Question

The permanent wilting point of soil corresponds approximately to which soil moisture tension?

• A. 0.33 bar
• B. 1 bar
• C. 10 bars
• D. 15 bars

Hint:

Remember: Field capacity is around 0.33 bar, while permanent wilting point is around 15 bars.

Answer 1

The Correct Option is D

Step 1: Understanding permanent wilting point.
The permanent wilting point (PWP) refers to the soil moisture condition at which plants can no longer extract sufficient water from the soil and remain permanently wilted even if placed in a humid environment. At this point, the water is held very tightly by soil particles.
Step 2: Understanding soil moisture tension.
Soil moisture tension represents the force with which water is held in the soil. As the soil becomes drier, the tension increases, making it more difficult for plant roots to absorb water.
Step 3: Relating PWP to soil moisture tension.
Scientifically, the permanent wilting point corresponds to a soil moisture tension of approximately 15 bars (or 1500 kPa). At this tension, plant roots cannot overcome the force holding water in the soil.
Step 4: Analyzing the options.
(A) 0.33 bar: This represents field capacity, not the wilting point.
(B) 1 bar: This value is too low and still allows plant water uptake.
(C) 10 bars: This is close but still below the permanent wilting threshold.
(D) 15 bars: Correct — this value accurately represents the permanent wilting point.
Step 5: Conclusion.
The permanent wilting point of soil corresponds approximately to a soil moisture tension of 15 bars.