The study dealt with the evaluation of the productive efficiency of water for selected grass species under different ground water levels and grass mixture species composition. The productive efficiency of water was estimated based on lysimetric measurements of 2001-2003 which involved Poa pratensis¸ Phleum pratense and Lolium perenne in pure stand as well as P. pratensis with Ph. pratense and P. pratensis with L. perenne mixtures. Grasses developed under constant levels of ground water (50 and 90 cm). The same level of mineral fertilization was applied for all the treatments. The results demonstrate that the mean productive efficiency of water for the vegetation period at Sosnowica ranged from 1.6 to 3.2 g dm·m^-2·dm^-3 of water and varied depending on the botanical composition of the sward and the ground water level. At lower ground water level (90 cm), two-species communities and P. pratensis and its mixture with Ph. pratense at a higher water level (50 cm) showed the highest efficiency. Water was used least effectively by L. perenne sward. Keeping a high level of ground water decreased the productive efficiency of water. Significant dependences between the yield and the productive efficiency of water were found.

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