duripans

A duripan is a subsurface soil horizon that is hardened by cementation with silica. The indurated layer is typically found in the lower part of the B horizon or just beneath the A horizon, and it resists penetration by common tools because the silica cement binds the grains of clay and silt together.

Formation occurs as silica is mobilized with soil-water movement and precipitates within the horizon, cementing grains into a dense, relatively impermeable layer. The cementing agent is primarily silica (silicon dioxide), though minor amounts of other cementing materials can be present. This cementation reduces pore space, lowers permeability, and can impede root growth and vertical water movement.

Duripans are most commonly associated with arid and semi-arid regions, where rainfall is limited and evaporation is high, promoting silica precipitation and horizon induration. They occur in soils classified within several orders, most notably Aridisols, and can appear in other soil types under suitable climatic and geological conditions.

Key identifying features include a hard, brittle, and resistant horizon that is difficult to break with common hand tools. The horizon often has a muted color contrast with adjacent layers and shows little sign of ongoing biological activity due to restricted permeability. It is distinguished from other pans by its silica-based cementation rather than carbonate (caliche) or clay-based cement.

Impact and management considerations: the duripan restricts drainage and root penetration, influencing water availability and vegetation patterns. In agricultural or reclamation contexts, the presence of a duripan complicates irrigation planning and soil loosening, and may limit deep rooting and effective water use.