Which master horizon of soil is known as the zone of illuviation?

Correct option is C

The correct answer is (C) B horizon

Explanation:
• A soil profile is divided into several layers called "master horizons."
• Illuviation is the process of accumulation of materials (clay, iron/aluminum oxides, or humus) that have been washed down from the upper layers by water.
• The B horizon is the master horizon where this accumulation occurs. Therefore, it is technically called the zone of illuviation.
• It is located below the A or E horizons and usually has a finer texture (more clay) and a more developed structure than the layers above or below it.

Information Booster:
• Eluviation (spelled with an 'E') is the washing out or removal of materials from a horizon. The E horizon (or the lower part of A) is the zone of eluviation.
• The combination of A and B horizons is called the Solum (true soil).
• The combination of A, B, and C horizons is called the Regolith.

Additional Knowledge:
• O horizon (Option A): The organic horizon, composed primarily of organic matter at various stages of decomposition; usually found in forest soils.
• A horizon (Option B): The topsoil; it is the topmost mineral horizon, usually dark-colored due to organic matter. It is a zone of eluviation.
• C horizon (Option C): The parent material layer; it is composed of relatively unweathered rock material and lacks the properties of the A and B horizons.