Question
Although, profiles of different types of soil differ markedly with respect to their physicochemical and biological properties; the following diagram shows a typical hypothetical soil profile with its 5 principal horizons [O to R].
Study the given diagram. The characteristics [Q to U] related to various horizons and the names of horizons [i to v] are tabulated below:
| Characteristics | Horizons |
|---|---|
| (Q) Solum | (i) O2 |
| (R) Podsolic Zone | (ii) A₁ |
| (S) Fairly decomposed mater - 'Duff' | (iii) $A + B$ |
| (T) Melanized Region | (iv) A |
| (U) Zone of Eluviation | (v) A2 |
Make the correct matches of the characteristics [Q to U] with the horizons [i to v] and choose the correct option :
Options
Solution
Sol. Key concept: Soil horizons reflect organic accumulation, leaching and deposition.
Q–(iii): In the simplified older scheme used in the figure, the solum or developed soil includes the A and B horizons. C is relatively little-altered parent material, and R is bedrock.
R–(v): The pale, leached A₂ layer is the podsolic or strongly eluviated zone. S–(i): O₂ contains more decomposed organic matter, traditionally called duff, below the fresher O₁ litter.
T–(ii): A₁ is darkened by humus, so it is the melanized region. U–(iv): The key uses A broadly for the zone from which materials are removed by downward-moving water. These matches give option (c).
Correction / clarification: More precisely, strong eluviation is characteristic of A₂ in this older notation, corresponding broadly to the E horizon in modern classifications. Do not infer that all A horizons are equally leached; modern descriptions also include E within the solum. [R4]
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