Response of sorghum (Sorghum bicolor) to inoculation with effective strain ol Azospirillum lipoferum. biogas manure and/or ammonium sulphate fertilization in the presence of either B. megatherium var. phosphaticum or Glomus mosseae was studied. Results show that counts of a amonifiers and nitrifiers were the highest in case of biogas manure + ammonium sulphate application at a rate of 50 kg N/fed. from each of them combined with mycorrhizal inoculation. Inoculation with Az. lipoferum in the presence of halt dose of inorganic N-fertilizer combined with VAM fungus increased the counts of Azospirilla. Mycorrhizal inoculation treatments gave higher values of total nitrogen. NH4-N, N03-N and CO2 evolution in soil than phosphate solubilizing bacteria treatments Inoculation with G. mosseae gave higher vaues of total and available phosphorus and total and soluble potassium in soil than inoculation with B. megatherium var. phosphaticum regardless the type of nitrogenous fertilization The treatments included mycorrhizal inoculation also gave higher values of plant height, leaves area/plant, fresh and dry weights of root and shoot system/plant than parallel treatments which included phosphate solubilizing bacteria. Azospirillum inoculum + ammonium sulphate (50 kg N/fed.) combined with Glomus mosseae gave the highest values of NPK and crude protein in shoot of sorghum plants. The treatments included G. mosseae gave higher values of chlorophyll pigments and carotenoids than parallel treatments which included phosphate solubilizing bacteria.