عنوان مقاله [English]
Effects of different amounts of four nitrogen fertilizers sources on seed and oil yield of rapeseed cv. SLM046, and nitrogen residues in the soil were studied after harvesting. An experiment was conducted at Zanjan Agricultural Research Center, in 2004. A factorial experiment based on a randomized complete block design with three replications was used. Five levels of N comprised of 0, 60, 120, 180 and 240 Kg of net nitrogen/ha and fertilizer sources of sulfur coated urea (SCU), urea (U), ammonium nitrate (AN), and ammonium sulphate (AS) were used at three stages: planting time, stem elongation and seed setting, but U fertilizer was applied at the planting time. The highest seed and oil yield were obtained for UN240. The highest N residues were found for SCU fertilizer. An increase of nitrogen (N) ranges from 0 to 240 kg/ha incraesed N residues in the soil. In addition, more NO3- was observed by applying AN, U, and SCU as compared with SA. The highest and the least NH4+ in soil was detected when fertilizers SCU and AN were applied, respectively. In general, despite of different N applications in rapeseed, amounts of NO3- and NH4+ residues in soil were lower than of those before planting, indicating high potential of rapeseed crop in N absorption. It was also revealed that increase of applied N was in contradictory with nitrogen uptake efficiency. NA fertilizers showed the highest and SCU the lowest nitrogen uptake efficiency in rape seed crop.