Question

Matric Potential of which of the following is low :

• A. Dry soil
• B. Partially moist soil
• C. Moist soil
• D. Wet soil

Hint:

Remember that matric potential is a negative value representing tension. Since dry soil has the highest tension, its matric potential is the most negative (the lowest value).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Soil water potential is a measure of the energy state of water in the soil.
Matric potential ($\psi_m$) is a component of water potential that results from the adhesive forces between water and soil solids (capillary and adsorptive forces). It is always negative or zero.
Detailed Explanation:
Let us analyze the matric potential across different moisture levels:
- In saturated or wet soil, water is free and the matric potential is close to zero ($\psi_m \approx 0$).
- As soil dries out, water is held in smaller pores and as thin films on soil particles, increasing the tension. Since matric potential represents tension, it becomes more negative.
- In dry soil, the remaining water is held extremely tightly by solid particles under very high tension, resulting in a highly negative value (e.g., $-15\text{ bar}$ to $-31\text{ bar}$ or lower).
- In mathematics, a larger negative number is a "low" value (furthest from zero). Therefore, dry soil has the lowest matric potential.

Step 2: Final Answer:
The matric potential of dry soil is the lowest, which corresponds to Option (A).