2.2. Determination of nitrogenfixing capacity
Pure diazotrophic bacterial isolates were grown in 10 ml Ashby
broth in 20 ml test tube on a rotary shaker at 125 rpm under
continuous airflow at 301C for 72 h in triplicate. The uninoculated
media served as control. Afterward, the concentration of nitrogen
in each liquid culture was measured by digestion and subsequent
measurement by the Kjeldahl method (Bremner, 1965).