In the conditions of a long stationary experiment conducted in the Saratov region on the Southern Chernozem, it was found that for eight rotations of a six-field grain-pair crop rotation (48 years) in the variant without fertilization, carbon losses from the 0-40 cm layer were the highest. Fertilizers N32P16K7 and N38P13K8 per 1 ha of crop rotation area reduced its losses by 29-32%. When applying N54P17K7, an increase in the migration of organic carbon into the underlying layer of 40-100 cm was noted. The total nitrogen content in the control decreased by 8.7% compared to the initial data. The introduction of N15P13K8 and N38P13K8 per 1 ha of crop rotation area contributed to the preservation of nitrogen compounds in the humus layer of the soil. The content of total phosphorus in both non-fertilized and fertilized soil has changed slightly over 48 years of research. Systematic application of fertilizers led to an increase in the fraction of calcium phosphates.