SOIL ATLAS OF ASIA 2ND EDITORIAL BOARD MEETING RURAL DEVELOPMENT ADMINISTRATION, NATIONAL INSTITUTE OF AGRICULTURAL SCIENCES, JEONJU, REPUBLIC OF KOREA | 29 APRIL – 3 MAY 2019

1. The IUSS (2014) endorsed both classification systems
ST and WRB as international systems

2. Differences in structure and principles
Number of categorical levels:
 ST has 6 levels
4 defined by key
 WRB has 2 levels in the system
1 defined by key
On the highest level:
 ST has 12 orders,
 WRB has 32 reference soil groups (RSG)
Soil moisture and temperature regimes:
 The WRB has no direct info on those

3. 1 piece of info
2 pieces of info
3 pieces of info
4 pieces of info
lots of info
no info, very regional
6 categories of classification
Hierarchical system of information
General
Specific

4. Soil Orders (First 6)
Soil
Order
Ending Characteristics, etc.
Entisol -ent Absence of distinct pedogenic horizons
(genetic profile A/C)
Inceptisol -ept Weak develop (genetic profile A/Bw/C)
Gelisol -el Permafrost, freeze-thaw
Histosol -ist Very high OM, wet (organic soils)
Andisol -and Volcanic soils
Aridisol -id Salt accumulation (carbonates, gypsum,
silica) – on larg dry areas of Earth!
Lessdeveloped

5. Soil Orders (last 6)
Soil Order Ending Characteristics, etc.
Vertisol -ert Swelling clays, high fertility
Mollisol -oll Dark, thick, grasslands
Ultisol -ult Moist & warm, acidic (low base)
Alfisol -alf Moist, forested, clay accumulation
Spodosol -od cool, wet, coarse, acidic
Oxisol -ox Extreme weathering, tropical forest, Fe,
Al oxides, old, stable PM
Welldeveloped

7. Entisols
Entisols are soils of recent origin. Most soils developed
in unconsolidated parent material with usually no genetic
horizons except an A horizon.
All soils that do not fit into one of the other 11 orders are
Entisols. Thus, they are characterized by great diversity.
Many Entisols are found in steep, rocky settings. However,
Entisols of large river valleys (floodplains) provide cropland
and habitat for millions of people worldwide.
Globally Entisols are extensive, occupying ~16% of the
Earth's ice-free land area.

9. Histosols
Histosols are soils that are composed mainly of organic
materials. They contain at least 20-30% organic matter by
weight and are more than 40 cm thick. Bulk densities are
quite low, often less than 0.3 g cm3.
Most Histosols form in settings such as wetlands. Histosols
are ecologically important because of the large quantities
of carbon they contain.
These soils occupy ~1.2% of the ice-free land area globally.

12. Gelisols
Gelisols are soils of very cold climates that contain
permafrost within 2 meters of the surface (freeze –thaw).
These soils are limited geographically to the high-latitude
polar regions and localized areas at high mountain
elevations.
Gelisols are estimated to occupy ~9.1% of the Earth's ice-
free land area Because of the extreme environment in
which they are found, Gelisols support only ~0.4% of the
world's population - the lowest percentage of any of the soil
orders.
Low soil temperatures cause decomposition of organic
materials to proceed very slowly. As a result, Gelisols store
large quantities of organic carbon.

13. freeze – thaw
cryoturbation

14. active layer
permafrost layer

15. Andisols
Andisols are soils that have formed in volcanic ash or other
volcanic ejecta. They differ from those of other orders in
that they typically are dominated by glass and poorly
crystalline colloidal materials.
As a result, Andisols have unique chemical and physical
properties that include high water-holding capacity and
the ability to 'fix' large quantities of phosphorus.
Globally, Andisols are the least extensive soil order and
only account for ~1% of the ice-free land area..

