Question

The characteristics of saline-sodic soil are:

• A. pH \(< 8.5\), EC \(\ge 4 \text{ dS/m}\), SAR \(< 13\), ESP \(< 15\)
• B. pH \(\ge 8.5\), EC \(\ge 4 \text{ dS/m}\), SAR \(\ge 13\), ESP \(\ge 15\)
• C. pH \(< 8.5\), EC \(\ge 4 \text{ dS/m}\), SAR \(< 13\), ESP \(\ge 15\)
• D. pH \(< 8.5\), EC \(\ge 4 \text{ dS/m}\), SAR \(\ge 13\), ESP \(\ge 15\)

Hint:

Remember classification criteria

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Salt-affected soils are classified into saline, sodic (alkali), and saline-sodic based on electrical conductivity (EC), exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and pH.

Step 2: Detailed Explanation:
The United States Salinity Laboratory (USSL) defines these soils as follows:
1. Saline Soils: - \(\text{EC} \ge 4 \text{ dS/m}\) - \(\text{ESP} < 15\%\) (or \(\text{SAR} < 13\)) - \(\text{pH} < 8.5\) 2. Sodic (Alkali) Soils: - \(\text{EC} < 4 \text{ dS/m}\) - \(\text{ESP} \ge 15\%\) (or \(\text{SAR} \ge 13\)) - \(\text{pH} \ge 8.5\) (often up to \(10.0\)) 3. Saline-Sodic Soils: - \(\text{EC} \ge 4 \text{ dS/m}\) (due to excess soluble salts) - \(\text{ESP} \ge 15\%\) and \(\text{SAR} \ge 13\) (due to high exchangeable sodium) - \(\text{pH} < 8.5\) (because high soluble salts prevent extreme alkaline hydrolysis)

Step 3: Final Answer:
Saline-sodic soils are characterized by pH \(< 8.5\), EC \(\ge 4 \text{ dS/m}\), SAR \(\ge 13\), and ESP \(\ge 15\).