Biofertilizers are low cost, renewable sources of plant nutrients which supplement chemical fertilizers. These are nothing but selected strains of beneficial soil microorganisms cultured in the laboratory and packed in a suitable carrier. They can be used either for seed treatment or soil application.

Types of Biofertilizers
The following types of biofertilizers are available to the farmers in India.
• Nitrogen fixing biofertilizers
eg. Rhizobium, Bradyrhizobium, Azospirillum and Azotobacter.
• Phosphorous solubilising biofertilizers (PSB)
eg. Bacillus,Pseudomonas and Aspergillus
• Phosphate mobilizing biofertilizer
eg. Mycorrhiza
• Plant growth promoting biofertilizers
eg. Pseudomonas sp

How biofertilizers work?
• Biofertilizers fix atmospheric nitrogen in the soil and root nodules of legume crops and make it available to the plant.
• They solubilise the insoluble forms of phosphates like tricalcium, iron and aluminium phosphates into available forms.
• They scavenge phosphate from soil layers.
• They produce hormones and anti metabolites which promote root growth.
• They decompose organic matter and help in mineralization in soil.
• When applied to seed or soil, biofertilizers increase the availability of nutrients and improve the yield by 10 to 25% without adversely affecting the soil and environment