Physical Indicators and Mechanism of Slitization(on the Example of the Pre Caucasian Merged Chernozem)
Slitization (vertisolization) is a widespread process leading to adverse physical and technological properties of chernozem soils. There is still no single point of view on the genesis of this phenomenon, although it is a priori clear that it is based on physicochemical mechanisms of the interaction of fine particles and soil moisture in swell-shrink cycles. Patterns of the dynamics of the main categories of porosity depending on soil water content have been studied at the quantitative level in genetic horizons of the Pre-Caucasian leached chernozem (Luvic Chernozem (Epiloamic, Katoclayic, Aric, Novic, Bathyvertic) in comparison with a chernozem without vertic features. The physical state of vertic soils is represented by structural diagrams of porosity as a function of the specific volumes of various categories of pores depending on volumetric water content. Their calculation is based on experimental material on the texture porosity of aggregates obtained by saturating individual aggregates with non-polar liquid (toluene) and their humidification with hot water vapor, along with using a fundamental ion-electrostatic model of disjoined pressure. Slitization is characterized by a significant reduction in textural porosity and the prevalence of specific volumes of the external pore space (cracks, inter-aggregate voids) in the overall structure of the porous dispersed system. The most likely reason for slitization is a sharp (two-fold) reduction in the effective width of the double electric layer of the disperse system with increased interaction of particles through stable layers of the liquid phase (compaction effect). In turn, this causes unfavorable technological properties of vertic chernozems, lumpy fragmentation upon drying with the formation of large cracks, which complicates the mechanical processing of such soils and agricultural activities on them.