V.V. Dokuchaev Soil Science Institute

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Influence of soil drying on the formation of structural elements in gray forest soils

A. Ya. Voronin

V.V. Dokuchaev Soil Science Institute, 109117 Moscow, Pyzhevskii 7, bld. 2

Peculiar features for the formation of structural elements (clasters) and regularities in their growth have been identified by precipitating the clay fractions extracted from samples of gray forest soils in water suspensions with the view of determining the mechanism responsible for the formation of the soil microstructure under the influence of temporary wetting-drying processes. Under use were suspensions of soil samples (<1 mkm) prepared by traditional methods for the particle-size distribution and microaggregate analyses and preliminary dried (1-2 times). One suspension drop taken by a pipette from the middle part of the test-tube was placed on the laboratory glass of 1x1 cm size. After the water evaporation (48 hours) this procedure was repeated once more and 14 samples were prepared including 7 samples with the clay precipitation from one suspension drop and 7 samples from two suspension drops. Then the raster electronic microscope REMJEOL 6060A was used for scanning of these preparations. The mathematical processing permitted to identify tend towards increasing the accumulation of fine-sized particles, its quantity and decreasing the distance between the formed clasters in the course of their precipitation. When developing clasters of the second order (cyclic precipitation) it seemed possible to establish that the distribution density of structural elements is sharply increased and newly formed clasters can lead to irreversible changes in the soil microstructure and the aggregate destruction. Only the humus promotes weakening these processes. In samples of parent materials such changes in the size of claster doesn’t occur under identical conditions.

Keywords: claster, particle-size distribution, microaggregate analysis, fractal analysis, dispersion coefficient.

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