Alisols

Alisols are strongly acid, generally unproductive soils, with accumulated high activity clays in their subsoils. Al dominates the exchange complex. The following is derived from FAO (2001).

Connotation. Strongly acid soils with subsurface accumulation of high activity clays that have more than 50% Al ³⁺ saturation; from L. aluminium, alum.

Synonyms. ‘Red yellow podzolic soils’ with high‐activity clays (Brazil), ‘ultisols’ with high‐activity clays (Soil Taxonomy) and ‘fersialsols’ and ‘sols fersiallitiques très lessivés’ (France).

Definition. Defined by FAO (2001) as soils with

• 1. an argic horizon, which has a cation exchange capacity (1 M NH ₄OAc at pH 7.0) of 24 cmol(+)kg ⁻¹ clay or more, 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. alic properties in most of the layer between 25 and 100 cm from the soil surface, and

• 3....