THE NARURE OF BONDS IN THE FORMATION OF WATER STABILITY OF SOIL AGGREGATES

Abstract

There is an opinion that water stability is provided by hydrophobic bonds between organic soil particles, however, there are works in which the main role in the occurrence of this property is assigned to the presence of hydrophilic organic substances in soils. The aim of the study was to clarify the nature of the bonds (hydrophilic or hydrophobic) that ensure the water stability of soils. The work used samples of sod-podzolic and gray forest soil, as well as leached chernozem. Experiments on the assessment of water stability were carried out by the method of “blades”. It is based on the dissection of linearly arranged aggregates, which were previously moistened in vacuum to values close to saturation. The energy of hydrophobic bonds depends on temperature, so the effect of temperature on the determined value of water stability was studied. Experiments have shown that with an increase in temperature, the water stability of aggregates stored in a wet state from the moment of selection increased, and with a decrease, it fell. This indicates the leading role of hydrophobic bonds in the formation of water stability. For samples dried to an air-dry state, moistened again and kept in a wet state for more than 2 weeks, no temperature dependence of water stability was found. Taking into account that the strength of hydrophobic bonds increases with increasing temperature, and hydrophilic bonds decreases, the data obtained on the immutability of water stability values can be explained if we assume the joint participation of both hydrophobic and hydrophilic bonds in the water stability of soil samples that have passed through the stage of drying to an air-dry state. In fact, these results indicate a strong change in the structural organization of soils during drying.