Role of Azotobacter paspali in Association with Paspalum notatum

Azotobacter paspali grows in the rhizospheres of Paspalum notatum where it is thought to fix nitrogen actively and hence improve pasture growth. In the experiments described here A. paspali improved growth primarily by producing growth regulating substances. Nitrogenase activity was not detected in rhizospheres of young plants. Its occurrence in older plants was not necessarily associated with the presence of A. paspali and was greater in the rhizopheres of control than of inoculated plants.