Major properties of soil order are:
A. Gelisols ‐ Occur in areas of cold region such as Artic, Antarctic or high mountains.
B. Histosols ‐ Organic matter rich (\(>\)20%) soils with peaty horizon under permanent water saturated environment.
C. Oxisols ‐ Deeply weathered soils of humid tropics with brick red colour.
D. Mollisols ‐ Dark coloured low base containing soils (\(<\)50% base saturated)
Choose the correct answer from the options given below:
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To remember the key soil orders:
- Gelisols \(\rightarrow\) Gelid (very cold/frozen).
- Histosols \(\rightarrow\) Tissue/Organic (peat/muck).
- Mollisols \(\rightarrow\) Soft/Fertile (high base saturation, \(>\)50%).
Step 1: Understanding the Concept:
The USDA Soil Taxonomy classifies soils into 12 major soil orders.
These orders are defined based on diagnostic surface and subsurface horizons, soil moisture regimes, and temperature regimes. Detailed Explanation:
Let us evaluate each statement:
- A. Gelisols: These are soils of cold climates that contain permafrost within two meters of the surface.
They are found primarily in polar regions and high mountain ranges.
Thus, Statement A is correct.
- B. Histosols: These are organic soils that form in waterlogged, anaerobic environments like bogs and peatlands.
They contain more than \(20\%\) organic matter by weight.
Thus, Statement B is correct.
- C. Oxisols: These are highly weathered soils of the humid tropics.
They are rich in iron and aluminum oxides (sesquioxides) and typically exhibit a distinctive brick-red color due to intense leaching.
Thus, Statement C is correct.
- D. Mollisols: These are fertile grassland soils characterized by a deep, dark-colored surface horizon (mollic epipedon).
By definition, Mollisols must have a high base saturation (greater than \(50\%\)), making them rich in calcium and magnesium.
Statement D claims they have low base saturation (\(<\) 50%), which is incorrect. (Soils with low base saturation are classified as Ultisols or Alfisols). Step 2: Final Answer:
The correct statements are A, B, and C only.
