Deep black soil is productive due to high proportion of

Options

A. sand and zinc
B. gravel and calcium
C. clay and humus
D. silt and earthworm

Explanation

**Step-by-Step Solution:**

1. **Understanding Deep Black Soil**: Deep black soil, also known as Regur soil, is characterized by its dark color and is typically found in regions with a specific climate and vegetation.

2. **Components of Deep Black Soil**: The productivity of deep black soil is mainly attributed to its high content of clay and organic matter, particularly humus.

3. **Role of Humus**: Humus is formed from the decomposition of organic matter, such as dead plants and animals. It is rich in nutrients and plays a crucial role in enhancing soil fertility.

4. **Nutrient Reservoir**: The presence of humus in deep black soil makes it a reservoir of nutrients, which are essential for plant growth. This nutrient-rich environment supports agriculture and contributes to the soil's productivity.

5. **Comparison with Other Soil Types**: Other soil components like sand and gravel do not contribute to the productivity of deep black soil. Sand has low moisture retention and high percolation, while gravel contains coarse particles with less mineral content.

6. **Conclusion**: Therefore, the high proportion of humus in deep black soil is what makes it productive, confirming that the correct answer to the question is the high proportion of humus.

**Final Answer**: The deep black soil is productive due to a high proportion of humus.

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