Question

The main sources of biofertilizers are
A. Rhizobium like bacteria
B. Cyanobacteria
C. Fungi
D. All of the above

Answer 1

Hint: Biofertilizers enrich the soil by increasing its nutrient quality.
These mostly contain microbes such as bacteria, blue-green algae, and some fungi species.

Complete answer: Biofertilizers are the type of fertilizers containing microbes that help enrich the soil by increasing nutrient quality.
1. These fertilizers promote the growth of plants and trees by increasing essential nutrient supply. The main sources of these fertilizers are various bacteria, blue-green algae (also called Cyanobacteria), and fungi.
2. Nitrogen-fixing bacteria are the most preferred ones.
3. The nitrogen-fixing bacteria also may be of the following types: symbiotic (Rhizobium), loose association bacteria (Azospirillum), free-living ones (Clostridium beijerinckii), etc.
4. Anabaena and Nostoc are important cyanobacteria.
5. They form an association with certain plants and are responsible for nitrogen fixation in them.
6. Fungi like Mycorrhiza serve as biofertilizers as they help absorbing phosphorus salts and also increase surface area for absorption.

So, the correct option is D. All of the above

Note: Biofertilizers are beneficial because prolonged use of general chemical fertilizers degrades soil quality but biofertilizers are environment friendly and also enhance the capacity of soil to hold water.
As the symbiotic relationship mentioned above provides benefits to both the organisms.