Subtopic: Soil water potentials and retention energy
Question Statement:
Soil water potential at permanent wilting point (PWP) in standard agricultural soils is approximately equal to: (Variation QB_PARAMETRIC_IDE_SWP_005)
Options:
(A) $-15\text{ bars} \; (-1.5\text{ MPa})$
(B) $-0.33\text{ bar} \; (-33\text{ kPa})$
(C) $-0.10\text{ bar} \; (-10\text{ kPa})$
(D) $-31\text{ bars} \; (-3.1\text{ MPa})$
Answer Key:
A
Step-by-Step Solution & Explanation
In classical soil physics:
- Field Capacity corresponds to matric suction between $-0.1$ to $-0.33\text{ bar}$ ($-10$ to $-33\text{ kPa}$).
- Permanent Wilting Point corresponds to a matric potential of $-15\text{ bars}$ ($-1.5\text{ MPa}$).
- Hygroscopic coefficient corresponds to approximately $-31\text{ bars}$.