Question

Assertion (A): Equilibrium water content in soil at a certain matric potential is higher when the soil is under the drying process (desorption) compared to when the soil is under the wetting process (sorption).
Reason (R): The contact angle between water and the soil solid phase is greater during the imbibition of water than during drainage.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

Hysteresis causes moisture content at same potential to differ between drying and wetting paths.

Answer 1

The Correct Option is A

Step 1: Irregular soil pore necks make water retention differ between wetting and drying.
Step 2: During drying, more water stays trapped at a given suction than during wetting.
Step 3: This happens because the contact angle is larger while wetting than while draining.
Step 4: Both (A) and (R) are correct and (R) explains (A), so option 1 is the answer.