A field experiment was carried out on the lessive, very acid soil. The scheme of the experiment consisted of five fertilization treatments: control (without fertilization), NPK, NPK+MgSO4 7H2O, NPK+MgO+CaO, NPK+farmyard manure (FYM). Mineral fertilizers were
applied according to the recommendation worked out in “NAW-2” program. Winter rape, winter wheat and oats were used as the test plants. The soil samples were collected after plant harvest from 0–20 cm, 20–40 cm, 40–60 cm depths. Available phosphorus according to the Egner-Riehm method, fractions of mineral phosphorus, according to the Chang and Jackson method in the modification of Askinazi, Ginzburg and Lebiediewa (easily soluble P, P-Al, P-Fe P-Ca) were determined in the samples. Lime, NPK and magnesium application had a beneficial effect on the available phosphorus content under conditions of very acid soil. The applied fertilizers influenced the content of mineral phosphorus fractions. Fertilization with NPK, FYM increased the amount of aluminium and iron phosphates as well as the sum of mineral phosphorus fractions; NPK+MgO+CaO application increased the content of all mineral phosphates and NPK+MgSO4 7H2O fertilization decreased the content of all phosphorus fractions, with the exception of the easily soluble phosphates.