The research was based in Experimental Station of the Department of Grassland and Natural Landscape Sciences at Poznań University of Life Sciences located in Brody Experimental Farm. Research on the influence of various doses of nitrogen fertilizer N-14, Physioactiv, Physiostart and PinKstart fertilizers applied in grass-legume mixture was conducted in the years 2016-2017. The following variants and doses of fertilizers were applied in the experiment: 1/ 300 kg·ha-1 N-14 under each regrowth (total of 900 kg·ha-1) + PK; 2/ 300 kg·ha-1 N-14 under the first regrowth and 180 kg·ha-1 of ammonium nitrate 34% N under the second and the third regrowth + PK; 3/ standard fertilization – 180 kg·ha-1 of ammonium nitrate 34% N under each regrowth + PK; 4/ Physioactiv fertilization in a dose of 300 kg·ha-1 before vegetation and 180 kg·ha-1 of ammonium nitrate 34% N under each regrowth + PK; 5/ Physiostart in a dose of 20 kg·ha-1 before vegetation and 180 kg·ha-1 of ammonium nitrate 34% N under each regrowth + PK; 6/ PinKstart in a dose of 20 kg·ha-1 before vegetation and 180 kg·ha-1 of ammonium nitrate 34% N under each regrowth + PK; 7/ absolute control – no fertilization. The highest yield of a dry matter of a grass-legume mixture in the two years of utilization was a result of an application of a nitrogen fertilizer N-14 which was applied under every regrowth and in a variant of application just under the first regrowth, together with a dose of phosphorus and potassium. A biological additive on the basis of sea algae (Pheoflore complex) in N-14 fertilizer resulted in higher yields of the sward, despite smaller dose of nitrogen when compared to variants fertilized with ammonium nitrate. An application of a calcium fertilizer Physioactiv with aminopurine resulted in an increase in a share of white clover in the sward and in a better nutrition of plants with nitrogen which was visible in the highest values of a leaf blades greenness index both in the case of white clover and perennial ryegrass. It may be presumed that the positive effects of the application of the analyzed fertilizers might originate from their formulation due to the joint of mineral components used in traditional fertilizers with biological additives which stimulate a root system, activate soil’s flora and therefore enhance the state of rhizosphere.