eluviatielaag

Eluviatielaag is a term used in soil science to describe a pedogenic layer in a soil profile where eluviation and illuviation processes operate. The concept is often used in Finnish pedology and corresponds to the zone in which soluble and fine constituents are leached from the upper part of the profile and deposited in lower horizons. In practice, eluviatielaag commonly involves an eluviated horizon (E) resting above an illuvial horizon (for example Bt), though the term can be employed to describe the functional zone consisting of both processes.

Formation and characteristics: In well-drained, permeable soils, infiltrating water removes clay, organic matter, iron oxides, and carbonates from the upper portions of the profile. This creates an eluviated horizon with a lighter color and reduced clay and humus content. The removed materials accumulate in the lower horizon, forming an illuvial horizon that shows higher clay content, oxide accumulation, and distinct color or structural features. The boundary between eluviated and illuvial materials often marks a noticeable change in texture and color.

Diagnostic features and distribution: An eluviated horizon typically has lower color value and chroma, with reduced structure and humus. The underlying illuvial horizon may display clay skins, nodules, or mottling associated with clay and oxide enrichment. Eluviatielaag is most commonly discussed in temperate to subtropical soils, and is a key concept in classifications that distinguish eluviation and illuviation, such as Luvisols and Alfisols in various soil reference systems. In Nordic contexts, the term aligns with the E horizon (eluviation) and the Bt horizon (illuviation) as part of the same zone.