical characteristics are not well defined. Clay minerals are usually crystalline and usually have a characteristic chemical and physical configuration. Both inorganic and organic colloids are intimately mixed with other soil solids. Thus, the bulk of the soil solids are essentially inert and the majority of the soil's physical and chemical character is a result which indicates the presents of colloids.

Soil colloids