Biofertilizers are micro-organisms which bring about nutrient enrichment of soil by enhancing the availability of nutrients to crops. The micro-organisms which act as Bio-feretilizers are bacteria, cyano bacteria and mycorrhizal fungi. bacteria and cyanobacteria have the property of Nitrogen fixation while mycorrhizal fungi withdraw minerals from organic matter for the plant with which they are associated.

Rhizobium fix atmospheric nitrogen into organic forms through nodules on the roots of leguminous plants, which is used by plant as nutrient. Fungi are also known to form symbiotic associations with plants (i.e. mycorrhiza)

Cyanobacteria are auto trophic microbes widely distributed in aquatic and terresterial environments, many of which can fix atmospheric nitrogen, e.g., Anabana, Nostoc etc.

Biofertilizers are Biological in nature and so are biodegradable. They do not spoil the quality of the soil. It supplies organic matter and additional nitrogen like Rhizobiom, Azotobactor etc.