TY JOUR TI OPTIMUM SOWING NORMS OF SUNFLOWER OF RODNIK VARIETY DEPENDING OF MINERAL NUTRITION BACKGROUND ON GREY FOREST SOILS OF THE MIDDLE VOLGA REGION KW sunflower KW productivity KW seed rate KW mineral nutrition background. JO Vestnik of Kazan State Agrarian University AU Safiollin, F.N. AU Nizamov , R.. AU Suleymanov , S.. AU Minnullin, G.. PY 2018 IS 13 PB Kazan state agrarian University