Why Nitrogen is not considered a true mineral?

Explanation

### Step-by-Step Solution:

1. **Definition of True Minerals**: True minerals are inorganic substances that are essential for plant growth and are typically absorbed directly from the soil in their mineral form.

2. **Nature of Nitrogen**: Nitrogen is a gas that constitutes a significant portion of the Earth's atmosphere (approximately 78%). However, in its gaseous form (N₂), it is inert and not directly usable by plants.

3. **Absorption by Plants**: Plants cannot absorb nitrogen directly from the atmosphere. Instead, they take up nitrogen in the form of nitrates (NO₃⁻) or ammonium (NH₄⁺) from the soil.

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