Bio-fertilizers are living organisms which help in increasing the fertility of

soil. It involves the selection of beneficial micro-organisms that help in

improving plant growth through the supply of plant nutrients. These are

introduced to seeds, roots, or soil to mobilize the availability of nutrients by

their biological activity. Thus, they are extremely beneficial in enriching the

soil with organic nutrients. Many species of bacteria and cyanobacteria have

the ability to fix free atmospheric nitrogen.

Rhizobium is a symbiotic bacteria found in the root nodules of leguminous

plants.

Azospirillium and Azotobocter are free living nitrogen-fixing bacteria,

whereas Anabena, Nostoc, and Oscillitoria are examples of nitrogen-fixing

cyanobacteria. Biofertilizers are cost effective and eco-friendly.