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Q124
(NDA-II/2023)
Geography › World Physical Geography
Official Key
Which one of the following is an organic soil?
Explanation
Histosols are defined under the USDA Soil Taxonomy as soils that consist primarily of organic materials. The name is derived from the Greek word 'histos', meaning tissue. These soils contain a very high concentration of organic matter (typically more than 20-30% by weight) and are usually found in wetland environments like bogs, moors, and peatlands, where poor drainage inhibits the rapid decomposition of plant matter.
- Aridisols: These are mineral soils of dry/arid regions with very low organic content.
- Oxisols: These are highly weathered soils of tropical and subtropical regions, characterized by iron and aluminum oxides.
- Vertisols: These are clay-rich soils known for significant shrinking and swelling (e.g., India's Black Cotton Soil).
Since Histosols are the only order characterized by dominant organic horizons, Option B is the correct answer.
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