Interaction of N Residues of Maize Cropping and N Fertilizer on Seed and Oil Yield of Rapeseed

In order to determine the interaction of residual nitrogen (N) and different N rates on seed and oil yield of rapeseed, an experiment was conducted at Shahrekord University, Shahrekord, Iran, in 2008-2009 growing season. The experimental design was split plots arranged in randomized complete block design with three replications. Seven treatments of residual N (217, 435 and 652 kg/ha from urea fertilizer; 6.1, 12.2 and 18.3 ton/ha from broiler litter; and control: no-fertilizer) as main plots, and different levels of nitrogen (0, 60, 120 and 180 kg/ha N) as subplots were compared. Results showed that the highest number of seeds per pod and 1000-seed weight were obtained with residual N of 12.2 ton/ha as broiler litter of previous cropping. The applied N in rapeseed cropping resulted in a significant increase in number of seeds per pod, but oil content was significantly decreased. A significant interaction was observed between N residues of previous crop and applied N on number of pods per plant, seed yield and oil yield. The highest seed and oil yields were obtained with N residues of 12.2 ton/ha broiler litter and 120 kg/ha N in rapeseed cropping. In general, application of large amount of chemical fertilizer in maize cropping reduces the potential of rapeseed yield. However, application of broiler litter not only provides residual N for rapeseed, but also reduces fertilizer costs.