Effect of blue-green algae on soil nitrogen

Nitrogen fixed by cyanobacteria is released either through exudation or through microbial decomposition after the alga dies. In paddy fields, the death of algal biomass is most frequently associated with soil dessication at the end of the cultivation cycle and algal growth has frequently resulted in a gradual build up of soil fertility with a residual effect on succeeding crop also. The effect of blue-green algae (BGA) on soil nitrogen was carried out from June to December 2005. The BGA inoculum ( Nostoc , Anabaena , Westiellopsis , Aulosira and Scytonema ) was used after rice transplantation. After rice harvest, the soil nitrogen was then estimated. The experiment revealed that the N content of the soil with BGA inoculated treatments was comparatively higher than other treatments used in the experiment in which the soil nitrogen was found to be 0.25%. Keywords: Blue-green algae (BGA), inoculum, soil nitrogen