Biofertilizers are micro-organims which bring about nutrient enrichment of soil by enhancing their availability
(i)
Manures- They are semi-decayed organic remains of various types -
farmyard manure, green manure, compost and vermicompost. As the manure
decay further takes place they release minerals locked in them.
(ii)
Nitrogen Fixing Organisms- They are certain bacteria and cyanobacteria
which are capable of converting gaseous nitrogen into salts of nitrogen.
(iii) Mycorrhiza- It
is an association between a fungus and roots of plants. Mycorrhiza is
able to pick up inorganic nutrients from organic matter.