TY JOUR TI PRODUCTIVITY AND QUALITY OF MEDIUM-RIPED POTATO TUBERS DEPENDING ON THE DOSES OF PHOSPHOROUS FERTILIZERS ON THE GRAY FOREST SOIL OF FOREST-STEPPE OF THE MIDDLE VOLGA REGION KW microelements KW phosphorus KW mineral fertilizers KW productivity KW potatoes KW vitamin C KW starch KW protein KW nitrates JO Vestnik of Kazan State Agrarian University AU Vladimirov, V.P. AU Egorov, L.M. AU Artamonov, S.G. PY 2019 IS 14 PB Kazan state agrarian University