Humic acid is a partially decomposed aromatic, organic matter that originates from terrestrial vegetation. It is made up of dark colored amorphous materials and is the end-product of the action of bacteria and certain enzymes. Most of the humic acid has a large fraction of carboxylic functional group which enables the humic acid molecule to chelate with positively charged multivalent ions (Mg++, Fe++ etc). The action of chelation helps plants to absorb the nutrients effectively. This function is one of the most important roles of humic acid. Humic acid also contains the phenolic functional group.;Humic acids are derived from peptide, lipid and carbohydrate precursors. Peat, lignite coal, leonardite,decomposing driftwood and fish excreta are rich in humic acids. Leonardite is a highly oxidized form of organic matter and is technically known as a low rank coal which is between peat and sub-bituminous coal. Most of the humic acid found in rivers, lakes and even oceans has flowed from land over long periods of time. In the aquatic media, humic acid molecules develop unique characteristics.Humic acid can be broken down into two groups, based on the size and polarity of the individual components. The smaller, more polar fraction is called fulvic acid and the larger, non-polar fraction is the humic acid. The acids are soluble in sodium hydroxide.Humic acids are soluble in alkaline solutions. But on acidification of the alkaline extracts, they precipitate (Fulvic acid, on the other hand, remains soluble on acidification of the extract). Their molecular weight is in the range of tens of thousands to a million. They are believed to be polymerization products of fulvic acids and their decay products.The three main components of humus are humin, humic acid and fulvic acid.

• A brown, polymeric constituent of soils, lignite, and peat; it contains the brownishblack pigment melanin. It is soluble in bases, but insoluble in mineral acids and alcohols. It is not a well-defined compound but a mixture of polymers containing aromatic

3.3 Usage