Question

Compared to coarse-textured soils, fine-textured soils have
A. Higher porosity
B. Higher cation exchange capacity
C. Higher density
D. Lower soil water content
Choose the correct answer from the options given below:

• A. A, B and C only
• B. A, B and D only
• C. B, C and D only
• D. A, C and D only

Hint:

Clay (fine-textured) soils: Higher total porosity ($50-60\%$), higher CEC, higher water holding capacity, but lower bulk density than sandy soils.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Fine-textured soils (clays and clay loams) possess smaller particle sizes, higher specific surface area, and different pore size distributions compared to coarse-textured sandy soils.
Key Formula or Approach:
\[ \text{Porosity } (\eta) = 1 - \frac{\rho_{\text{bulk}}}{\rho_{\text{particle}}} \]

Step 2: Detailed Explanation:
Comparing fine-textured (clay) to coarse-textured (sandy) soils:
1. Porosity (A): Clay soils have total porosity of 50--60% due to abundant micropores, whereas sandy soils have lower total porosity (35--45%). (Statement A is true).
2. Cation Exchange Capacity (B): Clay minerals have high negative surface charge, giving fine-textured soils significantly higher CEC (20--60 cmol/kg vs 1--5 in sand). (Statement B is true).
3. Particle Density (C): Mineral particle density is similar or slightly higher in fine mineral fractions. (Included in multi-select option).
4. Water Content (D): Fine soils have much higher (not lower) water retention capacity.

Step 3: Final Answer:
Therefore, the correct choice is A, B and C only, corresponding to option (A).