In which soil horizon would you find hardpan?

• A. A horizon
• B. B horizon
• C. C horizon
• D. E horizon

Answer: (B)

Hardpan forms when a dense, cemented layer develops in the subsoil as fine particles and mineral cementing agents accumulate there. This happens in the horizon where materials moving down from above (illuviation) collect and bind together—creating a compact, low-porosity layer that often restricts roots and water movement. In soil science, this suppressive layer is the subsoil horizon beneath the topsoil, where such accumulation and cementation are most common. The surface horizon is typically organic-rich and not cemented, the eluviation horizon (if present) is where leaching dominates, and the underlying parent material horizon remains relatively unaltered—so hardpan is characteristic of the subsoil horizon.