Effect of planting date and seeding rate on grain yield and yield components in two rapeseed (Brassica napus L.) cultivars under Sistan conditions

In order to study the effect of sowing date and seeding rate on grain yield and yield components two rapeseed (Brassica napus L.) cultivars, a field experiment was carried out using a split plot factorial arrengements with three replications at the Zahak Agricultural Experimental Station, Zabol, Iran in two cropping seasons (2004-2006). Sowing dates were assigned to main plots at four levels (5 October, 20 October, 5 November and 20 November). Combination of two spring rapeseed cultivars (Hyloa401 and RGS003) with three seeding rates (6, 8 and 10 Kg/ha) were randomized in sub-plots. Results showed that sowing date had significant effect on grain yield and yield components (number of silique in plant, number of seed in silique, 1000 grain weight) and other studied traits.With delay in sowing date grain yield decreased 3.4 percent per week.The highest grain yield with mean of 3943 Kg/ha obtained in second sowing date (25 October) and the lowest grain yield with mean of 1830 kg/ha in fourth sowing date (15 November).The effect of cultivar, except number of seed in silique, plant height and oil content, was not significant on the other components and traits. RGS003 cultivar with mean of 3249 Kg/ha performed better than Hyola401 with mean of 3062 Kg/ha. The effect of seeding rate, except on 1000 grain weight and plant height, was not significant on the other components and traits. Nevertheless, the highest grain yield with mean of 3282 Kg/ha was obtained from seeding rate of 10 Kg/ha. Interaction of sowing date × cultivar on number of silique in plant, interaction of seeding rate × cultivar on plant height and interaction of sowing date × seeding rate × cultivar on 1000 grain weight, were significant. It is concluded that sowing date of 20 October for RGS003 and Hyloa401 cultivars and seeding rate of 10 Kg/ha can be recommended for conditions of Sistan region.