Acrisols

From Latin acris meaning sour, very acid, indicative of a low base saturation of the cation exchange capacity at pH 7.0.

Definition

Soils having

• 1. an argic horizon, which has a cation exchange capacity (in 1 M NH ₄OAc at pH 7.0) of less than 24 cmol _c kg ⁻¹ clay in some part, either starting within 100 cm from the soil surface, or within 200 cm from the soil surface if the argic horizon is overlain by loamy sand or coarser textures throughout, and

• 2. a base saturation of less than 50% (in 1 M NH ₄OAc at pH 7.0) in the major part between 25 and 100 cm.

General characteristics

Soils characterized by the presence of a well‐defined B horizon, with a blocky, prismatic, granular or massive structure (depending on water content, amount of Fe sesquioxides, and mineralogy of the fine fraction), which has a markedly increase in clay content (argic horizon) relative to the overlying horizons, and a cation exchange complex in which acidic cations (ionic Al species and, to a lesser extent, H ⁺,...