TY JOUR TI COMPARATIVE PRODUCTIVITY OF SUNFLOWER HYBRIDS UNDER THE APPLICATION OF GROWTH BIOSTIMULANTS UNDER THE CONDITIONS OF SAMARA REGION KW sunflower KW hybrids KW growth biostimulants KW Aminokat KW Raikat Razvitie KW Kelkat boron KW productivity KW oil content JO Vestnik of Kazan State Agrarian University AU Kiseleva, L.V. AU Vasin, V.G. AU Zhizhin, M.A. PY 2020 IS 14 PB Kazan state agrarian University