Response of Oilseed Rape Hybrids and Promising Lines to Sowing Date in Gorgan Area

To study the effect of sowing date on yield, yield components and agronomic traits of oilseed rape promising hybrids and lines, an experiment was conducted at Agricultural Research Station of Gorgan during 2010–2011 and 2012-2013 cropping seasons. The experiment was a randomized complete block design arranged in split plot. Four genotypes Hyola 50, Hyola 420, L5 (Varamin) and L6 (Zabol) were as sub plots and five sowing dates 23 Oct., 11 Nov., 1 Dec., 21 Dec. and 10 Jan., were as main plots. The mean air temperature during germination time for sowing dates 23 Oct., 11 Nov., 1 Dec., 21 Dec. and 10 Jan was 19.5, 14.7, 13.8, 8.8 and 6.8 oC in 2010–2011, and 20.5, 15.1, 12.2, 6.8 and 8.56.8 oC in 2010–2011, respectively. In both years, seed yield, aboveground dry matter and harvest index decreased with delay in sowing date. In the first year, the first sowing date had the highest (4070 kgha-1) and last sowing date had the lowest (2323 kgha-1) seed yield. Similarly, in the second year, the first sowing date had the highest (4125 kgha-1) and the last sowing date had the lowest (2319 kgha-1) seed yield. The mean seed yield of Hyola 50, Hyola 420, L5 and L6 was 3534, 3329, 2977 and 3147 kgha-1, respectively. The mean harvest index of Hyola 50, Hyola 420, L5 and L6 was 30.6, 29.2, 27.9 and 29.1%, respectively.