Use of symbiotic and free-living blue-green algae in rice culture

Floodwater and surface of flooded rice fields support photodependent N2-fixation by symbiotic and free-living blue-green algae. The article reviews the uses of Azolla in symbiosis with blue-green algae and free-living blue-green algae in wetland rice culture. There are many constraints on the wide use of either N_fixing systems by blue-green algae.