A significant part of bulky feed obtained from natural fodder lands is characterized by low quality due to the loss of valuable forage plants from herbage and non-observance of the terms and technologies of harvesting. Nutritional adjustment is an effective means of improving the composition of the herbage and the feed quality. To study the effect of various types and doses of fertilizers on the botanical composition and quality of forage for long-term hayfield at the FWRC FPA long-term field experiment has been conducted since 1947. For the 72-74th years, the use of hayfield without fertilizer application, with use of one- and two-component fertilizer and complete mineral fertilizer with a low dose of nitrogen, phytocenoses are formed with a predominance of short grasses, significant content of forbs and legumes (in technologies without the use of mineral nitrogen). The forage obtained from such grasslands meets the requirements of state standard specification for the first and second classes of hay of natural grasslands. Applying a complete mineral fertilizer with a nitrogen dose of N90-180, phytocenoses forms a predominance of high grasses. Considering the higher requirements of the standard for the hay of sown grasslands, the feed obtained from such grasslands mainly meets the second class ’s requirements. In all management systems, the second cut provides a higher quality of forage, which is associated with an increase after mowing in the content of well-leafed shoots of grasses and legumes. The authors noted the effect of weather conditions on the quality of hay. In years with favorable moisture conditions, the efficiency of the applied fertilizers increases, and the quality offeed improves.