Question

Match List-I with List-II

List-I (Soil type) & List-II (Bulk density (Mg $m^{-3}$))
(A) Peat & (I) 2.0
(B) Compact & (II) 1.1 to 1.4
(C) Fine textured & (III) 1.4 to 1.75
(D) Coarse textured & (IV) 0.5

• (A) - (IV), (B) - (I), (C) - (II), (D) - (III)
• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (II), (B) - (IV), (C) - (I), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

Keep these rules in mind:
- Organic soils (Peat): Lowest bulk density ($\approx 0.5$).
- Clay soils (Fine-textured): Lower bulk density than sandy soils ($1.1-1.4$) due to high total microporosity.
- Compacted soils: Highest bulk density ($\approx 2.0$).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Bulk density ($\rho_b$) is the mass of dry soil divided by its total volume (including both solids and pore spaces).
It is expressed in megagrams per cubic meter ($\text{Mg/m}^3$) or grams per cubic centimeter ($\text{g/cm}^3$).
Bulk density is inversely proportional to soil porosity.

Step 3: Detailed Explanation:
Let us match each soil type with its typical bulk density range:
- (A) Peat $\rightarrow$ 0.5 (IV): Peat is an organic soil composed predominantly of highly porous organic residues.
Because organic matter has a very low particle density and peat contains massive pore space, its bulk density is exceptionally low, typically around 0.5 $\text{Mg/m}^3$.
- (B) Compact $\rightarrow$ 2.0 (I): Severely compacted soils (such as heavily trafficked subsoils or hardpans) have lost almost all their pore space.
Because the bulk volume is dominated almost entirely by solid mineral mass, the bulk density reaches very high values, around 2.0 $\text{Mg/m}^3$.
- (C) Fine textured $\rightarrow$ 1.1 to 1.4 (II): Fine-textured soils (clays and clay loams) have high total porosity due to abundant micro-pores.
Consequently, their bulk density is relatively low, typically ranging from 1.1 to 1.4 $\text{Mg/m}^3$.
- (D) Coarse textured $\rightarrow$ 1.4 to 1.75 (III): Coarse-textured soils (sands and sandy loams) have lower total porosity because they lack micro-pores.
Consequently, their bulk density is higher, typically ranging from 1.4 to 1.75 $\text{Mg/m}^3$.
This matching sequence gives: (A) - (IV), (B) - (I), (C) - (II), (D) - (III).
This matches Option (A).

Step 4: Final Answer:
The correct matching sequence is (A) - (IV), (B) - (I), (C) - (II), (D) - (III).