The article presents the analysis of the results of a long-term experiment on studying the effectiveness of the combination of the doses of lime and mineral fertilizers on sod-podzolic sandy loam soil in crop rotation in the Leningrad region. Research experiments are carried out in the six-field crop rotation. The data obtained in the course of long-term stationary field experiments are more reliable and accurate compared to the results of model experiments. The liming and long-term uses of mineral fertilizers affect the crop nutrition pattern and the migration capacity of substances in soils. The application of moderate doses of mineral fertilizers during soil liming increases the number of bacterial microflora. Liming significantly increases the nitrification capacity of the soil. Liming of strongly acidic sod-podzolic soils increases the amount of phosphorus and fertilizers the crops take from soil. Calcium, which is a part of phosphorus fertilizers, is essential for acid-sensitive crops. The optimal reaction level for crop development is not constant. In case of a good crops supply with nutrients, the optimal reaction level shifts to a more assiduous area. As a result, the knowledge of the process patterns occurring in the soil under the influence of anthropogenic agricultural activity was obtained. The data obtained are the key to control the soil evolution during its agricultural use.

In a model experiment, a study was carried out on potassium leaching from the soil. Soil samples were taken from a protective strip of long-term experiment (established in 1981). Various fertilizers and their mixtures were introduced. The effect of organic matter on the capacity formation of the cationic soil exchange was considered. Significant differences were noted in the potassium migration during various fertilizers application. A significant role is played by liming of acidic soils. Potassium ions displace calcium ions more easily calcium ions from the soil absorption complex than aluminum. Therefore, when liming, leaching of potassium may be reduced. With the introduction of peat and peat-based fertilizers, the cation exchange capacity of the soil increased significantly. The leaching of potassium did not increase. Introduction of cattle manure without heat treatment significantly increased the migration of potassium in the soil and its leaching to the lower lying horizons. In general, the migration and leaching of substances in arable soil rely upon a number of factors and their combinations: natural and climatic factors, physical and chemical properties of the soil, the intensity of agricultural use of arable land, the type and composition of fertilizers, and the mineralogical composition of the soil. When growing plants on calcareous, fertilized with potash fertilizers soils, the loss of potassium does not exceed its leaching from non-fertilized soils.