RESUMEN
Four heterocystous cyanobacteria, isolated from grasslands of Ujjain were selected to prepare the clay based inoculants. Inoculants were evaluated for shelf life in terms of the titer value at 6 month intervals for 24 months. For colonization by inoculants in natural grasslands, the clay based inocula were applied to the field at: 40, 80 and 120 kg/ha and their survival was estimated at different time interval. Fuller's earth based inoculants had showed 50-65% survival after two year storage. After showing an initial decline, the population of the inoculated cyanobacteria became stable after 3 months. The inoculated strains persisted in the soil for longer duration, even after four months, their population was about 10-70 times higher than that of the uninoculated plots.