Response of bread wheat to nitrogen application in calcareous soils of western Iran.

3 Abstract: This research was done for determining the effect of application nitrogen rates on yield and yield components of three wheat cultivars in calcareous soils of western Iran. Experiment was conducted as split plot and randomized complete block design (RCBD) with three replications in 2007-2008. The main plots were three cultivars (Chamran, Verinak and Dez) and subplots were nitrogen rates (0, 80, 160 and 240 kg/ha). The results showed that yield, yield components and associated traits had significantly effect by treatments. The highest and lowest grain yield obtained by Chamran and Dez cultivars, respectively. The results showed that effects of nitrogen rates on yield and yield components were significant. Grain yield, number of spikes/m , 2 number of grains per spike, harvest index and protein content increased as polynomial second order by increasing nitrogen rates. The highest grain yield and biologic yield were obtained in 160 and 240 kg/ha with 5100 and 14360 kg/ha, respectively. Decrease of grain yield compared to biological yield in treatment of application of 240 kg/ha was due to decrease of number of spikes/m and number of grains/spike. 2