Ashby’s Mannitol Agar is recommended for isolation of Azotobacter species from soil that can use mannitol and atmospheric nitrogen as source of carbon and nitrogen respectively. Azotobacter is a non-symbiotic nitrogen fixing bacteria, also known as biofertilizer. Dipotassium phosphate provides buffering to the medium. Various essential ions required for promoting growth of Azotobacter are also available in this medium.