The kind of soil water most useful to plant is

Options

A. Hygroscopic water
B. Gravitational water
C. Capillary water
D. None of above.

Answer

**Step-by-Step Solution:**

1. **Understanding Soil Water Types**:
- There are different types of soil water that plants interact with, including hygroscopic water, gravitational water, and capillary water.

2. **Defining Hygroscopic Water**:
- Hygroscopic water is the water that is absorbed from the atmosphere and is held tightly by soil particles. This water forms a thin film around the soil grains and is not available to plants because it is too tightly bound to the soil.

3. **Defining Gravitational Water**:
- Gravitational water is the water that moves through the soil due to the force of gravity. This type of water percolates downwards and can reach the water table. It is also not available to plants as it drains away quickly.

4. **Defining Capillary Water**:
- Capillary water is the water that is retained in the small spaces between soil particles. It forms thin films around the particles and is held by surface tension. This water is available to plants and is essential for their growth.

5. **Identifying the Most Useful Soil Water**:
- Among the three types of soil water, capillary water is the most useful to plants because it is readily available for uptake by plant roots.

6. **Conclusion**:
- Therefore, the correct answer to the question is capillary water.

**Final Answer**: Capillary water is the kind of soil water most useful to plants.

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