In paddy field blue green algae are grown:-

Options

A. for medicinal use
B. To increase fertility of soil
C. To serve as food for fishes
D. To conserve water

Answer

**Step-by-Step Solution:**

1. **Understanding Blue-Green Algae**: Blue-green algae, also known as cyanobacteria, are photosynthetic microorganisms that can fix atmospheric nitrogen. This means they can convert nitrogen gas from the atmosphere into a form that plants can use.

2. **Role in Paddy Fields**: In paddy fields, blue-green algae grow on the surface of the soil. They are free-living organisms that thrive in wet conditions, making them well-suited for rice cultivation.

3. **Nitrogen Fixation**: One of the key benefits of blue-green algae is their ability to fix nitrogen. Nitrogen is an essential nutrient for plant growth, and its availability in the soil is crucial for the healthy development of rice plants.

4. **Enhancing Soil Fertility**: By fixing atmospheric nitrogen, blue-green algae enrich the soil with this vital nutrient, thereby increasing the fertility of the soil. This, in turn, supports better growth of rice crops.

5. **Natural Bio-fertilizer**: Blue-green algae act as a natural bio-fertilizer in paddy fields. They contribute to the overall health of the ecosystem and reduce the need for chemical fertilizers.

6. **Conclusion**: Given the options provided, the primary reason blue-green algae are grown in paddy fields is to increase the fertility of the soil.

**Final Answer**: The correct option is "to increase fertility of soil."

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