Savikerros

Savikerros is a term used in Finnish soil science to describe a soil layer in which the clay content increases markedly compared with the layers above and below it. The term is commonly applied to horizons formed by clay illuviation, often corresponding to a Bt or argic horizon in broader soil classification.

Formation and occurrence: Savikerros typically develops when clay minerals are transported with water from upper, coarser horizons and accumulate in the lower part of the soil profile. The resulting layer is usually finer textured, denser, and more cohesive than surrounding horizons, and it may show distinct color or soil-mantle properties due to mineral changes and oxidation. Savikerros is found in many soil types and landscapes, including temperate regions where illuviation processes are active.

Properties: A savikerros has high fine particle content, increased plasticity when moist, and relatively low permeability compared with overlying layers. It often exhibits strong cohesive strength and shrink–swelling tendencies, which can influence soil structure, drainage, and root growth. The layer also enhances nutrient retention, particularly for cations, but can impede drainage and aeration if its thickness is substantial.

Implications: For land use and engineering, a savikerros can affect drainage efficiency, perched water tables, and root penetration, and it may pose challenges for construction foundations and excavations. Management choices, such as drainage improvements or controlled subsoil tillage, are sometimes employed to mitigate its effects on cultivation and stability.

In Finnish soil literature, savikerros serves as a practical description of a clay-enriched horizon and is linked to the broader concept of illuviation in soil profile development.