Page 125 - E-BOOK English

The representatives of Plinthosols in Thailand

Haplic Plinthosols

Haplic Plinthosols have a typical expression

of certain features and only used if none of the
preceding qualifiers applies.

Na Tham series (Ntm) is a representative
of Haplic Plinthosols. Na Tham soils are formed

from alluvium over fine grain clastic rocks (shale and
phyllite) and occurred on alluvial fan distributing in

the South of Thailand. Relief is gently undulating to
undulating with slopes ranging from 2 to 12 percent.
These soils occupy moderate extent in peninsular

and some areas in southeast coast of Thailand.
Drainage is well to moderately well drained,

permeability is estimated to be moderate and surface
runoff is medium. They are moderately deep
soils to ironstones and characterized by a very dark

grayish brown or dark brown fine sandy loam surface
or A horizon overlying a strong brown or yellowish
brown fine sandy clay loam upper argillic B horizon.

These in turn overly a mixed brownish very gravelly
sandy clay loam (very gravelly clay loam) lower
argillic B horizon which is underlain by a mottled

clay or clay loam accompanying with plinthite of
more than half of the soil matrix. Gravels are

mainly composed of ironstones which may include
rounded or subrounded rock pebbles. Reddish and
grayish mottles are presented in common throughout

the argillic B horizon. Reaction is very strongly acid
to strongly acid (pH 5.0-5.5). Low fertility and

moderately deep are limitation for land use.

123