Page 25 - World Reference Base for Soil Resources of Thailand

Land Development Department Library

Acrisols

Definition

Acrisols have an argic horizon with a cation exchange capacity of less than 24 cmol kg
-1
c
clay (low activity clays) and a base saturation of less than 50% within a depth between 50 and
100 cm of the surface soil.

Distribution

Most extensive on acid rocks in Southeast USA, the southern fringes of the Amazon

basin, and both east and west Africa, Acrisols worldwide cover about 625 million rais. They are
associated with Nitisols, Ferralsols, Plinthosols, Lixisols, Arenosols, Regosols, and Cambisols.

In Thailand, all regions together, there is approximately 221 million rais (69.2%), mostly
covering the northeast, east, and south. These soils are mainly Clayic Rhodic Acrisols, Loamy

Haplic Acrisols, Loamy Gleyic Acrisols, Skeletal Skeletic Acrisols, and Loamy Haplic Acrisols/ Clayey
Gleyic Acrisols.

Formation

Acrisols are reddish or yellowish-brown freely drained and are acid soils of the humid

intertropical regions. The parent materials are strongly weathered
clays. Thereby they frequently have surface horizons in which clay

has been lost. Acrisols have an argic horizon, with low activity clays
and a base saturation of <50%. Leaching removes bases and the

breakdown-products of clay disintegration from the profile, further
producing more low activity clays. Clay eluviation is commonly

presented but exact illuviation features are occasionally found.

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