Azotobacters and azospirilla are now in extensive use in the form of carrierbased cultures in tropical regions of India.
A. chroococcum M4 (an isolate from maize rhizosphere) is usually recommended for treatment of maize.
In our study, best results were, however, obtained with A. chroococcum W5 (an isolate from wheat rhizosphere).
Since wheat is a winter crop in tropical India, this strain is perhaps more adapted to relatively lower temperatures. This strain gave the best plant growth and yield response at an elevation of 1200 m amsl in summer, and also established higher populations in the rhizosphere than the other bacterial strains (Fig. 1(d)).