changes in yield and yield components of four cultivars of barley under different nitrogen levels in isfahan region

In order to study the effect of different nitrogen levels on yield components and seed yield of three barley cultivars, an experiment was conducted in 2011-2012 in a research farm of farming building of islamic azad university khorasgan (isfahan) branch located in khatunabad village (latitude 32o /40' n and longitude 51o /48' e). a split plot layout within randomized complete block design with 3 replications was used. main plot were different level ofnitrogen fertilizer (0, 75and 150 kg ha^-1) from urea source, and sub plot were different cultivars (reyhan03nosrat, valfajr and yousef). condition represented the effect of nitrogen was significant on number of spikes m^-2, seed yield, biological yield and harvest index.50 kg n ha^-1fertilizer treatment, resulted the maximum of all mentioned factors except biological yield. effect of cultivar was significant on number of spikes m^-2 and biological yield. the maximum of all mentioned factors related to valfajr cultivar.interaction of nitrogen and cultivar was significant on number of spikes m^-2, seed yield andharvest index. on the basis of the results obtained, the fertilizer treatment 50 kg n ha^-1 and valfajr cultivar might be suitable for barley productive under the condition similar to the present study.