Nitrogen is among the most needed nutrients in wheat plays a key role in the crops’s reaching its maximum yield potential. Producing cultivars of high yield and high grain protein content is important. In order to investigate Nitrogen Utilization Efficiency (UTE), Nitrogen Uptake Efficiency (UPE), and Nitrogen Use Efficiency (NUE) and to determine the relationship among these factors and grain protein as well as yield, an experiment was conducted during 2002-2003 growing season in Arak. The expriment was established in a randomized complete block design of three replications. Treatments included six winter wheat cultivars which had been released in Iran during the past 50 years. Results indicated that the modern cultivars (Qods, Alamout and Navid ) benefitted from a more pronounced increase in biomass yield, grain yield and NUE in comparison with the old cultivars (Omid, Bezostaya and Azadi). However, UPE and UTE were not significantly different among the cultivars. On the other hand, grain protein concentration in modern cultivars was significantly lower in recent cultivars than in old cultivars probably because of the negative correlation that usually exists between grain yield and grain protein content.
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