Effect of nitrogen fertilizer levels and row spacing on grain yield and morphological characteristics of rapeseed as second cropping after rice

The effect of nitrogen fertilizer levels and row spacing was studied on grain yield and morphological characteristics of rapeseed (Brassica napus L., var. Hyola 308) as second cropping in paddy fields of Rice Research Institute of Iran. experiment was carried out for two years as factorial based on a randomize complete block design with three replications. The first factor was four nitrogen fertilizer levels from urea including 98, 140, 182 and 224 kg.haP -1 P. The second factor was row spacing at three levels of 20, 25 and 30 cm. In this experiment, some important growth characteristics such as plant height, number of siliques per plant, number of seeds per silique, biological yield, harvest index, grain yield, oil yield, initiation of flowering and growth periods were studied. Results of the combined analysis of variance showed that there were no significant difference for grain yield between the two experimental years. Between nitrogen levels, the treatment of 224 kg haP -1 Pproduced maximum grain yield (2189 kg haP -1 P), oil yield (1001 kg.haP -1 P), biological yield (7142 kg.haP -1 P), plant height (111.9 cm) and height of the lowest silique bearing branch from soil surface (34.4 cm). Row spacing of 20 cm showed the highest grain yield (1947 kg.haP -1 P), oil yield (887.4 kg.haP -1 P), biological yield (6652 kg.haP -1 P) and plant height (109.9 cm). Although the interactions between nitrogen levels and row spacing was not significant, maximum grain and oil yields were obtained by application of 224R Rkg.haP -1 P nitrogen fertilizer in 20 cm row spacing.