Question

The yield of many crops is restricted at what range of electrical conductivity of the saturation extract of a soil :

• A. 2-4 dS/m
• B. 4-8 dS/m
• C. 8-16 dS/m
• D. > 16 dS/m

Hint:

The threshold salinity level (\(\text{EC}_e\)) at which yield starts to decline is crop-specific.
For sensitive crops like beans, the threshold is about 1.0 dS/m, whereas for highly tolerant crops like barley, it is about 8.0 dS/m.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Soil salinity is measured by the electrical conductivity of the saturation extract (\(\text{EC}_e\)), expressed in decisiemens per meter (dS/m).
High concentrations of soluble salts in the soil solution increase osmotic pressure, making it difficult for plant roots to absorb water and essential nutrients, which restricts crop growth and yield.

Step 2: Detailed Explanation:
The United States Salinity Laboratory (USSL) classifies soils into different salinity classes based on \(\text{EC}_e\) values and their corresponding effects on crop growth:
- 0 to 2 dS/m (Non-saline): Salinity effects are mostly negligible; only extremely sensitive plants might show restricted growth.
- 2 to 4 dS/m (Slightly saline): The yields of very sensitive crops (such as peach, pear, and some beans) are restricted.
- 4 to 8 dS/m (Moderately saline): At this range, the yields of many common agricultural crops (such as maize, wheat, alfalfa, and cotton varieties) are significantly restricted.
- 8 to 16 dS/m (Strongly saline): Only tolerant crops (such as barley, sugar beet, and date palm) can produce satisfactory yields, while the yields of most other crops are severely reduced.
- > 16 dS/m (Very strongly saline): Only a few highly tolerant halophytes can survive and grow satisfactorily.
Since the question asks for the range where the yield of many common crops begins to be restricted, the moderately saline range of 4-8 dS/m is the standard correct range.

Step 3: Final Answer:
The yield of many crops is restricted at the range of 4-8 dS/m (Option B).