16. Stromboli
900 m

18. Inceptisols
Inceptisols have minimal horizon development.
They are more developed than Entisols, but still lack the
features that are characteristic of other soil orders.
Inceptisols are widely distributed and occur under a wide
range of ecological settings. They are often found on fairly
steep slopes, young geomorphic surfaces, and on resistant
parent materials.
A sizable percentage of Inceptisols are found in mountain
areas and are used for forestry, and recreation.
Inceptisols occupy an estimated 17% of the global ice-free
land area. Inceptisols support ~20% of the world's
population, also the largest percentage of soil orders.

20. Aridisols
Aridisols are CaCO3-containing soils of arid regions
that exhibit at least some subsurface horizon development.
They are characterized by being dry most of the year and
limited leaching. Aridisols contain subsurface horizons in
which clays, calcium carbonate, silica, salts, and/or gypsum
have accumulated.
Aridisols occupy ~12% of the Earth's ice-free land area.
Aridisols are used mainly for range, wildlife, and recreation.
Because of the dry climate in which they are found, they are
not used for agricultural production unless irrigation water is
available.

22. Vertisols
Vertisols are clay-rich soils that shrink and swell with
changes in moisture content. During dry periods, the soil
volume shrinks, and deep wide cracks form. The soil volume
then expands as it wets up. This shrink/swell action creates
serious engineering problems and generally prevents
formation of distinct, well-developed horizons (with slicken
sides) in these soils.
Globally, Vertisols occupy ~2.4% of the ice-free land area.

25. Slicken sides

26. Alfisols
Alfisols are moderately leached forest soils that have
relatively high native fertility. These soils are well
developed and have a subsurface horizon of clay
accumulation. Alfisols are mostly found in temperate
humid and subhumid regions of the world.
Alfisols occupy ~10.1% of the global ice-free land area.
Alfisols support about 17% of the world's population.The
combination of generally favorable climate and high native
fertility allows Alfisols to be very productive soils for both
agricultural and silvicultural use.

29. Mollisols
Mollisols are the soils of grassland ecosystems.
They are characterized by a thick, dark surface horizon.
This fertile surface horizon, known as a mollic epipedon,
results from the long-term addition of organic materials
derived from plant roots.
Mollisols primarily occur in the middle latitudes and are
extensive in prairie regions such as the Great Plains of the
US. Globally, they occupy ~7.0% of the ice-free land area.
Mollisols are among some of the most important and
productive agricultural soils in the world and are
extensively used for this purpose.

31. Spodosols
Spodosols are acid soils characterized by a subsurface
accumulation of humus with Al and Fe (spodic horizon).
These photogenic soils typically form in coarse-textured
parent material and have a light-colored E horizon
overlying the reddish-brown spodic horizon. The process that
forms these horizons is known as podzolization.
Spodosols often occur under coniferous forest in cool, moist
climates. Globally, they occupy ~4% of the ice-free land area.
Many Spodosols support forest. Because they are
naturally infertile, Spodosols require additions of lime in
order to be productive agriculturally.

35. Ultisols
Ultisols are „old” strongly weathered, leached and acid
forest soils with relatively low native fertility. Intense
weathering of primary minerals has occurred, and much Ca,
Mg, and K has been leached from these soils (very low base
saturation).
Ultisols have a subsurface horizon in which clays have
accumulated, often with strong yellowish or reddish colors
resulting from the presence of Fe oxides.
Ultisols occupy ~8.1% of the global ice-free land area and
support 18% of the world's population.
Agrcicilture is possible only with the use of fertilizer and
lime.

37. Oxisols
Oxisols are very highly weathered soils that are found
primarily in the intertropical regions of the world.
These soils contain few weatherable minerals and are often
rich in Fe and Al oxide minerals.
Oxisols occupy ~7.5% of the global ice-free land area.
Most of these soils are characterized by extremely low
native fertility, resulting from very low nutrient reserves,
high phosphorus retention by oxide minerals, and low
cation exchange capacity (CEC). Despite low fertility, Oxisols
can be quite productive with inputs of lime and fertilizers.

