Discussion problems of humus nature
Authors: Tsapko Yu. L. 
Published: February 2020

The article is based on a generalization of the author's prior research and review of scientific sources, discussion questions about the nature of humus are put and in particular the latest structural views on the structure of humus are given. Is emphasized that despite the long experience of studying soil humus question its structural buildings has not been studied. Nowadays the scientific community there are a number of different and often antagonistic hypotheses on which the structure of humus is significantly different. Based on the features of genetic connection between fulvic and humic acids, which serve as precursors of the second, examined in detail the mechanism of formation humic acid as a result Connection by transverse by chemical bonds fulvic acid cyclic compounds through reactionary groups. The model of clathrate structure of humus is proposed, which shows that it has huge molecular weight inherent megamolecules or supramolecules. Mega molecules that are linked by hydrophobic powers and mineral soil matrix serve as the next level of organization (ordering) of humus. The last one causes extreme stability of clathrate structures of humus, and their ability to provide stable soils, a kind of buffering, certain biochemical background, color and so on. It is noted that the high stability of clathrates structure of humic acids provided by the presence in their inner part of a significant number of structured water. The high stability of clathrates is also explained by the fact that they necessarily contain such an integral part of humus as humic, which is closely associated with the mineral soil matrix. This fact allows to present the clathrate structures in a general model of humus. The proposed model crown clathrate buildings of humic acids allows the display of their interaction with cations, which is the basis for assessing changes of acid-base balance of soils. Because of the inherent humic acid clathrate structure becomes clear very high resistance to water the last as well as to acid hydrolysis. Due to the high biological activity of chernozems and high content of clay minerals, and thus high content of aluminum, is not observed the increasing of acidity and mineralization of humus. In our view, the first one is because of the fact that mobile aluminum and its compounds are the part of the inner clathrates structure and lose their reactivity and are not able to acidification of the soil environment; and the second one is because of the clathrates resistance of humus. In the latter suggests the following – distinction (single) crown compounds are rather easily destroyed by microorganisms, that is due to the high microbiological activity of soils, for example in the brown soils. However, in chernozems, in similar circumstances, there is an extremely high humus resistance as to different types of hydrolysis and mineralization also. In the sod-podzolic soils and the brown soils the processes of compound crowns of fulvic acids in a complex of humic acid clathrates are slowed down. As a result, the ratio of humic acid and fulvic acid decreases, and as a rule, the soil acidity increases. The opinions on the structural organization of humus presented in article are only part of the problems. Their solving is dictated by the need for the development of modern science about soils. The other opinions in the context of the article, and in many other fields of Soil Science are extremely interesting.