TY JOUR TI CHANGES IN THERMAL RESOURCES OF THE VEGETATION PERIOD AND PRODUCTIVITY OF SPRING WHEAT IN THE CONDITIONS OF THE MIDDLE VOLGA REGION KW spring wheat (Triticum aestivum) KW gray forest soil KW yield KW air temperature KW sum of effective temperatures KW yield correlation JO Vestnik of Kazan State Agrarian University AU Serzhanova, A.R. AU Gilyazov, M.. AU Shaykhutdinov, F.. AU Serzhanov, I.. AU Daminova, A.I. PY 2023 IS 18 PB Kazan state agrarian University