Cyanobacteria as N-source fertilizer?
The organisms, called cyanobacteria, are unique in their ability to absorb and immobilize excess nitrogen in soils that are too rich and also to "fix" or add carbon and nitrogen from the air to soils that are depleted, according to Mary Ann Bruns, associate professor of ecosystem science and management in Penn State's College of Agricultural Sciences.
Cyanobacteria occur naturally at times in some soils. If they can be cultivated and more widely introduced, they could substitute for some of the fertilizer now being applied by farmers, Bruns explained.
Colonies of cyanobacteria create a bluish-green biofilm over soil, most often in the fall after crops are harvested. Bruns became aware of their existence when she noticed a colony a decade or so ago at the Penn State Agronomy Research Farm at Rock Springs. Now, after several years of research, she estimates that their nitrogen-fixing abilities could substitute for up to 25 pounds per acre of manufactured nitrogen fertilizer.
"But best of all, cyanobacteria and their associated mosses and algae can take up excess nitrogen, keep it from being lost through runoff or leaching, and release it more slowly during the growing season. These biofilms also serve to make the soil surface more cohesive and resistant to erosion, and they will not fix nitrogen from the air if there already is nitrogen in the soil," Bruns said.