- the subsoil in a soil profile.
- the layer of a soil profile immediately below the A horizon, containing deposits of leached material
- In ABC soil, the second and middle zone, characterized by an accumulation of soluble or suspended organic material, clay, iron, or aluminum. These materials originate in the A horizon and are transported to the B horizon through the process of eluviation. B horizons often have a blocky structure and are reddish in color due to the presence of oxidized metals. Also called zone of accumulation zone of illuviation