"Humic substances" is a generic term referencing all natural organic matter found in nature outside the living cell, including humus and humate materials.
Humic substances are found everywhere in nature, arising from the chemical and biological degradation of plant and animals. They are found in soils, sediments, coals, fresh and salt waters, and other natural materials.
Humic substances are the most stable fraction of organic matter in soils and may persist for thousands of years (Stevenson, 1994). Approximately 40-60% of dissolved organic carbon (DOC) in freshwaters & 60-70% of the total soil carbon (C) content occurs in humic materials, representing the largest reservoir of carbon on earth. Their dark coloration is related to quinone structures formed under oxidative soil conditions trapped in the humic hydrophobic condition.
Humus is a brown to black organic substance composed of partially decomposed plant or animal material (i.e. natural organic carbon compounds) that provides soil nutrients and assist in water retention. Generally this material is considered recently degraded organic matter obtained from composted plants or manure material that is applied to soil to enhance micro-flora growth. Low levels of humic acid does exist in humus material.
Humate is a material containing high levels of humic acid and in some cases fulvic acid. Humates was originally humus from decomposed organic materials (i.e. contains repeated carbon units or compounds) that was entrapped by various rock formations millions of years ago. Through time and pressure high levels of humic acid were formed. Humate geologic deposits are found throughout the world and within different mineral deposits. Humates in calcium carbonate (limestone) are considered more desirable for agricultural use than leornardites (e.g. coal) because of heavy metal contaminates.
Genesis of Humic Substances (Humate)
Mumie: Also called shilajit, asphaltum, vegetable asphalt, mineral pitch, is a semihard brownish black to dark, greasy resin that has a distinctive coniferous smell and bitter taste. It’s found in the mountains of Afghanistan, Bhutan, China, Nepal, Pakistan, Tibet and regions of the former USSR. It is often gathered from the steep rock surfaces of mountains during the summer months when temperatures are warmer (Schepetkin et al. 2002). Mumie contains primarily humic and fulvic acids that are of therapeutic value.
Peat: These are humic substances that are formed through the disintegration and humidification of dead marsh plants in conditions of high humidity (Orlov, 1995).
Sapropel: Silted deposits of water reservoirs such as lakes, marshes and sea estuaries contain organic matter. The slow decomposition and humidification of plants and phytozooplankton under anaerobic conditions results in new high-molecular organic compounds such as humic and fulvic acids (Rohling 1994).