Phosphorus fertilization and the growth and N₂-fixation of Azolla and blue-green algae in rice field

Application of 1% aqueous solution of single super phosphate increased the growth and N₂-fixation of both Azolla and Blue-green algae (BGA) biofertilizers. Phosphorus alone did not increase the rice yield while Azolla and BGA inoculated along with phosphorus increased the grain and straw yield significantly. The yield of rice obtained by Azolla and 30 kg N ha^-1 as urea were similar but BGA showed comparatively lesser response.