Use of the color indices of humus soil horizons as indicators of soil evolution in the steppe zone of the Transvolga region under irrigation conditions

摘要

Changes that occurred in the humus parameters and humus horizon color of soils of an experimental production farm in the Saratov oblast during 50 years of irrigation indicate the development of a northern humid version of soil-forming process. Its rate is determined by the confinement of soils to mesoand microrelief elements. The qualitative differences in the character of humification in soils on watersheds and middle and lower slopes are confirmed by statistically reliable differences in the color parameters of soils in the CIE-L*a*b* color system. The lightness (L*) and the yellowness (b*) are the most informative parameters. The lightness is related to the content of humus and probably to its qualitative composition, and the changes in yellowness result from the masking of yellow-colored mineral iron compounds by the newly formed humus. These color indices are reliable criteria for color assessment and can be used for the detection and estimation of changes in the irrigated soils of the steppe regions.