podzol

Podzol is a soil type defined by a characteristic eluviated-illuvial profile that develops under cool, moist climates, typically under coniferous or heath vegetation. The name reflects its origin in forested lands where acidic litter dominates. Podzols form by podzolization, a leaching process driven by organic acids and water movement that transports organic matter and iron and aluminum oxides downward.

In the soil profile, an E horizon often forms near the surface as silicate clays and oxides are leached, leaving a pale, relatively structureless horizon. Beneath the E horizon lies a spodic horizon (B) enriched in humus and fine accumulations of iron and aluminum oxides; this horizon is usually brown to reddish-brown and may show illuvial accumulations designated as Bhs or Bs. The A horizon, when present, is typically thin and strongly acidic. Overall base saturation is low, and soil pH commonly falls below 5.5.

Podzols are strongly weathered and nutrient-poor, with low cation exchange capacity. They form where rainfall is sufficiently high to drive leaching but temperatures are cool enough to slow mineral weathering and organic matter turnover. The result is a soil type that emphasizes eluviation of basic elements and translocation of organic matter and metal oxides.

Geographically, podzols are widespread in boreal and cool temperate regions, including much of northern Europe, Russia, Canada, and parts of the United States, often under forest or heath vegetation. They can support forestry but are generally not well suited to intensive agriculture without management interventions such as liming and nutrient amendments.

In modern classifications, podzols correspond closely to the Spodosol group of the USDA taxonomy, with the term podzol retained in some European classifications to describe similar soils.