What is the grain specific gravity for humus type soil ?
- A2·37
- B1·37Correct
- C4·37
- D3·37
Solution
Concept
Specific gravity of organic soils
Step-by-step solution
1. Mineral soils have G ≈ 2.6–2.8. 2. Organic matter is much lighter: humus G ≈ 1.37.
Explanation
Organic soils (peat, humus) have a low specific gravity of solids, in the range 1.1–1.4.
Why the other options are wrong
2.37, 3.37 and 4.37 are too high for organic matter.
Shortcut
Humus: 1.37; peat: 1.1–1.4; quartz: 2.65.
Common mistake
Using the mineral soil value.
Correct answer: B) 1·37