Two field experiments were conducted at El-Gemmaiza Agricultural Research Station farm, middle Delta, region Egypt 30º  43^- latitude and 31º 07^- longitude during the two successive summer seasons of 2012 and 2013 to study the effect of different rates of nitrogen, biofertilizer and their combinations on yield, yield attributes of maize (cv three way cross 324), N, P and K content and available nutrients in the soil. . Split Split plot design was used with three replicates. The main plots were assigned for three nitrogen fertilization levels (80, 100 and 120 kg N fed ^-1), the sub plots were assigned with three inoculation treatments (without inoculation, inoculation with isolate 1 Azospirillum and inoculation with isolate 2 Azospirillum). The sub sub plots were assigned for three spraying Azospirillum treatments (without spraying, spraying with isolate 1 and spraying with isolate 2). The obtained results can be summarized as follow: Nitrogen fertilization level (80 kg N fed ^-1 ) produced the highest values of corn grain yield (32.26 ardb fed ^-1), stalk yield (10.14 ton fed ^-1 ), 100 grains weight (41.15g), N % in the grains (1.82%), protein % and content in the grains, the highest T.B.C (total bacterial count), Azospirillum count and catalase activity. Meanwhile nitrogen fertilization level of 120 kg N fed ^-1   had the lowest grain yield, stalk yield, protein % and content. Inoculation with isolate 2 Azospirillum had the highest grain yield (32.53 ardb fed ^-1), the highest N (2%), P (0.52%) and K (1.14%) in grain, the highest T.B.C, Azospirillum count and catalase activity comparing with isolate 1 and without inoculation treatments. Spraying with isolate 2 Azospirillum gave the highest corn grain yield, stalk yield, 100 grain weight, protein % and content, T. B. C, Azospirillum count and catalase activity. The interaction of 80 kg N fed ^-1 + inoculation with Azospirillum isolate 2 + spraying with isolate 2 Azospirillum had the highest values of the studied parameters. The treatment 100 kg N fed ^-1  gave the highest available P after harvesting (7.04 ppm), T. B. C, Azospirillum count and catalase activity, while the treatment of 120 Kg N fed ^-1 had the highest available K in the soil after harvesting.