Natural reservoir of phosphorus is in ...............

Explanation

**Step-by-Step Solution:**

1. **Understanding Phosphorus Cycling**:
- Phosphorus is an essential nutrient for living organisms and plays a crucial role in biological processes such as energy transfer and genetic material formation.

2. **Identifying the Type of Cycling**:
- The cycling of phosphorus is categorized as sedimentary. This means that the movement and transformation of phosphorus occur primarily through solid forms rather than gaseous or liquid phases.

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