The fertility of soils in macro and microelements, ballast ions – sodium and chlorides, pH and EC on the stand of the Rogalin Oaks – Rus, Czech and Lech was investigated. It was shown that the reasons of the Rogalin Oaks dying should include the degradation of soils which was apparent in the insufficient content of macro and microelements. Among the macroelements – in the whole soil profile of 0-100 cm – insufficient contents of nitrogen, phosphorus (apart from the 0-20 cm layer), potassium, magnesium an sulfur was found. Among microelements, insufficient content of iron – in the whole profile, manganese and copper – below the depth of 20 cm, and zinc below 20 cm on the stand of Czech, 40 cm – for Lech and 60 cm for Rus were observed. In the soils under the oaks a high content of calcium was determined, which increased the soil pH to an unfavourable level. On the stand of Rus pH in the whole profile was 6.33-6.62, on that of Czech – 6.48-6.63, and Lech – 6.15-6.39 in the layers of 0-60 cm, and 5.72-5.58 – below 60 cm, while the favourable level is 5.5-6. A high level of calcium with a deficit of magnesium caused an incorrect Ca:Mg ratio, which was 35.4 on the stand of Rus, 43.9 – of Czech, and 20.6 – of Lech, when the optimum is 6-9. The unfavourable state of fertility was deteriorated by the accumulation of chlorides which exceeded 3 mg Cl·100-1 g of soil d.m. Fertilization of soil under the oaks for a period of 3 years, applying the deficient macro and microelements, improved the growth of the Rogalin Oaks.