The Relationship between the Mechanisms of Formation of Erosion Resistance and Soil Water Stability

Abstract

Kuznetsov’s formula relates the parameters of erosion resistance and soil water stability. However, the mechanism of occurrence of these properties is different: water stability is explained by the action of intra-aggregate hydrophobic bonds in organomineral soil gels, and erosion resistance is explained by water stable aggregates and their adhesion to each other. There is a contradiction in the proposed mechanisms of two similar phenomena. The purpose of the work was to clarify the mechanism of erosion resistance of soils and compare it with the mechanism of formation of water stability. The work used samples of humus-accumulative soil horizons: sod-podzolic and leached chernozem. To obtain samples with the same aggregate composition, but differing in erosion resistance, it is proposed to use soil polymer ameliorants (SPMs). The erosion resistance of soils was determined on a hydrolotter and the critical rate of flushing was calculated. The water stability of the soils was assessed by the blade method. The particle size in the solutions was estimated by laser diffractometry. It was found that, on soils treated with SPMs, the results of the tray and blade methods correlate by 99%. The high correlation suggests a common nature of intra- and interaggregate bonds. To test the role of hydrophobic interactions in the formation of aggregates resistant to water, polymers of varying degrees of hydrophobicity were added to aqueous humate solutions in a model experiment: polyethylene glycol (PEG), polyacrylamide (PAA), and polyvinyl alcohol (PVA). In parallel, the water stability of soils treated with PEG, PAA, and PVA was evaluated. Analysis of the results showed that the greatest water stability of the aggregates was noted when the most hydrophobic polymer, polyvinyl alcohol, was added to the soil, which formed the largest particles when interacting with humate in the model experiment. These results confirm the role of hydrophobic interactions in the formation of aggregates and indicate that when selecting polymer structures, their interaction should be taken into account not with clay minerals, but with soil gels, which include clay minerals and humic substances.