Properties and formation of humic substances
The humic substances and their formation have been investigated in the paper. The experimental research in order to determine their properties is conducted. Their formation occurs in several ways. The first theory (the theory of lignin) says that the lignin is not yet fully utilized by microorganisms; it becomes part of the residue of soil humus. The second and the third theories (the polyphenol theory) state that phenolic aldehydes and acids released from lignin during microbial decay undergo fermentation change to quinones, which in their turn polymerize in the presence or absence of amino compounds to form humic macromolecules. The fourth theory (Sugar-amine condensation) is about reducing sugars and amino acids formed as by-products of microbial metabolism are influenced by nonenzymatic polymerization to form brown nitrogenous polymers of the type produced during dehydration of certain food at moderate temperatures. On the basis of properties of humic substances and conducted experimental studies some dependences of concentration of humates have been got depending on the time of extraction, with different concentrations of alkali identified.