Question

Mineral particles less than 2 mm in equivalent diameter,ranging between specified size limits is _______

• A. Ped
• B. Soil separates
• C. Soil order
• D. Stoniness

Hint:

Soil separates are the individual mineral particles (sand, silt, and clay) with diameters $< 2.0\text{ mm}$.
The relative proportion of these separates determines the soil's textural class.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Soil texture refers to the relative proportions of sand, silt, and clay mineral particles in a soil.
These individual particles are classified into standardized size categories called soil separates or soil fractions.

Step 2: Detailed Explanation:
Soil mineral particles with diameters less than $2.0\text{ mm}$ are grouped into specific size fractions called soil separates:
1. Sand: Particles ranging from $2.0\text{ mm to }0.05\text{ mm}$ in diameter (according to the USDA system).
2. Silt: Particles ranging from $0.05\text{ mm to }0.002\text{ mm}$ in diameter.
3. Clay: Fine particles with diameters less than $0.002\text{ mm}$ ($2\text{ }\mu\text{m}$).
Particles larger than $2.0\text{ mm}$ (such as gravel, cobbles, and stones) are classified as coarse fragments or gravels and are excluded from soil texture determinations, although they contribute to "stoniness."
Let us review the other options:
- Ped: A naturally occurring soil aggregate composed of clustered soil separates.
- Soil order: The highest hierarchical category in soil taxonomy (such as Alfisols or Vertisols).
- Stoniness: Refers to the proportion of surface or subsurface soil occupied by gravels and stones larger than $2.0\text{ mm}$.

Step 3: Final Answer:
Mineral particles less than $2\text{ mm}$ grouped into specific size limits are called Soil separates, which corresponds to Option (B).