Page 17 - World Reference Base for Soil Resources of Thailand

Land Development Department Library

Chapter 2

Key to the

Reference Soil

Groups

Table 4 Simplified guide to the WRB Reference Soil Groups (RSGs)
with suggested codes.

Key to the Reference Soil Groups RSG Code

1. Soils with thick organic layers:

Soils which are composed of organic materials Histosols HS
2. Soils with strong human influence

With long and intensive agricultural use: Anthrosols** AT

Containing significant amounts of artefacts: Technosols* TC

3. Soils with limitations to root growth
Permafrost-affected: Cryosols** CR

Shallow or with many coarse fragments: Leptosols LP

With a high content of exchangeable Na: Solonetz SN

Alternating wet-dry conditions, shrink-swell clays: Vertisols VR

High concentration of soluble salts: Solonchaks SC

4. Soils distinguished by Fe/Al chemistry
Groundwater-affected, underwater and in tidal areas: Gleysols GL

Allophanes or Al-humus complexes: Andosols** AN

Subsoil accumulation of humus and/or oxides: Podzols PZ

Accumulation and redistribution of Fe: Plinthosols PT
Low-activity clay, P fixation, many Fe oxides, strongly structured: Nitisols* NT

Dominance of kaolinite and oxides: Ferralsols FR

Stagnating water, abrupt textural difference: Planosols* PL

Stagnating water, structural difference and/or moderate textural difference: Stagnosols* ST

15