Azolla is used as biofertilizer because it

Options

A. forms massive biomass
B. has association of nitrogen fixing Rhizobium
C. possesses association with nitrogen fixing cyanobacteria
D. has association with mycorrhiza

Answer

**Step-by-Step Solution:**

1. **Understanding Biofertilizers**:
- Biofertilizers are organisms that enhance the nutrient quality of the soil. They can be bacteria, fungi, or cyanobacteria (blue-green algae).

2. **Introduction to Azolla**:
- Azolla is a water fern that is recognized for its ability to improve soil fertility. It is specifically noted for its symbiotic relationship with nitrogen-fixing cyanobacteria.

3. **Role of Cyanobacteria**:
- The cyanobacteria associated with Azolla, particularly Anabaena azollae, play a crucial role in nitrogen fixation. This process converts atmospheric nitrogen into a form that plants can absorb and utilize, thus enriching the soil.

4. **Massive Biomass Production**:
- While Azolla does produce a significant amount of biomass, this characteristic alone does not define its role as a biofertilizer. The key aspect is its ability to fix nitrogen.

5. **Comparison with Other Options**:
- Other options mentioned, such as the association with rhizobium and mycorrhizae, are not applicable to Azolla. Rhizobium is typically associated with leguminous plants, and mycorrhizae involve a symbiotic relationship between fungi and plant roots, which is different from Azolla's function.

6. **Conclusion**:
- Therefore, Azolla is used as a biofertilizer primarily because of its association with nitrogen-fixing cyanobacteria, which enhances soil fertility and subsequently increases crop yield.

**Final Answer**: Azolla is used as a biofertilizer because it has a symbiotic relationship with nitrogen-fixing cyanobacteria (Anabaena azollae), which enriches the soil with nitrogen.

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