41. Development of soil orders

42. 2006: ftp://ftp.fao.org/agl/agll/docs/wsrr103e.pdf
2014: http://www.fao.org/3/a-i3794e.pdf
World Reference Base for Soil Resources

43. Basic principles
It comprises two tiers of categorical level:
1st level: Reference Soil Groups (RSGs)
The 32 RSGs are determined by key and serve
to delineate the broad soil regions.
2nd level: Set of principal and supplementary
qualifiers that are giving a precise description
on important properties and are added to the
name of the RSGs.

44. RULES FOR CLASSIFICATION (three steps)
The expression, thickness and depth of layers are
checked against the requirements of WRB diagnostic
categories, defined in terms of morphology and/or
analytical criteria.
(overlapping or coinciding possible)
Step 1 – the diagnostics

45. RULES FOR CLASSIFICATION
The combination of diagnostics compared with the WRB Key
in order to find the RSG, which is the first level of WRB
classification.
The user should go through the Key systematically!!!!
The soil belongs to the first RSG for which it meets all
specified requirements.
Step 2 – the key

46. RULES FOR CLASSIFICATION
For the second level of WRB classification, qualifiers
are used.
Step 3 – the qualifiers
Principal qualifiers:
are regarded as being most significant for a further
characterization of soils of the particular RSG.
They are given in a ranked order.
Supplementary qualifiers:
All other qualifiers (further details about the soil).
They are not ranked, but listed alphabetically.

47. Qualifiers 2014
The principal qualifiers are added before the name of
the RSG without brackets and without commas.
Priority order → The uppermost qualifier in the list is
placed closest to the name of the RSG.
The supplementary qualifiers are added in brackets
after the name of the RSG and are separated from each
other by commas, following the alphabetical order.
Qualifiers conveying redundant information are not
added.
Specifiers (→ subqualifiers) such as Epi-, Endo-, Amphi-,
Panto-, Thapto- Bathy-, Supra-, and Proto- indicate a
certain expression of the qualifier.

49. Page 79

50. Key to RSGs
Principal
qualifiers
Supplementary
qualifiers
Definition
↓
Reference Soil Group
(RSG)
List of the RSG
Priority list ↓
1
2
3
4
5
6
7
8
List of the RSG
Alphabetic list ↓
A
B
C
D
E
F
G
H
Classification name:
→
(B D)
←
4 1 RSG
Specifiers can be used to indicate
depth of occurrence, or to express
the intensity of soil characteristics

51. example

52. Step 1 Diagnostics
Mollic horizon
Cambic horizon
Argic Horizon
Calcic horizon

53. Step 2
The key

54. No chernic

55. Critirion 2. fails

56. Step 1 Diagnostics
Mollic horizon
Cambic horizon
Argic Horizon
Calcic horizon
65 cm

57. yes

58. PHAEOZEMS Principal qualifiers Supplementary qualifiers
Rendzic
Chernic/ Someric
Petroduric/ Duric
Petrogypsic
Petrocalcic/
Endocalcic
Leptic
Hortic/ Irragric/
Pretic/ Terric
Gleyic
Stagnic
Fluvic
Vertic
Greyzemic
Glossic/ Retic
Luvic
Cambic
Skeletic
Gypsiric
Dolomitic/ Calcaric
Haplic
Abruptic
Albic
Andic
Anthric
Arenic/ Clayic/Loamic/ Siltic
Aric
Chromic
Colluvic
Columnic
Densic
Ferralic/ Sideralic
Fractic
Hyperhumic
Isolatic
Nechic
Novic
Oxyaquic
Pachic
Ruptic
Endosalic
Sodic
Technic
Tephric
Tonguic
Transportic
Turbic
Vermic
Vitric
Luvic Endocalcic Phaeozem (Siltic, Aric)
Step 3 - The qualifiers