Humic acid is a principal component of humic substances, which are the major organic constituents of soil (humus), peat, coal. It is produced by biodegradation of dead organic matter. It is not a single acid; rather, it is a complex mixture of many different acids containing carboxyl and phenolate groups. Humic acids can form complexes with ions that are commonly found in the environment creating humic colloids. Humic and fulvic acids are commonly used as a soil supplement in agriculture.