Page 158 - E-BOOK English

Pellic Vertisols

Pellic Vertisols have a Munsell colour value

of ≤ 3 and a chroma of ≤ 2, both moist in the upper
30 cm of the soil.

Lop Buri series (Lb) is a representative

of Pellic Vertisols. Lop Buri soils are formed from
alluvium which is rich in montmorillonitic clay,

underlying marl layer and occur on terraces
adjacent to limestone hills in central of Thailand.

Relief is nearly flat to slightly undulating. Slopes
are 1 to 5 percent. Drainage is well drained.

Permeability is slow and runoff is slow to moderate.
The soil dries and cracks deeply during the dry

season. They are deep neutral to moderately
alkaline soils and characterized by a very thick black

or very dark gray clay A horizon overlying a black or
very dark gray coloured B horizon. Slickensides and

pressure faces are characteristic of the dark coloured
B horizon. The marl layer has its upper boundary at

some depth below 80 cm from the surface soil and
scattered secondary lime nodules occur throughout.

Cracks width ≥ 1 cm at 50 cm depth open for long
periods during the dry season. Soil pH is slightly

acid to strongly alkaline (pH 6.5-9.0). In the dry area,
cracks of this soil negatively influence agricultural

applications such as tillage, whereas this problem is
less in humid or irrigated areas.

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