Effects of Different Temperature and Moisture Regimes on Oil Contents of Two Canola (Brassica napus L.) Cultivars

The effects of different temperature and moisture regimes on oil content of two canola cultivars were evaluated at Agricultural Research Station of Gonbad in a 2-year study. The experiment was a randomized complete block design arranged in a split-plot in two conditions, i.e. supplemental irrigation and rainfed. Five sowing dates (6 Nov., 6 Dec., 4 Jan., 5 Feb. and 5 Mar.) were as main plots and two cultivars (Hyola 401 and RGS003) were as subplots. In both years, increase in seed yield was associated with increase in oil percent. In overall, oil percent and yield varied considerably (28.0-43.1% and 46-1715 kgha-1, respectively. Supplemental irrigation increased oil yield of canola, due to increase in seed yield and oil percent. There was a significant quadratic relationship between oil percent and used water in evapotranspiration during growth season, explaining 74 and 66% of the variation for Hyola 401 and RGS003, respectively. A great proportion of the variation in canola oil percent was related to environmental conditions during seed filling period. The increase of air temperature during critical period of seed filling, particularly at sowing date of 5 March, decreased oil percent. There was a significant negative relationship between mean air temperature during seed filling period and oil percent, explaining 82 and 77% of the variation for Hyola 401 and RGS003, respectively. Earlier sowing dates more closely matched seed filling period of the crop to optimum weather conditions, led to an increased oil percent, and an increased oil yield