Question

Given below are two statements, one is labelled as Statement (1) and other one labelled as Statement (2).
Statement (1): Sandy soils heat up faster than clay soils because of lower heat capacity of clay soils.
Statement (2): Gypsum requirement of sandy soils is higher as compared to clay soils.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statements are correct.
• B. Statement (1) is correct but Statement (2) is incorrect.
• C. Statement (1) is incorrect but Statement (2) is correct.
• D. Both Statements are incorrect.

Hint:

Remember that water governs both the thermal and chemical properties of soils.
High water retention in clay leads to high heat capacity (warms up slowly).
High surface area of clay leads to high CEC (higher amendment requirements).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This question requires an understanding of basic soil physics and soil chemistry properties.
Specifically, it tests the relationship between soil texture, water content, thermal properties (heat capacity), and chemical reclamation requirements (cation exchange capacity and gypsum requirement).

Step 3: Detailed Explanation:
Let us analyze each statement individually:
- Statement (1): Sandy soils indeed heat up faster than clay soils.
However, the reason provided in the statement is incorrect.
Clay soils hold more water because of their fine texture and high pore space.
Since water has a very high specific heat capacity (\(184\text{ J/g}^\circ\text{C}\)), soils with higher moisture content require more heat energy to raise their temperature.
Therefore, clay soils have a higher heat capacity than sandy soils, not lower.
Sandy soils have low water retention, so their heat capacity is lower, making them warm up faster.
Thus, Statement (1) contains an incorrect scientific justification.
- Statement (2): The gypsum requirement (\(\text{CaSO}_4 \cdot 2\text{H}_2\text{O}\)) is used to reclaim sodic (alkali) soils.
Gypsum requirement depends directly on the soil's Cation Exchange Capacity (CEC) and the amount of exchangeable sodium to be replaced.
Clay soils contain fine clay minerals with very high surface area and negative charge, giving them a significantly higher CEC compared to coarse-textured sandy soils.
Therefore, a sodic clay soil has many more exchangeable sodium ions that need replacement by calcium than a sodic sandy soil.
Consequently, the gypsum requirement of clay soils is much higher than that of sandy soils.
Thus, Statement (2) is incorrect.

Step 4: Final Answer:
Since both Statement (1) and Statement (2) are incorrect, the correct choice is Option (D).