Survival and Efficiency of N2-Fixing Cyanobacteria in Soil under Water Stress

Survival of five genera of N2-fixing cyanobacteria were studied under salt and drought stress in clay and sand soil. These conditions considerably decreased the survival of the tested organisms. Nitrogenase activity was also decreased and this could be attributed to the reduced of heterocyst frequency under the experimental conditions. Apparently, Nostoc microscopicum and Rivulara natans appeared to be water stress-tolerant species and remained for long period. There is a scope for selection of cyanobacterial species more tolerant to harsh conditions to prepare commercial inoculants for Agronomic practice.