abstract: The two-year pot experiment (in a greenhouse) was set in completely randomised pattern. The aim of presented study was to evaluate the influence of bed after mushroom production and complementary mineral nutrition (nitrogen-potassium) on iron, manganese and boron content of Italian ryegrass. The content of determined elements in the biomass of Italian ryegrass was differen-tiated in the years of experiment as well as between the cuts, and ranged from the highest to the lowest: Fe > B > Mn. In biomass of Lolium multiflorum from objects fertilised with bed after mush-room production with an addition of mineral fertilisers the lowest amount of iron, highest of manga-nese and boron was determined compared to the objects fertilised with FYM.