Page 68 - E-BOOK English

Fluvisols

Definition

Fluvisols have a thick fluvic soil material of 25 cm within 50 cm from the surface soil and
no horizons other than a histic, mollic, ochric, umbric, takyric, yermic, salic, histic, and sulfuric.

Fluvisols include Thionic, Histic, Gelic, Salic, Gleyic, Mollic, Umbric, Arenic, Tephric, Stagnic, Humic,
Gypsiric, Calcaric, Takyric, Yermic, Aridic, Skeletic, Sodic, Dystric, Eutric and Haplic.

Distribution

Fluvislos worldwide cover about 2,188 million rais. Half of the total Fluvisols occurs in
the tropical region, including river floodplains, deltaic areas, and coastal marine lowlands. These

soils are frequently associated with Histosols and Gleysols.
In Thailand, Fluvisols countrywide distribute 2.9 million rais, covering in the north,

central where the main rivers present, and coastal areas in the southern part of the country.

Formation

Fluvisols are derived from accumulating alluvial deposits. Soil formation occurs upon

layered alluvial sediment, each with a different organic matter content. In coastal areas, alluvial
accumulations may contain sulfidic soil material or a sulfuric horizon, which oxidizes to give acid

sulfate soil when drained.
These soils frequently occur with other soils dominated by alluvial deposits as influenced

by water, including Arenosols, Cambisols, Gleysols, and Solonchaks, as well as associated with
those soils with low development such as Leptosols and Regosols.

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