Abstract
The article considers the issues of establishing the root causes of degradation processes on medium kastanozem soils of fallow pastures in the dry-steppe zone of the Kostanay region. It was found that the main reason for the sharp decline in the fertility of medium kastanozem soils that were previously used for arable land was soda-sulphate salinization of the arable and sub-arable horizons. Against the background of small annual and seasonal variability of climatic factors, the intensity of this process most likely depended on the frequency and intensity of deflationary and erosive processes and on the agrotechnical measures taken to improve the water, heat, air regimes and the structural state of the soil. Sulfate salinization covers the entire meter-thick layer of medium kastanozem soil with a gradual increase with depth. The results obtained are a theoretical basis for solving issues of rehabilitation of anthropogenically degraded medium kastanozem soils for their re-involvement in arable land. The conducted studies revealed several issues requiring further research, such as the genesis of soda, the nature and intensity of successional processes, crop yield forecasts and the modern development of fallow landscapes in general.