Question

Which one of the following is regarded as a biofertilizer?

• A. An association between pteridophytes and cyanobacteria Anabaena
  
• B. An association between gymnosperms and Nostoc
  
• C. An association between legume and Rhizobium
  
• D. All of the above

Answer 1

The correct option is D All of the above

Cyanobacteria either free-living or symbiotic are considered as biofertilizer because they fix atmospheric nitrogen in term of nitrates and nitrites by a biological process like Rhizobium.

Blue-green algae belonging to a general Cyanobacteria genus, Nostoc or Anabaena fix atmospheric nitrogen and are used as inoculations for paddy crop grown both under upland and lowland conditions.

So, the correct answer is option D.