TRUE OR FALSE 1. The O horizon is the zone of least weathering with a high conce
ID: 287495 • Letter: T
Question
TRUE OR FALSE
1. The O horizon is the zone of least weathering with a high concentration of organic matter but low activity of soil microorganisms.T/F
2. An illuvial horizon charaterized by the accumulation of carbonates will be labeled EK (hint: k stands for carbonates). T/F
3. A soil profile has the following sequences O,A2,B3: This profile has 3 master horizons and 5 subhorizons. T/F
4. Mollisols have soft mollic epipedon but thin accumulation of organic matter. T/F
5. A major characteristic of Vertisols is that they swell and shrink leading to the development of cracks. T/F
6.The presence of Allophane is a unique characteristic of Andisols. T/F
Explanation / Answer
1. TRUE. In the O- horizon, the "O" stands for organic matter and contains no weathered material.
2. FALSE. The E horizon is a zone of elluviation or profound leaching. It is the zone of greatest eluviation and is very leached of clay, chemicals, and organic matter so it cannot be characterised by the accumulation of carbonates. In a soil profile, the B-horizon is the elluvial horizon or the zone of accumulation.
3. FALSE. A soil profile having following sequences O,A2,B3 has 3 master horizons and 4 subhorizons. O, A and B are the 3 master horizons and the four subhorizons are O1, O2, A2 & B3.
4. FALSE. The correct statement should be: Mollisols have soft mollic epipedon and thick accumulation of organic matter. Mollic epipedons result from the long-term addition of organic materials derived from plant roots, and typically have a soft, granular, soil structure. These soils have thick, dark surface horizons relatively high in organic matter.
5. TRUE. Vertisols are the clay-rich soils that contain a type of expansive clay which exhibit swelling and shrinking features upon wetting and drying leading to the development of deep wide cracks.
6. TRUE. The presence of Allophane is a unique characteristic of Andisols. Most of the unique properties of Andisols are related to their colloidal fraction. Allophane and imogolite are hydrated aluminosilicate minerals exhibiting short-range order crystallinity and these minerals can strongly influence soil chemical processes due to their high surface area and reactivity. They are common in soil orders of Andisols and Spodosols.
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