Study of Possibility of Delayed Planting of Oilseed Rape (Brassica napus L.) in East Azarbaijan in Iran

Suitable planting date, with providing essential growth rate, in oilseed rape leads to higher seed yield by decreasing cold damages. A field experiment was conducted in factorial arrangment with two factors including: four planting date (12 and 23 September and 2 and 12 October) and five cultivars (Modena, Licord, Okapi, Opera and Zarfam) using randomized complete block design with three replications in Khosrosharh field station, Tabriz, Iran, in 2008 to 2010 croppping seasons. Results showed that cultivars in late planting date (12 Oct.), in comparison with suitable planting date (11 Sep.), had significantly less leaves and crown diameter when approaching average air temperature below base temperature (5 ºC) for oilseed rape and showed significantly higher cold damage (%). Pod number per plant and seed yield decreased in delayed planting. It was concluded that 11-23 Sep. is the suitable planting period in Tabriz plain and areas with similar climatic conditions. Correlation coefficients between leaf no. per plant, crown diameter and cold damage with each other and with seed yield were significant. Therefore, oilseed rape plants with at least 5 leaves and 6 mm crown diameter before occurence of freezing temperatures showed less damage from cold and freezing stresses and were able to produce higher seed yield. Pod number per plant had positive significant correlation with 1000 seed weight and seed yield. These oilseed rape cultivars showed suitable for being grown in Tabriz plain and areas with similar climatic conditions.