An effort was made to Study the rice field cyanobacterial biodiversity and to screen them based on nitrogen fixing biofertilizer potential from 3 different subdivision viz –Tezpur, Biswanath chariali, Gahpur of sonitpur district of Assam(India). During the study period in both winter and summer altogether 115 no of soil samples were collected from paddy fields of low lying riverine belt of the river Brahmaputra. The distributional pattern showed that out of the 63 isolates 43 different BGA strains belonged to 15 genera.Among them the genera Nostoc, Anabaena, Aulososira Calothrix Wetiellopsis and Aphanocapsa were the dominant rice field BGA in the district. The highest amount of N2 content was recorded in Anabaena Spiroids (4.21%) and the lowest amount was recorded in the strain Aphanotheceae Nagelii (0.65%) overall and the mean amount of N2 content among all the genera was 2.57%. The present communication deals and concludes that the highly potential indigenous Cyanobacteria which are widely distributed can be exploited in the yield of rice cultivation in the district. Extension work is also utmost necessary to popularize the use of the indigenous Cyanobactaria as Bio-fertilizer.
