In which soil horizon would you find hardpan?

The B horizon is where hardpan is typically found. Hardpan refers to a dense layer of soil that is compacted and often impervious to water and roots. It forms as minerals leach down from the upper layers of soil, particularly through processes like illuviation, where particles and nutrients are deposited in the B horizon from the A horizon above. This accumulation can lead to a hard, compact layer that restricts water drainage and root penetration.

In contrast, other horizons serve different functions. The A horizon, known as the topsoil, is rich in organic matter and supports much of the biological activity in the soil. The C horizon consists of partially weathered rock and material from which the soil forms, while the O horizon is composed of organic matter such as decomposed leaves and plants. These horizons do not typically develop the same density or compact nature associated with hardpan found in the B horizon.