Question

The fertilizer having least equivalent acidity is:

• A. Urea
• B. Ammonium nitrate
• C. Ammonium chloride
• D. Calcium ammonium nitrate

Hint:

Equivalent acidity values for nitrogenous fertilizers:
- Ammonium chloride = 128 (highly acidifying)
- Urea = 80--84
- Ammonium nitrate = 60
- Calcium Ammonium Nitrate (CAN) = 0 (neutral fertilizer, also known as 'Kisan Khad').

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Ammonium-based nitrogenous fertilizers can acidify the soil over time.
This occurs because the nitrification of ammonium releases hydrogen ions (\(H^+\)) into the soil solution.
Equivalent acidity is defined as the amount of calcium carbonate (\(CaCO_3\)) required to neutralize the acid residue produced by applying \(100\text{ kg}\) of an nitrogenous fertilizer in the soil.

Step 2: Detailed Explanation:
Let us compare the equivalent acidity values of the listed fertilizers:
- Ammonium chloride: This is a highly acidifying fertilizer with an equivalent acidity of approximately \(128\text{ kg }CaCO_3\) per \(100\text{ kg}\) of fertilizer.
- Urea: Has an equivalent acidity of approximately \(80\text{ to }84\text{ kg }CaCO_3\) per \(100\text{ kg}\) of fertilizer.
- Ammonium nitrate: Has an equivalent acidity of approximately \(60\text{ kg }CaCO_3\) per \(100\text{ kg}\) of fertilizer.
- Calcium Ammonium Nitrate (CAN): This fertilizer is manufactured by mixing ammonium nitrate with limestone or calcium carbonate, which acts as a built-in neutralizing agent.
Because of this calcium carbonate content, CAN is practically a neutral fertilizer with an equivalent acidity of zero (or extremely close to zero, typically \(0\text{ to }10\)).
Therefore, among the given options, Calcium Ammonium Nitrate has the least equivalent acidity.

Step 2: Final Answer:
The fertilizer having the least equivalent acidity is calcium ammonium nitrate.