Azolla for Aquatic Nitrogen
From Appropedia
Azolla, a common little aquatic floating fern, is the host of a symbiotic blur-green algae, now more often called a cyanobacteria, which has the power to fix atmospheric nitrogen in a plant available form. Azolla is often cultivated in wetland rice paddies so that chemical fertilizers are not needed. See the link below.
The "Rice-Azolla-Fish" system-rice grown under the ridge culture in China, showing inter-rows being prepared for Azolla inoculation.
