What are biofertilizers? Give two examples.

(N/A) Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria,fungi,and cyanobacteria.
Examples:
$(i)$ $Rhizobium$,$Azospirillum$,and $Azotobacter$ are bacteria that fix atmospheric nitrogen in the soil.
$(ii)$ $Anabaena$,$Nostoc$,and $Oscillatoria$ (Blue-Green Algae) are used as biofertilizers to add organic matter and nitrogen to the soil.