Glossary

Humic Acid Complex

The humic acid complex (also called clay-humus complex) in soil science refers to aggregate formation of organic fragments (e.g. humic substances) and inorganic particles (e.g. clay minerals). It is accomplished either by hydrogen bonding or the incorporation of metallic cations. Clay minerals and humic substances are both soil colloids. Humic substances can combine individual soil particles into a crumb structure and thus stabilize the soil structure. Such aggregate structures develop in humic top soils when clay colloids connect with humic substances by means of calcium bonding.