Blue-green algae (cyanobacteria) can play an important role in fixing atmospheric nitrogen and it supplies plants with nitrogen they need in the soil. The blue-green algae were selected as a biofertilizer for the wheat plant. A pot experiment was carried out at the Agriculture Faculty, Al-Azhar University, Cairo, Egypt, in 2021 to investigate the growth and yield of wheat by using cyanobacteria strains with two types of soil. These cyanobacteria strains were isolated and identified as Nostoc lichenoides, Nostoc indistinguendun and Nostoc favosum and their inoculants were added individually and in a mixture. Sandy and clay loam soil textures were used, using four inorganic nitrogen levels (0, 20, 40 and 60 % N) was used from recommended dose (70 kg N fed -1 ). Generally, data introduced that the highest significant increase in plant height, spikes number, spikes dry weight, grains weight and 1000-grain weight with 40 to 60% levels inorganic nitrogen when used in clay loam soil and mixture from cyanobacterial inoculants treatment. From these results, the blue-green algae have reduced the use of chemical fertilizers for nitrogen application from 40 to 60% compared with recommended doses of nitrogen.

Applicability of cyanobacteria strains (Nostoc lichenoides, Nostoc indistinguendun, Nostoc favosum) and their mixture for effect on microbial communities of soil under four levels of inorganic nitrogen (0, 20, 40 and 60% N) was used with recommended doses of nitrogen (70 kg N fed -1 ). This experiment was carried out in two types of soil texture (sandy and clay loam) to enumerate the number of viable bacteria, azotobacter, actinomycetes, and fungi. Results indicated that the cyanobacterial strains varied significantly and pronounced an increase in all microbes. So, the sandy soil count was lower than clay loam soil. The treatment with Nostoc favosum recorded the highest total counts of bacteria (270.9 ×10 6 CFU/g dry soil) compared to those found by the other strains of tested cyanobacteria. The addition of cyanobacteria to the sandy soil increased the number of Azotobacter, and the best number of azotobacter in the mixture was (52.3×10 3 CFU/g dry soil) compared to uninoculated (20.5×10 3 CFU/g dry soil). However, inoculating two soil types with the mixture of cyanobacterial strains gave the highest Actinomycetes counts compared with individual strain. Also, the treatment of types soil with the mixture of cyanobacterial strains gave the highest counts of fungi compared with any other inoculated. The inoculation with other cyanobacteria strains and their mixture increased the soil microbial population including, total counts of bacteria, Azotobacter, Actinomycetes, and fungi.

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