Effects of Seeding Rate on Important Agronomic Traits in Three Winter Rapeseed (Brassica napus L.) Cultivars

To evaluate the effect of seeding rate on important agronomic traits in three winter rapeseed (Brassica napus L.) cultivars, two field experiments were carried out as split plot arrangement in a complete block design with three replications during 2006-2008 growing seasons. Three rapeseed cultivars (Okapi, Modena and Licord) and three seeding rates (6, 8 and 10 kg/ha)) were randomized in main plots and in sub-plots, respectively. The results revealed that rapeseed cultivars had significant differences for all traits except for grain oil content. Licord had the highest grain yield (4213.72 kg/ha), harvest index (31.07%), and biological yield (13071.4 kg/ha). Significant differences were observed among different seeding rates for some such traits as grain number per silique, silique number per plant, plant height, secondary branch number per plant, days to maturity, grain yield per plant, and dry matter remobilization. The highest grain yield and dry matter remobilization were obtained for the 6 kg/ha seeding rate treatment. Increased seeding rate diminished grain yield, yield component and dry matter remobilization from the aboveground plant parts to grain. Licord had the highest grain yield and harvest index on 8 (88 plants per m2) and 6 (66 plants per m2) kg/ha seeding rates, respectively. There were positive significant correlations between grain yield and the most of the traits namely 1000-grain weight, grain number per silique, silique number per plant, plant height, secondary branch number per plant, days to maturity, maturity duration, grain oil content, oil yield, grain protein content, harvest index, biological yield, grain yield per plant and dry matter remobilization. Also the correlation coefficient between dry matter remobilization and all the traits except days to end of flowering and grain oil content was positive and significant. According to the results obtained in this experiment, it seems that Licord variety accompanied by the 6 kg/ha seeding rate to be recommendable in Arak region, as well as in similar agroecological conditions.