In which soil horizon would you find hardpan?

The presence of hardpan is commonly associated with the B horizon in the soil profile. The B horizon, also known as the subsoil, is where materials leached from the upper horizons, such as clay, iron, or organic matter, accumulate. This accumulation can lead to a dense, compacted layer known as hardpan, which can restrict water movement and root penetration due to its reduced porosity and permeability.

In contrast, the A horizon is the topsoil, rich in organic matter and nutrients, typically more fertile and responsive to environmental changes. The C horizon consists of weathered rock or parent material, providing a transition to the bedrock but lacking the structure and features characteristic of more developed soils. The O horizon mainly consists of organic matter, such as decomposed leaves and other plant material, and is not where hardpan would form. Therefore, the B horizon is the correct choice when discussing the location of hardpan in the soil profile.