اثر مصـرف مقادیر مختلف نیتـروژن بر فتوسنتز جـاری و انتقال مجدد ماده خشک دو رقم کلزا (Brassica napus L.)

To study the effect of different amounts of nitrogen fertilizer on dry matter remobilization in two cultivars of rapeseed a factorial experiment was conducted in complete randomized block design with three replications in the 2010-2012 years in Rasht, Iran. The experimental factors were two cultivars of rapeseed (Sarigol and Hayola308) and nitrogen fertilizer rate (from urea source) at five levels of 0, 50, 100, 150 and 200 kg ha-1 of N as 1/3 at planting 1/3 at stem elongation 1/3 before flowering. The results indicated that in the second year a higher dry matter remobilization (400 g m-2), current photosynthesis (1750 g m-2) and grain and oil yield (2149.8 and 927.2 kg ha-1 respectively) was achieved. Between nitrogen rates, application of 200 kg N ha-1 led to the highest current photosynthesis, dry matter remobilization, grain and oil yield. Hayola308 cultivar with 150 and 200 kg ha-1 of N indicated the highest oil yield (1518 and 1333 kg ha-1, respectively) and dry matter remobilization (531.5 and 492.4 g m-2 respectively). According to the results of the present experiment, it seems that cultivar Hayola308 with application of 150 kg N ha-1 can increase the current rate of photosynthesis, dry matter remobilization and oil yield of rapeseed, due to increase in the photosynthetic surfaces.