Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A) : Liming should not be done along with ammoniacal fertilizer applicaton.
Reason (R) : Liming leads to volatilisation loss of ammonia.

In light of the above statements, choose the correct answer from the options given below.

• 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:

To minimize volatilization losses, apply lime several weeks before applying nitrogen fertilizers to allow the lime to fully react with the soil complex.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Chemical reactions between soil amendments and fertilizers can alter nutrient availability and cause substantial nutrient losses.

Step 2: Detailed Explanation:
Assertion (A) is correct because co-applying agricultural lime (calcium carbonate/hydroxide) and ammoniacal fertilizers (e.g., ammonium sulfate or ammonium chloride) must be avoided.
Reason (R) is correct because lime acts as an alkaline agent that raises the soil pH.
In an alkaline environment, ammonium ions (\(\text{NH}_4^+\)) react with hydroxyl groups (\(\text{OH}^-\)) to form unstable ammonium hydroxide, which dissociates to release free ammonia gas (\(\text{NH}_3\)):
\[ \text{NH}_4^+ + \text{OH}^- \rightarrow \text{NH}_3\uparrow + \text{H}_2\text{O} \]
This ammonia gas volatilizes and escapes into the atmosphere, resulting in severe nitrogen loss.
Therefore, (R) directly explains the chemical basis for the warning in (A).

Step 3: Final Answer:
Both (A) and (R) are true, and (R) is the correct explanation of (A).