Morphometric Parameters of Typical Chernozem Aggregates and Their Changes under the Influence of Model Shallow-Water Flows

Abstract

Chernozems are the most fertile soils in Russia. Most of the territory of Kursk oblast is covered with chernozems, half of the territory is plowed, and approximately a fifth of the arable lands are eroded. Thus, studies of various aspects of erosion processes affecting the chernozems of Kursk oblast become relevant and important. The aim of the work is to evaluate the influence of shallow flows on the morphometric characteristics of typical chernozem aggregates of varying degrees of erosion. A series of model erosion experiments have been carried out with capillary-moistened bulk samples of the upper 10-cm layer of the humus horizon of typical plowed chernozems of Kursk oblast. The control variant is a comparable sample of chernozem from a typical site, Mown Steppe of Alekhin Central Chernozem Natural Biosphere Reserve. The morphometric parameters of soil aggregates carried by model flows with minimum, average, and maximum rates (0.3, 0.41‒0.45, and 0.54‒0.58 m/s, respectively) have been determined. It has been shown that smaller aggregates have greater roundness, isometry, and a lower surface evenness. Larger aggregates, on the contrary, are less rounded and isometric and are rougher. An exposure of a bulk soil sample to a model shallow-water flow has revealed an inverse relationship between changes in the degree of roundness and the unevenness coefficient of the surface of aggregates. The changes in the form factor and the unevenness coefficient of the surface of aggregates are influenced by both the degree of soil erosion and the flow rate; moreover, these factors mutually enhance the influence of each other. The degree of isometry of aggregates (roundness) is influenced mainly by the degree of soil erosion, but its influence increases by the flow rate factor. The flow rate has different effect on the morphometric parameters of aggregates: a low flow rate has rounding effect, while a high flow rate has a destructive effect. Continuation of such research will expand our understanding of the mechanisms and patterns of formation of eroded soils.