A field experiment was conducted on salt affected soil cultivated with cowpea crop (Vigna unguiculata)under drip irrigation system to evaluate the impact of using mineral fertilizer, fulvic acid, and seaweeds with or without bio-inoculation to combat soil salinity stress. All soil ameliorates were applied in combination with or without Aspergillus terreus inoculation. Seeds of cowpea plants were inoculated with Bradyrhizobium spp for all fertilization and amendment treatments. ¹⁵N isotope dilution technique was followed to accurately distinguish between N-derived sources gained by cowpea crop. Results indicated that shoot fresh weight of plants treated with full dose of mineral fertilizer was enhanced by fungal inoculation comparing to the un-inoculated plants. Similar trend, but to somewhat lower extent, was noticed with both root and seeds. Fresh weight of shoot, root and seeds of plants either inoculated or not were decreased, except shoot of un-inoculated one, when seaweeds were added as compared to those fertilized with mineral fertilizer. Similar trend, but to somewhat higher extent, was noticed with fulvic acid treatment. Contrary, seeds of plants were severely decreased in the presence of fulvic acid comparing to those treated with seaweeds or mineral N-fertilizer. The positive effect of fungal inoculation on enhancement of fresh weight was noticed with plants fertilized with mineral N-fertilizer. Nitrogen uptake by shoots of inoculated plants was higher in case of mineral fertilizer than those recorded with seaweeds but nearly similar to those induced by application of fulvic acid. In contrast, the un-inoculated plants didn't reflect any significant variation between the fertilization treatments. N uptake was increased with application of mineral fertilizer comparing to those resulted from application of seaweeds or fulvic acid. But the effect was not significant in fungal inoculated plants. N uptake by seeds of inoculated plants fertilized with full dose of mineral fertilizer was higher than those of plants treated with fulvic acid but nearly closed to those induced by addition of seaweeds. The highest values of nitrogen derived from fertilizer (Ndff) were recorded with application of mineral fertilizer. This holds true for all plant organs. Remarkable enhancement of Ndff was noticed in case of fungal inoculated plants comparing to the un-inoculated ones. Nitrogen derived from air (%Ndfa) ranged from 35% up to more than 60% depending on plant organ and fungal or non-fungal inoculation treatments. Ndfa were higher in un-inoculated plants than those recorded with the inoculated one. Seeds accumulate more Ndfa than roots or shoot.