Question

Given below are two statements:
Statement (I): Single superphosphate, double superphosphate, triple superphosphate are mono-calcium phosphate.
Statement (II): Mono calcium phosphates are water soluble and thus have high leaching losses.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

Remember that phosphorus is the most immobile macronutrient in the soil profile. Leaching of phosphorus is extremely negligible compared to nitrogen.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Phosphate fertilizers differ in water solubility and soil reactions. Unlike nitrate ions, soluble orthophosphates react rapidly with soil components and become immobilized.

Step 2: Detailed Explanation:
- Statement (I) is true: Single Superphosphate ($\text{SSP}$), Double Superphosphate ($\text{DSP}$), and Triple Superphosphate ($\text{TSP}$) contain active phosphorus in the highly water-soluble form of monocalcium phosphate monohydrate [$\text{Ca}(\text{H}_2\text{PO}_4)_2 \cdot \text{H}_2\text{O}$].
- Statement (II) is false: Monocalcium phosphate is water-soluble, but it does not suffer from high leaching losses in the soil. When added to soil, the phosphate ions ($\text{H}_2\text{PO}_4^-$) react rapidly with iron and aluminum oxides in acid soils, or calcium carbonate in alkaline soils. This reaction precipitates them into insoluble forms (adsorption and fixation), making phosphorus highly immobile in the soil profile.
Thus, Statement (I) is true but Statement (II) is false.

Step 3: Final Answer:
The combination matches Option (C).