Question

Which of the following is a non-symbiotic biofertilizer?

• A. VAM
• B. Azotobacter
• C. Anabaena
• D. Rhizobium

Answer 1

The correct option is B

Azotobacter

The correct option is B.

The explanation for the correct option:

1. Azotobacter is a non-symbiotic, free-living nitrogen-fixing bacteria.
2. They are aerobic and free-living soil microbes, which perform an essential function in the nitrogen cycle.
3. They convert atmospheric nitrogen to ammonia, which is further utilized by plants.

The explanation for the incorrect options:

Option A:

1. VAM or vesicular-arbuscular mycorrhiza is produced due to the symbiotic association between some phycomycetous fungi and angiosperm roots.
2. VAM performs an essential function in improving the soil nutrient dynamics and chemical, physical, and biological properties of the soil.

Option C.

1. Anabaena is nitrogen-fixing cyanobacteria, which prevail as plankton.
2. The blue-green algae Anabaena and Azolla produce a symbiotic association.
3. The fern, that is, Azolla provides a habitat for Anabaena, and Anabaena provides nitrogen to Azolla.

Option D:

1. Rhizobium refers to Gram-negative soil bacteria, which fix nitrogen.
2. Legumes form a symbiotic association with nitrogen-fixing bacteria, that is, rhizobia.
3. The outcome of the symbiosis is the formation of nodules on the roots of the plant, within which the bacteria can transform atmospheric nitrogen into ammonia, which can be utilized by the plant.

Final answer: Azotobacter is a non-symbiotic fertilizer.