Question

Biofertilisers include

• A. All of the above
• B. Nitrogen fixing bacteria
  
• C. Nitrogen fixing cyanobacteria
  
• D. Mycorrhiza
  

Answer 1

The correct option is A All of the above

Introduction to biofertiliser
Biofertilisers consist of microorganisms that act to increase soil fertility. They are widely used in organic farming.

Role of nitrogen fixing bacteria as a biofertiliser
Nitrogen fixing bacteria have the ability to fix atmospheric nitrogen converting it to ammonia thus increasing the fertility of the soil. For example, $Azotobacter$, a free-living nitrogen-fixing bacteria, helps to increase the nitrogen content of the soil, thus enriching soil nutrients.

Role of mycorrhiza as biofertiliser
Mycorrhiza is an association of fungi with the roots of higher plants. This association helps in the solubilisation of phosphates for the plants, thus increasing soil fertility.

Role of cyanobacteria as biofertiliser
Cyanobacteria like $Anabaena$ and $Nostoc$ have been used as biofertilisers as they contain specialised cells called heterocysts that can fix atmospheric nitrogen.


Final answer
(D) All of the above