Why are cyanobacteria considered useful in paddy fields ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Cyanobacteria:**
- Cyanobacteria are a group of photosynthetic bacteria that can perform photosynthesis and are known for their ability to fix atmospheric nitrogen.

2. **Role in Nitrogen Fixation:**
- These bacteria have the capability to convert atmospheric nitrogen (N₂) into ammonia (NH₃) through a process known as nitrogen fixation. This is crucial because nitrogen is an essential nutrient for plant growth.

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