The term “humus” dates back to the time of the Romans, when it was frequently used to designate the soil as a whole. It was later applied to the organic matter of soils and composts, or to different fractions of this organic matter; as well as, to complexes formed from a variety of natural organic substances. Humus compounds are complex natural organic compounds that are formed in soils from plant residues, by a process of “humification”. Humus materials are complex aggregate of brown to dark colored amorphous substances, which have originated during the decomposition of plant and animal residues by microorganisms, under aerobic and anaerobic conditions, in soils, composts, peat bogs, and water basins. Chemically, humus consists of certain constituents of the original plant material resistant to further decomposition; of substances undergoing decomposition; of complexes resulting from decomposition, either by processes of hydrolysis or by oxidation and reduction; and of various compounds synthesized by microorganisms.
“Humic acid ” is the commercial term often used to refer to the combined humic and fulvic acid content found in these naturally occurring deposits. Humic acid is known to be among the most bio-chemically active materials found in soil.