A field experiment was carried out at the experimental facility of the University of Natural Sciences and Humanities in Siedlce, Poland. The experiment was established in autumn 2018 and conducted for the next two years. Three biological fertilizers, based on, respectively, humus extract, vermicompost extract and compost extract, constituted the main experimental factor. In the experiment, each fertilizer was used on its own and in combination with mineral NPK fertilizers. The following grass species were used in the experiment: Dactylis glomerata, Lolium perenne and Festulolium braunii. According to scientific reports, biological fertilizers positively affect forage quality and quantity. Therefore, it was considered appropriate to study their effects further by comparing the content of macronutrients in selected grass species treated with biological fertilizers formed on the basis of beneficial microorganisms. The total content of P, K, Ca and Mg (g kg-1) in plant dry matter was determined by ICP-AES. Based on the results, the ratios of K:(Ca+Mg) and Ca:P were calculated. The treatment combinations had a various effect on macronutrient accumulation by the grass species. The application of humus extract significantly increased the P content in plant biomass. The application of mineral fertilization had a positive effect on the K:(Ca+Mg) ion ratio and the optimization of Ca:P. The combination of mineral fertilization with vermicompost extract significantly increased the K content in plants and improved the Ca: P ion ratio. The research results indicate that the use of biological fertilizers cannot replace mineral fertilizers. However, the combination of these two types of treatment led to positive results.

27.2.2022