The level of yielding and biological capacity of grass mixtures of feeding crops (common ryegrass (Lolium perenne); spring vetch (Vicia); Austrian winter pea (Pisum arvense); blue lupine (Lupinus angustifolius); common barley (Hordeum vulgare)) in the conditions of the Northern part of the Republic of Belarus and their quality evaluation were studied. The optimum temperature of seed germination at the seeding depth and the sufficient amount of moisture in soil provided high germination rate. Nitric fertilizer application and crop sowing in the conditions of various coenosis did not affect seed germination. The quantity of shoots predetermined the optimum plant stand density and made it possible to generate high green mass productivity. Formation of a high green mass yield in single-crops sowings of annual ryegrass was obtained against the background of minimum 180 kg of primary nutrients of nitric fertilizers per 1 ha, taking into consideration that the amount of crop tops increases in 3 times in comparison with crops without nitric fertilizers. Inclusion bean component into the grass mixture (even without nitrogen application) made it possible to generate the level of top biomass by three hay crops from 40,2 up to 55,4 t/ha. However, application of mineral nitrogen for cultivation of leguminous and cereal crop mixtures with overgrassing of annual ryegrass made it possible to increase the green mass productivity. Inclusion of a bean component into a grass mixture rendered influence on the amount of digestible protein. The highest protein yield was provided by high yielding crops with content of spring vetch on the background of mineral nitrogen (0,9 t/ha). In coenosis with pea and lupine mixtures provided protein content of 0,8 t/ha