Nitrogen fixing Cyanobacterial flora of Nadia District in West Bengal, India

Cyanobacteria play an important role in maintenance and build-up of soil fertility, consequently increase rice growth and yield as a natural bio fertilizer. The paddy field ecosystem provides a favourable environment for the growth of Cyanobacteria with respect to their requirement for light, water, temperature and nutrient availability. Continued three successive years (2011 -2014) studied the Occurrence of Cyanobacteria in rice growing fields of Nadia district in West Bengal, India. We survey and studied 3 different rice growing fields of Nadia district namely Haringhata, Kalayani and Jaguliya for studying the cyanobacterial diversity. These rice growing fields mainly comprises unicellular, non-heterocystous and heterocystous cyanobacteria. Total 37 species of Nitrogen fixing Cyanobacteria samples belonging to 21 genera and four orders i.e., Chroococcales, Oscillatoriales, Nostocales, and Stigonematales were isolated from various rice growing localities. Present investigations revealed that the pH range of soil was mostly acidic in Rabi season and it was more than Kharif crop season. Three major Cyanobacterial groups; Unicellular and colonial were slight more than Non-heterocystous i.e., 6 genera and 8 species. Non-heterocystous filamentous cyanobacteria were minimum and its 5 genera and 8 species and heterocystous filamentous cyanobacteria were maximum, its 10 genera and 19 species were occurrence in most of all low and upland rice growing areas.