Losses of water and nutrients in drip irrigation system of greenhouse rose cultivation in peat substrate were presented in the paper. The outflows were measured using calibrated vessel method, on three dates when 2 or 3 irrigation cycles with various doses were applied. Moreover, the following laboratory assessments were made using reference methods in the averaged samples of nutrient solution and leachates: concentrations of 8 nutrients N–NH₄⁺, N–NO₂^–, N–NO₃ ^–, PO₄ ^3–, K⁺, SO₄ ^2–, Ca²⁺ and Mg²⁺. On the basis of measured leachate volumes and their nutrient concentrations, and basing on the volumes and concentrations of nutrients in nutrient solution supplied to the plants, computed were respectively loads supplied to and removed from the system, whereas the percent of nutrient losses was calculated from their ratio. Analysis of the research results revealed a high diversification of the leachate outflow volume depending on the amount of watering or daily dose and due to the number of cycles realized during the day. The paper demonstrated potential of decreasing water losses in the irrigation system, which depending on the calculation variant, under the experimental conditions ranged from 21.6 to 99.8%. An increase in concentrations of Mg²⁺, SO₄ ^2–, K⁺, and N–NO₂^– was also stated in comparison with the nutrient solution supplied to the plants, i.e. a phenomenon of so called condensation of leachates was observed. Due to this phenomenon, on average the highest, between 70 and 90% quantitative losses were noted for the same 4 nutrients. However, it should be emphasized that quantitative losses of nutrients occurred on each date of research and to various extent concerned all analyzed nutrients.

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