The experiment with natural meadow of Agrostis capillaris - Festuca fallax type in Rhodope Mountains (Smolyan region, Southern Bulgaria) shows that according to fertilization variants there is a clear tendency towards earlier start of active vegetation and its next phenophases. Most and almost equal amounts of dry biomass (4.38 and 4.31 t.ha-1) were reported in fertilization with N160P80K80 and N160P80, which exceeded the unfertilized control by 128.12 and 124.48%, respectively. Compared with unfertilized variant, the crude protein content increased in all fertilizing variants, as in complete mineral fertilization with N80-160 accumulates the crudest protein - respectively 314 g.kg-1 and 318 g.kg-1. As regards to other studying chemical indicators of the forage (crude fiber, crude fat, crude ash and nitrogen-free extract substances) the mineral fertilization also had an expressed positive effect.