Effect of row spacing on grain yield and its components and radiation use efficiency in four rapeseed (Brassica napus L.) cultivars grown in paddy fields in Guilan

The effect of row spacing on grain yield, yield components and oil content of four rapeseed (Brassica napus L.) cultivars was investigated in a paddy fields as second crop after rice at Rice Research Institute of Iran (Rasht), in 2003-2004 and 2004-2005 cropping seasons. The experiment was conducted as a split plot arrangement in a randomized complete block design with four replications. Four rapeseed cultivars: Hyola308, RGS003, PF7045/91 and Hyola401 were assigned to main plots and three row spacings: 20, 25 and 30 cm at constant plant densities` (40 plant/m2) were randomized in sub-plots. Results showed that rapeseed cultivars were significantly different in grain yield, oil content, oil yield, biological yield, days to maturity, number of siliques per plant, number of grains per silique, silique length, 1000- grain weight, number of first, second and third order auxiliary branches, and plant height. Results also indicated that, PF7045/91 ranked the first in grain yield, oil content, oil yield, biological yield, days to maturity, number of siliques per plant and number of first and second order branches and plant height. Row spacing had significant effect on biological yield, harvest index and days to maturity, but its effect on grain yield, oil content and oil yield was not significant. However, row spacing of 20 cm ranked the first in grain yield, oil content, and oil yield. Correlation coefficients between traits indicated that grain yield was significantly correlated with number of siliques per plant, second order branches and plant height. Number of siliques per plant and plant height were significantly correlated with oil content. Results showed that PF7045/91 ranked the first in light interception (LI%) and radiation use efficiency (RUE) (75.5% and 2.33 g.MJ-1, respectively) and Hyola308 ranked the least (61.5% and 1.54 g.MJ-1, respectively). Row spacing of 20 cm also ranked the first in light interception (68.5%).