Abstract

A microaerophilic culture of Azotobacter chroococcum when introduced through seeds of rice varieties survived ard multiplied well in the rhizosphere throughout the crop growth under sterile and unsterile conditions. The rate of multiplication of A. chroo. coccum was more in the sterile soil then under unsterile soil. The colonization of Azotobacter in the rhizosphere was more pronounced during the boot-leaf and flowering stages than the initial stages. Although the varieties considerably differed in their abili ties to harbour Azotobacter in the root region, this inference does not bear any statis- tical significance. There was more nitrogen fixation in the rhizosphere soil than in the uncropped soil The study further revealed that in the water logged rice field soils. apart from Azotobacter several other photosynthetic microorganisms play a subtle role in nitrogen fixation.

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