Abstract <p>A probabilistic assessment of spatial variability of humus content in soils in the river basin system and ravine catchment as its component was carried out using pedotransfer models of humus accumulation. The parameters of relationship between natural and anthropogenic factors, and the natural potential of ordinary chernozem in steppe agrolandscapes using a basin approach were obtained. To reveal the peculiarities of the spatial distribution of humus in soils of the Aidar River basin confined to its upper, middle and lower reaches within the boundaries of the Lugansk People’s Republic (LPR), the statistical analysis of data from two tours of a large-scale survey (1970 and 2011) was performed, the long-term dynamics of humus content was revealed, statistically probabilistic situations were analyzed, a schematic map of modern spatial distribution of humus content was compiled, and the probability of its manifestation in various units of the river basin → ravine catchment system was estimated. The principles of studying natural factors in pedotransfer models of soil formation include consistent mathematical and statistical analysis using GIS technologies and calculations in the following thematic stages: (1)&#xa0;determination of dependencies of humus content and natural potential of ordinary chernozem in steppe agrolandscapes on particle-size distribution, soil profile thickness, terrain elevation a.s.l., and the specific features of territory moistening expressed by the hydrothermal index for different seasons of the year in the northern steppe; (2) formation of pedotransfer models for determining the humus content and natural potential of humus reserves in ordinary chernozem. Nonlinear pedotransfer models allow us to calculate the humus content in soils depending on the entire range of values (minimum, average, maximum) and, taking into account the leading factors, to construct an optimization surface for the relationship between humus content and natural factors.</p>