Page 16 - World Reference Base for Soil Resources of Thailand

Land Development Department Library

Diagnostic horizon Soil taxonomy
properties and materials

Shrink-swell cracks Cracks that open and close periodically
Sideralic properties Requirements of oxic horizon except texture requirement

Soil organic carbon Requirement of organic Soil Material

Sombric horizon Sombric horizon

Spodic horizon Spodic horizon
Stagnic properties Episaturation or temporarily saturated with surface water

Strongly humic properties >1.4 g organic C 100 g soil in 100 cm of depth; assume bulk density
-1
1.5 Mg m -3
Sulfidic soil material Sulfidic material

Sulfuric horizon Sulfuric horizon

Takyric horizon** Clayey surface crust in flooded arid soils

Tephric soil material** Slightly weathered volcanic tephra
Terric horizon** Mineral material applied by humans

Thionic horizon Sulfuric horizon

Umbric horizon** Umbric epipedon

Vertic horizon more prominent of shrink-swell cracks, slickensides or wedge-shapedpeds
Vitric horizon** 10% or more volcanic glass

Yermic horizon** Surface layer of gravel, desert pavement

Remarks: ** not found in Thailand

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