Biomass, nitrogen and grain yields of wheat cvs. Sakha 69 and Giza 163 as well as maize cv. single hybrid 122 were determined to eval- uate the response of gramineous crops to diazotroph inoculation, organ- ic and inorganic fertilization in Ismailia sandy soils. Rigorous environmen- tal conditions of the experimental site severely teflected on development of untrested plants which showed N deficiency symptoms at early growth stage. Ammonium sulfate was superior, compared to urea form-N, as the reported increases in biomass yield with the recom- mended N dose were 100 and 41.9% tor wheal cys. Sakha 69 and Giza 163, respectively. Response of both cultivars to diazotroph inoculation was found to be N-dependent, whereas percentage increases of 165.6 and 164.2 were recorded due to inoculation simultaeously with 50 Kg N fea"! as ammonium sulfate over that in case of the same N level as urea form. Regardless of treatment, cv. Sakha 69 supported higher soil dehy- drogenase activity compared to cv. Giza 163 whereas the mean activi- ties were 90.4 and 57.5 ug TPF g'', respectively. Also, cv. Sakha 69 supported higher nitrogenase activity compared to cv. Giza 163 giving an average increase of 114.9 nmoles Cohgh tg"? root. Plants inoculat- ed and received the rational dose (half the recommended dose) the of N fertilizer contained somewhat jower quantities of protein in their grains than those supplemented with the full N fertilization without inoculation. Incorporation into sail of biogas manure (2.5 ton ted" !) slightly stimulat- ed protein accumulation in grains. Application of 120 kg N fea! did magnify maize plant vigorousness with percentage increases of up to 213% in biomass production. Ahizobacterin supported ca. 230% higher plant N yield over N fertilization alone. Profuse ear yield of 3.44 ton fed" 1 was scored by urea form-full N supplied maize. Diazotroph inoculation in combination with 60 kg N fed"! revealed the superior dehydrogease activity in soil (124.1 yg TPF g°! soil). The maximum activity of 385 nmoles Cog tw! recorded in soil inoculated with rhizobacterin to- gether with 60 kg N fed'! as urea form represented a gain of 9.2 kg N feat Raising the N fertilization level decreased the N gain. As expect- ed, the lowest N budget was estimated for untreated soils.