Why is Nostoc used as a biofertiliser?

Answer

**Step-by-Step Solution:**

1. **Identify Nostoc**: Nostoc is a type of cyanobacteria, which are photosynthetic microorganisms that can be found in various environments, including soil and water.

2. **Nitrogen Fixation**: One of the key features of Nostoc is its ability to fix atmospheric nitrogen. This means it can convert nitrogen gas (N₂) from the atmosphere into ammonia (NH₃), which is a form of nitrogen that plants can utilize.

3. **Free Living and Photosynthetic**: Nostoc is a free-living organism, meaning it does not require a host to survive. Additionally, it is photosynthetic, allowing it to produce its own food using sunlight, which contributes to its sustainability as a biofertilizer.

4. **Adding Organic Matter**: By fixing nitrogen, Nostoc contributes to the nutrient content of the soil. It also adds organic matter, which improves soil structure, enhances moisture retention, and promotes the growth of beneficial microorganisms.

5. **Conclusion**: Due to its ability to fix nitrogen and enhance soil quality by adding organic matter, Nostoc is effectively used as a biofertilizer in agricultural practices. This helps in improving crop yields and reducing the need for synthetic fertilizers.

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