A field experiment was carried out in the experimental farm , Collage of Agriculture and Veterinary Medicine, Thamar University, during two seasons (2008/2009 & 2009/2010) to study the effect of seeding rate and nitrogen fertilizer on yield of four promising varieties of barley. Split split plot design was used in RCBD with three replications, where barley varieties were randomly assigned to main plots, seeding rate to split plots and nitrogen levels to split split plots. Varieties had shown significant difference in number of spikes/m2, weight of 1000 kernels, grain yield and harvest index in both seasons. Moasasah 23 variety was the best variety. Increasing seeding rate to 110 kg/h resulted in a significant increase in number of spikes/m2, number of kernels/spike, weight of 1000 kernels, grain yield, biological yield and harvest index in both seasons. Nitrogen level increase to 120 kg/h resulted in significantly higher number of spikes/m2, weight of spike kernels, number of kernels/spike, weight of 1000 kernels, grain yield, biological yield and harvest index in both seasons. Interaction between cultivar Ary and Nitrogen (120 kg/h) have significantly increased weight of spike kernels and number of kernels/spike. Moasasah 23 and nitrogen (120 kg/h) interaction resulted in a significant increase of grain yield and harvest index. The interaction between seeding and nitrogen (120 kg/h) showed a significant increase in weight of 1000 kernels and grain yield in both seasons.

Key Words :Barley, Cultivar, Nitrogen, Seeds, Yield.