Question

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

• 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:

Avoid liming and ammoniacal fertilizer application together to prevent nitrogen loss via volatilization.

Answer 1

The Correct Option is A

Liming raises soil pH, leading to the conversion of ammonium to ammonia gas, which volatilizes, resulting in nutrient loss. Hence, liming and ammoniacal fertilizer application should be scheduled separately.

Answer 2

Reaction-based explanation: Liming materials such as \( \text{CaCO}_3 \) raise soil pH by neutralising acidity and releasing hydroxide ions.
In an ammoniacal fertiliser, nitrogen exists as the ammonium ion, \( \text{NH}_4^{+} \), which is in equilibrium with dissolved ammonia: \[ \text{NH}_4^{+} + \text{OH}^{-} \rightleftharpoons \text{NH}_3 + \text{H}_2\text{O} \]
Raising pH pushes this equilibrium to the right, converting more ammonium to gaseous ammonia, which readily escapes to the atmosphere, this volatilisation loss is exactly why liming and ammoniacal fertiliser applications are kept apart in field scheduling.
Since the reason describes the precise chemical pathway causing the assertion's outcome, both statements are true and R explains A.