The field experiment with three species of grasses in different water conditions was carried out in 2005-2008 in the experimental fields in Złotniki near Poznan, a subsidiary of Experimental- Educational Laboratory for Soil and Plant Cultivation, University of Life Sciences in Poznan. The aim of the study was to elaborate a nitrogen balance, using common indicators of uptake and based on laboratory confirmed nitrogen content in plant material. On this basis, both developed balances were confronted. In conducted study it was found that the calculation of the amount of nitrogen taken with the use of generally accepted factors was understated in relation to the actual uptake. In the option with sprinkling irrigation, regardless of species, the applied dose of 180 kg of nitrogen was almost entirely used by plants, but in the option without sprinkling irrigation, nitrogen balance was obtained after the application of about 120 kg N ha-1.