Azolla has enormous potential as a biofertilizer due to the large amount of nitrogen that it provides for all types of crops.
It is widely used in the Far East as a nitrogen biofertilizer in rice production – increasing rice yields by more than to 50% and the practice is also becoming common in Africa and South America.
Research into Azolla’s use in rice production has grown over the past years, with the International Rice Research Institute (IRRI) developing more than 500 Azolla hybrids for use in different climates and habitats.
Although nitrogen is abundant in the earth’s atmosphere, few plants are able to assimilate nitrogen directly from the atmosphere and most plants obtain their nitrogen from complex compounds in the soil. Fertilizes add these to the soil and may be organic (composed of organic matter) or inorganic (made of simple, inorganic chemicals or minerals).
Inorganic nitrogen fertilizers are mostly synthesized by the Haber-Bosch Process and the high yields achieved by modern agriculture are only possible because of the worldwide use of inorganic nitrogen fertilizers. Almost 100 million tons of nitrogen fertilizer per year are now needed every year to maintain this output – more than ten times the amount used in 1961.
Chemical fertilizers also have numerous detrimental effects on the Earth System and they are becoming increasingly expensive.
Biofertilizers provide an alternative that improves the soil in many ways that are not provided by chemical fertilizers and they do not have their negative side effects.
They organic including living microorganisms matter to the soil. These produce gums, waxes, and resins that are resistant to decomposition, helping to help bind together soil particles as granules or aggregates.
Legumes, which are characterized by having seeds inside a pod or ‘legume’, are the mostly commonly used biofertilizers, or summer ‘green manures’.
Like Azolla, they contain symbiotic cyanobacteria that provide some of their nitrogen directly from the atmosphere, but unlike Azolla, their relationship with cyanobacteria needs to be renewed each generation.
Azolla’s cyanobacteria are directly transmitted to the next generation during the plant’s reproductive cycle so that the two organisms have co-evolved together for millions of years, resulting in Azolla’s high level of efficiency in transferring atmospheric nitrogen into a biofertilizer – providing almost three times more nitrogen to the soil than legumes.
Typical rates for legumes are 400 kg of nitrogen per hectare per year those for Azolla are 1100 kg of nitrogen per hectare per year.