The Effect of Soil Moisture on the Viscosity of Pastes Prepared from Them

It is known from the literature that the rheological behavior of soils is largely determined by the water content in pastes and soil organic matter, which is the basis of organomineral soil gels. With an increase in soil moisture, gels can swell. As a result, the viscosity of soil pastes should change. The aim of the work was to assess the effect of soil moisture on the viscosity of soil pastes. Arable horizons of soils were used in the work: sod-podzolic, gray forest, leached chernozem and chestnut. During the experiments, soil moisture was changed, but the water content in the pastes for each type of soil remained unchanged. The viscosity of soil pastes was determined by vibrational viscometry, and the size of organomineral particles in pastes was determined by laser diffractometry. For all the studied samples, the existence of two peaks in the viscosity of pastes was found, depending on soil moisture. An explanation of viscosity peaks in pastes is proposed from the perspective of changes in the structure of humic substances in organomineral gels upon reaching critical concentrations: micelles – supramolecular formations – fractal clusters. Apparently, the transition between the structural forms of humic substances under mechanical action on pastes is accompanied by the disintegration of large gel particles and the formation of a more balanced form of existence of humic substances at a given water content.

vibrational viscometry, free water, kinetically bound water, size of organomineral particles in soil pastes, critical concentrations of humic substances