Question

Volumetric composition of soil solid is:

• A. 25%
• B. 45%
• C. 50%
• D. 5%

Hint:

Remember the \( 50-50 \) rule.
Soil is \( 50\% \) stuff (solids) and \( 50\% \) space (pores).
If the question asks for "Mineral matter" specifically, the answer is \( 45\% \). If it asks for "Organic matter," it is \( 5\% \).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the total volume occupied by the solid phase (mineral + organic matter) in a typical, ideal loam soil.
Detailed Explanation:

• The Ideal Soil Model:
In soil science, an "ideal" surface soil is considered to have a balanced volume distribution to support plant life.
The total volume is divided into two main categories: Solid Space and Pore Space.

• Solid Phase Composition (50%):
The solids occupy exactly half of the total soil volume in a healthy, uncompacted soil.
Within this \( 50\% \) solids:
- Mineral matter accounts for about \( 45\% \).
- Organic matter accounts for about \( 5\% \).

• Pore Phase Composition (50%):
The other half is the pore space, which ideally contains:
- Soil Water (\( 25\% \)).
- Soil Air (\( 25\% \)).

• Variability:
In sandy soils, pore space might be lower (\( 35-40\% \)).
In clayey soils, pore space can be higher (\( 50-60\% \)).
When soil is compacted, the solid percentage increases as pores are crushed.

Step 2: Final Answer:
A standard, healthy soil is composed of \( 50\% \) solids by volume.