1st Central Asia Congress on Modern Agricultural Techniques and Plant Nutrition, Kyrgyzstan, 1 - 04 October 2013, vol.2, no.2, pp.1495-1502
Growth and development of wheat from germination and emergence to maturity are controlled by Growing Degree Days (GDD) or total heat unit. Required heat should be accumulated slowly in long run with the optimum growth temperatures for wheat (10-24 °C). Such a proper accumulation increases the number of tillers and size of leaves and spikes. In present study, effects of sowing times on total GDD values of wheat were investigated. Experiments were conducted in randomized blocks-split plots experimental design under dry conditions of Erzurum during the cropping years of 2002-03 and 2003-04. The local wheat cultivar Kırik was used as the plant material. There different sowing period (winter, freezing and spring) were used in experiments. Effects of sowing dates on required GDD values for bolting, flowering and physiological maturity periods were significant in both years. Required GDD values for bolting in winter, freezing and spring sowings were respectively determined to be 1191.1, 531.7 and 384.4 in the first cropping year and 1161.3, 550.4 and 407.7 oC in the second cropping year; the values for flowering were 1468.2, 953.5 and 942.7 in the first cropping year and 1461.7, 930.6 and 889.3 °C in the second cropping year; the values for physiological maturity were 2009.0, 1465.6 and 1407.4 in the first cropping year and 2009.0, 1424.3 and 1376.3 °C in the second cropping year. GDD values required for growth stages decreased with delays in sowing periods.