Question

Let \( \psi \) represent soil suction head and \( K \) represent hydraulic conductivity of the soil. If the soil moisture content \( \theta \) increases, which one of the following statements is TRUE?

• A. \( \psi \) decreases and \( K \) increases.
• B. \( \psi \) increases and \( K \) decreases.
• C. Both \( \psi \) and \( K \) decrease.
• D. Both \( \psi \) and \( K \) increase.

Hint:

Soil suction head decreases with increasing moisture content, while hydraulic conductivity increases because water moves more easily through wetter soils.

Answer 1

The Correct Option is A

Soil suction head (\( \psi \)) is inversely related to the soil moisture content (\( \theta \)). As the moisture content increases, the suction head decreases. Hydraulic conductivity (\( K \)) is positively related to the moisture content, meaning that as the moisture content increases, the hydraulic conductivity also increases.

Step 1: Understand the relationship between \( \psi \) and \( \theta \).
As soil moisture increases, the suction head \( \psi \) decreases because less suction is required to pull water into the soil.

Step 2: Analyze the relationship between \( K \) and \( \theta \).
Hydraulic conductivity increases as moisture content increases because wetter soils allow for easier water movement.

Final Answer: (A) \( \psi \) decreases and \( K \) increases.