Page 134 - E-BOOK English

Podzols

Definition

Podzols are strongly acid soils with a spodic horizon, an illuvial horizon containing an
accumulation of black organic matter and/or reddish iron oxides within 200 cm from the surface

soil. This illuvial horizon is typically overlain by an ash-grey eluvial horizon. These soils occur in
humid areas in the boreal, temperate zones, and locally also in the tropics. The name Podzol
is widely used in national soil classification systems; other names for these soils are Spodosols
(China and the United States of America).

Distribution

Podzols cover an estimated 3,031 million rais worldwide, mainly in the temperate
and boreal regions of the Northern Hemisphere. They are extensive in Scandinavia, the

northwest of the Russian Federation, and Canada. Podzols are also presented in humid temperate
climates and the humid tropics. The tropical extent of Podsols is estimated at some 63 million
rais, mainly in residual sandstone weathering in perhumid region and alluvial quartz sands, e.g.,
in uplifted coastal areas. These areas are found along with the Rio Negro of Argentina,
French Guiana, Guyana, and Suriname in South America, in Southeast Asia (Kalimantan and Sumatra
of Indonesia), in Papua New Guinea, and northern and eastern Australia. They seem to be less
distribution in Africa.

In Thailand, Podzols occur about 639,548 rais in coastal areas of the east and south
regions.

Formation

Podzols are derived from strongly leaching, with highly acidic conditions, providing
conditions where a mor humus develops, and clay minerals are broken down. Iron and aluminum
are transported from the eluvial horizons by cheluviation. Changing of pH, wetting and drying,

microbial activity, and ageing of the chelation bonding are all responsible for the formation of
spodic horizons.

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