Question

Given below are two statements:
Statement (I): Sulphur is the major problem in sodic soils.
Statement (II): They have an ESP \(>15\), the \(EC_e\) is \(<4\) dS \(m^{-1}\), and the lower limit of the saturation extract SAR is 13.
In light of the above statements, choose the most appropriate answer from the options given below.

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

Hint:

To remember salt-affected soil classification:
- Saline: \(\text{EC} > 4\), \(\text{ESP} < 15\), \(\text{SAR} < 13\), \(\text{pH} < 8.5\).
- Sodic: \(\text{EC} < 4\), \(\text{ESP} > 15\), \(\text{SAR} \ge 13\), \(\text{pH} > 8.5\).
- Saline-Sodic: \(\text{EC} > 4\), \(\text{ESP} > 15\), \(\text{SAR} \ge 13\), \(\text{pH} \approx 8.5\).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Sodic (alkali) soils are salt-affected soils characterized by an excess of exchangeable sodium ions (\(\text{Na}^+\)) on the soil colloid exchange complex, leading to poor physical structure and high pH.

Step 2: Detailed Explanation:
Let us analyze both statements systematically:
- Statement (I):
The major problem in sodic soils is the excess of exchangeable sodium (\(\text{Na}^+\)), which causes clay dispersion, clogs soil pores, and elevates pH (> 8.5).
Sulphur is not a problem in these soils; in fact, elemental sulphur or gypsum (calcium sulphate, \(\text{CaSO}_4 \cdot 2\text{H}_2\text{O}\)) is added as an amendment to reclaim sodic soils by supplying calcium to displace exchangeable sodium.
Therefore, Statement (I) is incorrect.
- Statement (II):
According to the diagnostic criteria established by the United States Salinity Laboratory (USSL), sodic soils are characterized by:
1. Exchangeable Sodium Percentage (ESP) \(>\) 15%.
2. Electrical conductivity of the saturation extract (\(\text{EC}_e\)) \(<\) 4 dS \(\text{m}^{-1}\).
3. Sodium Adsorption Ratio (SAR) of the saturation extract \(\ge\) 13.
Therefore, Statement (II) is correct.
Thus, Statement (I) is incorrect but Statement (II) is correct.

Step 3: Final Answer:
The correct option is (D), as Statement (I) is incorrect and Statement (II) is correct.