Quantifying nitrogen application in canola(Brassica napus L.) under optimum and late sowing dates

 In order to evaluate the influence of nitrogen fertilizer and sowing dates on agronomic characteristics, yield component and seed yield of rapeseed cultivar RGS003, two field experiments (separate) were carried out base on a randomized complete blocks design with three replications in 2014-15 and 2015-16 during growth seasons in research field of Islamic Azad University, Gorgan Branch. First experiment (November 9) and Second experiment (December 9), was performed, each one in 7 nitrogen levels (50, 75, 100, 125, 150, 175 and 200 kgN.ha-1). The analysis of variance results showed that sowing date and nitrogen fertilizer had significant effect at p<0.01 for pod per plant, seed per pod, 1000weight, biological yield, seed yield and harvest index. Highest (3128 kg.ha-1) and lowest (2414.95 kg.ha-1) seed yield was observed in 200 and 50 kgN.ha-1) treatments respectively. In two year, seed yield, biological yield and harvest index reduction at second sowing date was related to insufficient vegetative growth before flowering stage. Under present experimental conditions, planting on November 9 and usage of 175 and 200 kgN.ha-1 can be recommended as an appropriate date for obtaining the highest seed yield.