Two field trails were carried out at Sakha Agricultural Research Station Farm through the two successive growing seasons of 2006/2007 and 2007/2008 to study the effects of fertilization with five nitrogen levels of 0, 25, 50, 75 and 100 kg N/fed. and applying azospirillum bacteria as effective biofertilizer on yield, yield components, nitrogen percentage and grain protein content of wheat .Split plot design was used, the main plots were assigned by N levels and the sub plots were assigned by biofertilization. The obtained results can be summarized as follows: Inoculation with biofertilizer high significantly increased wheat grain yield from 1.32 to 2.13 ton fed.^-1 in the first season and from 1.31 to 2.2 ton fed^-1 in the second season. Increasing nitrogen fertilizer rates high significantly increased grain yield. The highest mean values of 2.26 and 2.6 ton fed^-1 were obtained with 100 kg N fed^-1 in the first and second season, respectively. Obtained data clearly illustrated that the mean values of straw yield tons/fed. were increased by increasing nitrogen does up to 100 kg/fed. The highest mean values were recorded and they are 3.03 and 3.12 ton/fed. in the first and second growing seasons, respectively. On the contrary, the lowest mean values were recorded under the control treatment (without nitrogen) of 1.32 and 1.28 ton/fed. in the two growing seasons. The mean values of nitrogen and protein percentages were increased by increasing both of mineral and biofertilizer applications. The mean values for plant height were increased by increasing application of both mineral and biofertilizer. The mean values under biofertilizer application were 96.36 and 97.23 cm. But under non-application treatments the mean values were 62.12 and 61.04 cm in the first and second seasons, respectively. Also, application of
mineral fertilizer up to 100 kg/fed. increased wheat plant height. The highest mean values were recorded with 100 kg N fed.^-1. The mean values of 1000 grain weight, number of tillers and number of spikes were incased by increasing nitrogen dose up to 100 kg N/fed. Also, application of biofertilization led to increasing the studied parameters in comparison with non-application treatments.