Question

Which of the following is not a biofertilizer?

• A. Azolla - Anabaena symbiosis
• B. Mycorrhiza
• C. Legume-Rhizobium symbiosis
• D. Algae-fungi symbiosis

Answer 1

The correct option is D Algae-fungi symbiosis

A biofertilizer is a living microorganism or made up of dried microorganisms. It is applied to plant surfaces, or soil colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Biofertilizers such as Rhizobium, Azotobacter, Azospirilium, mycorrhiza and blue-green algae have been in use for a long time.

• Rhizobium inoculant is used for leguminous crops. Azotobacter can be used with crops like wheat, maize, mustard, cotton, potato, and other vegetable crops.
• Blue-green algae belonging to a general Cyanobacteria genus fix atmospheric nitrogen and are used as inoculations for paddy crop grown both under upland and lowland conditions.
• Mycorrhiza is a symbiotic association between a fungus and a plant. The Mycorrhiza plays a key role in selective absorption of immobile (P, Zn, and Cu) and mobile (S, Ca, K, Fe, Mn, Cl, Br, and N) elements to plants. These are available to plants in less amount.
• Anabaena in association with water fern Azolla contributes nitrogen up to 60 kg/ha/season and also enriches soils with organic matter.
• Algae-fungi symbiosis is not used as biofertilizer because their symbiotic association forms lichens.

So, the correct answer is option D.