What is a fragipan?

• A. Hard and dense, nearly impermeable subsurface layer of soil that will prevent root growth
• B. A nutrient-rich topsoil layer
• C. A water-logged surface layer
• D. A deep, well-drained loamy layer

Answer: (A)

Fragipans are hard, dense, brittle subsoil layers that are nearly impermeable and resist root growth. This compact horizon sits below the topsoil and has low porosity and poor drainage, so roots have trouble penetrating it and water movement can be restricted, which can affect plant health and soil structure. That’s why the description of a hard, dense subsurface layer that prevents root growth best matches what a fragipan is.

The other options describe parts or conditions of soil thatFragipan is not: a nutrient-rich topsoil layer refers to the surface horizon rich in organic matter and nutrients; a water-logged surface layer describes a saturated surface horizon, not a compact subsurface layer; a deep, well-drained loamy layer describes a good-draining, productive horizon, not a dense, restrictive one.