Food grain production per capita in the whole of Russia, including in the Mari El Republic is not enough. Therefore, one of the main tasks of agriculture is to increase grain production. In the Mari El Republic among spring cereals important food is the significance of spring wheat. Development of actions that improve grain yield of spring wheat, is one of the main tasks for agricultural science and practice. Among the techniques of increasing the yield of wheat an important place should be given to proper applica-tion of fertilizers taking into account biological features of culture, soil fertility and growing conditions. These studies have been conducted at the base of the experimental field of the Mari State University in 2014. The aim is to study the influence of timing and doses of nitrogen fertilization on the yield formation of spring wheat. Norms of fertilizers were calculated by the balance method for obtaining 3,5 tons of grain per 1 ha. Triple superphosphate, potassium sulfate and ammonium nitrate were used as fertilizers. The study revealed that nitrogen fertilization increases photometric indicators of spring wheat. Net productivity of photosyn-thesis was at its maximum during the period of stem elongation-earing. In the variants with application of nitrogen fertilizing, the participation rate was higher than the control by 3,7–4,7 g/m2 of leaf surface per day. Nitrogen fertilization significantly increased grain yield of spring wheat. Contributes to the control amounted to 1,31–1,47 t/ha depending on the variant. Analysis of yield structure of spring wheat revealed a positive influence of mineral fertilizers on the productivity elements of culture.