Conversion of atmospheric free nitrogen to nitrates is called

Options

A. Nitration
B. Nitrogen fixation
C. Nitrification
D. Denitrification

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the conversion of atmospheric free nitrogen (N₂) into nitrates (NO₃⁻).

2. **Identifying the Process**: The conversion of atmospheric nitrogen into nitrates is part of a broader process known as nitrogen fixation. However, the specific conversion of nitrogen to nitrates is referred to as nitrification.

3. **Nitrogen Fixation**: Initially, atmospheric nitrogen is fixed by certain microbes into a usable form. This process involves converting N₂ into ammonia (NH₃) using an enzyme called nitrogenase.

4. **Nitrification Process**:
- The first step in nitrification is the conversion of ammonia (NH₃) into nitrites (NO₂⁻) by bacteria known as Nitrosomonas.
- The second step involves the conversion of nitrites (NO₂⁻) into nitrates (NO₃⁻) by another type of bacteria called Nitrobacter.

5. **Final Conclusion**: Therefore, the specific term for the conversion of atmospheric free nitrogen to nitrates is called **nitrification**.