Changes in soil properties at different levels of soil structural arrangement under the impact of irrigation

Processes taking place at different levels of the soil structural arrangement in irrigated and rainfed soils of the Lower Volga region are analyzed. Interactions between these processes and the dependence of their rates on the duration of irrigation are discussed. It is shown that irrigation-induced changes are more pronounced and proceed faster in soils of poorly drained landscapes in comparison with well-drained landscapes. Interaction of the processes taking place at different hierarchical levels of soil arrangement is observed. At the ionic-molecular level, migration and transformation of the composition of soil humus and soluble salts and various exchange reactions take place; at the level of elementary soil particles, the processes of disintegration, peptization, transformation, and the destruction of minerals; at the aggregate level, changes in the water stability of soil aggregates and the degree of soil micro- and macroaggregation; at the level of particular morphological elements, horizons, and pedons, reorganization of soil material (changes in the thickness and bulk density of soil horizons, synthesis and destruction of various neoformations, etc.); finally, at the level of the soil cover pattern, irrigation leads to a higher complexity of the soil cover; the degree of contrast in the soil cover pattern increases, and the soil development at different sites proceeds with different velocities.