Relative Nitrogen fixing efficiency of different isolates of Azotobacter species
Madan Kumar
The present study was conducted with a view to isolate, characterize and nitrogen fixing efficiency of fruit rhizospheric Azotobacterat Ranchi and Gumla districts of Jharkhand state. The isolates were evaluated for their ability to fix nitrogen in a culture medium. The nitrogen fixing efficiency was determined by using improved Kjeldahi method. Twelve isolates of Azotobacter were isolated from rhizosphere- Mango, Litchi, Pomegranate, Plantain, Jackfruit and lemon. Morphological features of the isolates of Azotobacterrevealed as long rods and Gram negative. The isolates were motile. Isolates of Azotobacter showed invariably pigments varying from light to dark brown in colour. The isolates belonging to the genus Azotobacter invariably exhibited positive response to catalyze but differed in their oxygen requirement. Growth of Azotobacter isolates on the upper surface of culture reflected their high efficiency for oxygen. One interesting features that emerged from the present investigation is that all fruit rhizosphoric isolates were found to be more nitrogen fixers in comparisons to other cereals and vegetables rhizosphere.
Key words: Azotobacter, Rhizosphere, Kjeldahi method, nitrogen fixing efficiency, Morphological features.