ABSTRACT The study's purpose was to identify and isolate a salinity-tolerant Azotobacter chroococcum strain that would be used as a biofertilizer. Different salinity-affected sites in North Sinai,  Ras Sudr and Sahle El-Tina, were sampled for soil. Under saline conditions, two extremely effective halotolerant Azotobacters were tested for their nitrogen fixing, phosphate dissolving, and synthesis of indol, gibrillin, and siderophores at (3 % NaCl). A field experiment in Sahle El-Tina, North Sinai, looked at the effects of biofertilization and Ditoms foliar spray on the development and production of sunflower cultivar Sakha 53. Sunflower yield, oil content, and chemical content were increased significantly when biofertilizer and diatoms interacted. Also, the interaction between diatom foliar spray and biofertilization treatments had a significant impact on all yield and yield components. In addition, total microbial counts, CO₂ evolution, and azotobacter counts in the rhizosphere soil indicated significant microbial activity, and enzymatic activity (Dehydrogenase) revealed a good response in all treatments compared to the uninoculated control.