Q. Consider the following:

1. Rhizobium
2. Azotobacter
3. Mycorrhiza
4. Azolla

Which of the above are classified as biofertilizers?
Answer: 1, 2, 3 and 4
Notes: All the listed organisms—Rhizobium, Azotobacter, Mycorrhiza, and Azolla—are recognized as biofertilizers in India. They contribute to soil fertility by fixing atmospheric nitrogen or enhancing nutrient uptake. Azolla acts as a companion crop in paddy fields and supports nitrogen fixation, while mycorrhiza enhances water and mineral absorption for plants by forming symbiotic associations with roots.