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

This phenomenon is known as hysteresis in soil moisture. It occurs due to differences in contact angle during wetting and drying. During imbibition (wetting), a greater contact angle reduces water retention at same matric potential, validating the assertion and its reason.