Variations in concentrations of 24 elements in soils with loam and sandy loam texture and in Triticum aestivum wheat seedlings grown in the soils under greenhouse conditions were studied. Initial soils differed significantly in concentrations of 20 elements. Elemental composition of wheat seedlings depended on the soil where the plants were grown. An application of ISPOLIN (fertilizer enriched with potassium) resulted in variations in soil pH, plant biomass, and concentrations of several elements both in soils and in plants. An excess of bioavailable potassium (K) in soil led to significant increase of K and deficiency of calcium (Ca) and magnesium (Mg) in all parts of T. aestivum. Concentrations of many other elements in the plants also changed. The effects of soil fertilization on plant biomass, leaf chlorophyll, and plant element concentrations were soil-dependent. Depending on the ratio of K/Mg in the soils, there was either an increase of plant yield and chlorophyll content or no effect at all.