Humic acid. Humic acids are a principal component of humic substances, which are the major organic constituents of soil (humus), peat and coal. It is also a major organic constituent of many upland streams, dystrophic lakes, and ocean water. It is produced by biodegradation of dead organic matter. Post navigation Previous PostPrevious Is Humic Acid Fertilizer?Next PostNext How Humic Acid Improve Soil?