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