Certified Crop Advisor Practice Exam

A horizon that contained illuviated clay is the _____ horizon?

1. O Horizon

2. A Horizon

3. B Horizon

4. C Horizon

The correct answer is: A Horizon

The horizon that contains illuviated clay is the B horizon. This horizon is typically characterized by the accumulation of materials leached from the upper horizons, such as clay, iron, and organic compounds. The process of illuviation refers specifically to the deposition of these materials that have been transported down through the soil profile, usually as a result of water movement. In a typical soil profile, the B horizon is the layer that shows signs of this accumulation, distinguishing it from other horizons like the O (organic) horizon or the A (topsoil) horizon, which mainly contain organic matter and are characterized by biological activity. The C horizon, on the other hand, consists of weathered parent material and does not have the illuviated properties found in the B horizon. Understanding the properties and processes associated with these horizons is crucial for soil management and crop production practices, as they directly impact soil fertility, water retention, and the overall health of the soil ecosystem.