The objective of the study was to elucidate correlations between meadow plant species, the content of some biogenic elements in groundwater, sward harvesting frequency and the level of the groundwater table at the beginning and at the end of a growing season. An adequate choice of species grown in organic soil may be of particular significance for nutrient management and prevention of water eutrophication due to biogenic elements. A lysimeter experiment was conducted on peat-muck soil. The chemical composition of groundwater sampled underneath the rhizosphere of P. pratensis, Ph. pratense and L. perenne was assessed in several years. Two fixed levels of the groundwater table were maintained in the lysimeters: 50 and 90 cm below the ground surface. Grass was harvested three or five times during a growing season. The content of nitrate-nitrogen and ammonium-nitrogen, phosphorus, potassium, calcium, sodium and magnesium was determined in the analysed groundwater. The results showed significant variation in the mean (over the research period) content of selected mineral components (except for phosphate ions) in the piezometer water collected under the rhizosphere of specific grass species. The species L. perenne absorbed mineral components most effectively. The highest concentration of the majority of the components studied was found in water beneath the rhizosphere of P. pratensis. Significantly higher concentrations of calcium, magnesium, sodium, phosphorus, nitrate-nitrogen (but not ammonium-nitrogen) and potassium were found in water in the springtime. The biogenic element content found in objects with a three-cut harvesting regime was lower than in waters underneath grasses harvested five times. Regardless of the species and harvesting frequency, a significantly higher content of specific cations and anions in piezometer water was found in objects with a lower level of the groundwater table.