Effects of chemical nitrogen fertilizer sources on seed yield and some agronomic characteristics of winter rapeseed cultivars (Brassica napus L.) in Arak (Iran)

To evaluate the effects of nitrogen fertilizer sources on seed yield and some agronomic characteristics of different winter rapeseed (Brassica napus L.) varieties a split plot field experiment، arranged in complete block design with three replications was carried out in Agricultural and Natural Resources Research Center of Markazi Province، Arak (Iran)، during 2009-2010 growing season. Three nitrogen sources (2-Amonium Phosphat، Amonium Nitrat and Urea) and five rapeseed varieties (Okapi، Modena، Licord، SLM046 and Talayeh) were randomized in main plots and sub-plots، respectively. In this research، the interaction effects between urea fertilizer × Modena variety and 2-Amonium Phosphat × Talayeh showed the highest seed and oil yield per unit area، respectively. Talayeh variety produced the greatest seed oil content as affected by 2-Amonium Phosphat fertilizer in comparison with Modena variety. Hence، the positive relationship was observed between oil yield per unit area and seed yield in rapeseed. The interaction effect between urea fertilizer × Modena variety increased seed yield due to increment of biological yield، length of flowering period، days to end of flowering. The interaction effect between 2-Amonium Phosphat × Talayeh variety enhanced seed yield by means of increasing the length of maturity، plant growth period and harvest index. Inaddition، 2-Amonium Phosphat × Modena variety showed the the highest numbers of siliques per plant and the lowest seed yield per unit area. In this study، There was positive and significant correlations between seed yield and biological yield (r=0. 91**) and harvest index (r=0. 61**). Also، correlation coefficient between oil yield and seed yield (r=0. 98**) and seed oil content (r=0. 58**) was positive and significant.