Determination and investigation of sowing date effects on yield and phenoiogy of rape seed (Brassica napus L.)varieties

Sowing date is an important affecting factor on yield in rape seed (Brassica napus L.). However, the magnitude of yield reduction caused by delay in sowing has been poorly defined for different environments, in Kermanshah province. The present study was conducted to determine the effect of date of planting on grain yield and oil content in five cultivars of rape seed during 2000-01, and 2001-02 cropping season at moderate climate of Kermanshah, Islam Abad. The cultivars were compared in 4 different sowing date in a split plot design with 4 replications. Four sowing dates (27 August, 10 September, 25 September and 10 October) were considered as main-factors and the five cultivars (Orient, Tallaye, Okapi, SLMO 46 and Colvert) as the sub-factors. The combined analysis of variance indicated highly significant differences among the sowing dates and the cultivars. Other traits including: days to flowering, flowering period, plant height, days to maturity, seed per pod, oil content of seeds, were also different among the treatments. The effect of sowing date on yield, days to complete flowering and their interaction were different at 1 % level of significance. In the first sowing date (27 August), period of maturity and yield component were increased. In the first and the second sowing dates, the yield were highest with 3952 and 3478 kg/ha, respectively.Though the oil content was not increased in the first sowing date, but it was compensated for higher yield production. The highest grain yield were obtained form Orient and Cobra with 3289, 3235 respectively. The highest oil content belonged to Orient and Cobra, with 44.57% and 44. 2%, respectively.