The aim of the experiment was to assess the impact of unbalanced mineral fertilization on the content of phosphorus and potassium in winter oilseed rape (Brassica napus L.) cv. Kana, winter wheat (Triticum aestivum L.) cv. Sukces and in spring barley (Hordeum vulgare L.) cv. Justina. The experiment was established on brown soil developed from loess with the textural composition of clay dust, which in the Polish soil taxonomy belonged to the agronomic category of heavy soil, the second valuation class and the agricultural usefulness complex of good wheat. Two experimental factors were applied: unbalanced mineral fertilization (five variants), and meteorological conditions (four levels). The doses of individual fertilizer components were adjusted to the nutritional requirements of tested plants. The phosphorus content was determined by the vanadate-molybdate method and potassium was assayed by atomic absorption spectrometry. Before determinations, the plant material was digested in concentrated sulfuric(VI) acid with addition of 30% hydrogen peroxide. Both meteorological conditions and unbalanced mineral fertilization significantly affected the content of phosphorus and potassium in winter forms of oilseed rape and wheat as well as in spring barley. Excluding nitrogen from fertilization is associated with a significantly decrease in the phosphorus content in the straw of tested plants. The absence of potassium in fertilization is associated with a decrease in its content in generative and vegetative organs of test plants. Omission of sulfur in fertilization is associated with a decrease in the potassium content in the straw and increase in the test plants grain.    

24.4.2019