Question

The standard 'A' horizon of soil usually consists sub-horizons which are,

• A. Rich in organic matter and intimately mixed with mineral water
• B. Poor in organic matter
• C. Average organic horizon with low bulk density
• D. Organically poor and with salt particles

Hint:

Master horizons:
O = Organic surface layer
A = Topsoil (Mineral matter mixed with humus)
E = Eluvial/leached horizon
B = Illuvial subsoil
C = Parent material.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The soil profile is organized into master genetic horizons (O, A, E, B, C, R) formed through pedogenic soil development processes.

Step 2: Detailed Explanation:
In standard soil taxonomy and pedology:
- The A Horizon (topsoil surface mineral horizon) forms at the surface or below an O horizon.
- It is characterized by the humification and accumulation of decomposed organic matter intimately mixed with the mineral soil fraction.
- It is the primary zone of biological activity, root proliferation, and nutrient cycling.

Step 3: Final Answer:
Therefore, the A horizon is Rich in organic matter and intimately mixed with mineral matter, corresponding to option (A).