Question

Assertion (A): Gypsum is commonly used for the reclamation of sodic soil.
Reason (R): Reclamation process involves reduction in exchangeable sodium with calcium and its removal from soil solution through leaching.

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

Hint:

Gypsum helps reclaim sodic soils by replacing sodium with calcium, which is then leached out.

Answer 1

The Correct Option is A

Gypsum provides calcium, which replaces sodium ions in sodic soils. The displaced sodium is leached away through proper drainage, improving soil structure. Hence, both A and R are true and R explains A correctly.

Answer 2

Verifying through the ion-exchange reaction: Gypsum (calcium sulphate) dissolves in soil water to release Ca²⁺ ions.
These Ca²⁺ ions displace Na⁺ held on the soil's exchange complex, written as: Na₂-Soil + Ca²⁺ → Ca-Soil + 2Na⁺.
The released Na⁺, now in the soil solution rather than on exchange sites, is removed by leaching with adequate drainage, lowering the exchangeable sodium percentage.
This matches exactly what Reason (R) describes, and it is the mechanism that makes Assertion (A) true, so (R) correctly explains (A).