In order to effect of supplemental irrigation and nitrogen levels on yield and yield components of two wheat cultivars were performed a experimental at farm of Campus of Agriculture and Natural Resources, Razi University in Kermanshah in 2008-2009. Treatments included supplemental irrigation as the main plot at 4 levels (control (non irrigation) and irrigation during booting, anthesis and grain filling), nitrogen as a sub plot at 4 levels (0, 50, 100 and 150 kg ha-1 N net from urea source) and two wheat cultivars "Sardari" and "Cross-Alborz" as sub-sub plots. Experiment was a randomized complete block design with four replications. The result showed the effect of supplementary irrigation, N rate ant cultivar on grain yield were significant. The highest of grain yield obtained in supplemental irrigation at anthesis and booting stages with 362.2 and 352.0 g m-2, respectively . This influenced by increasing the number of spikes per unite area and thousand grain weight, but had not effect on the number of grain per spike. Using of 50 kg ha-1 N, with increasing grain number per spike and thousand grain weight produced the highest grain yield (335.0 g m-2). "Cross-Alborz" (337.8 g m-2) relative to "Sardari" (298.2 g m-2) indicated advantage grain yield. "Cross Alborz" in this experiment had the number of spikes m-2, the number of grains per spike, 1000-grain weight, plant height, peduncle length, the contribution of current photosynthesis, the contribution of stem reserves and straw spike reserves more than "Sardari".
