83

Distribution and Classification of Volcanic Ash Soils
Tadashi TAKAHASHI1* and Sadao SHOJI2
1

Graduate School of Agricultural Science, Tohoku University
1-1, Tsutsumidori, Amamiya-machi, Aoba-ku, Sendai, 981-8555 Japane-mail: tadashi@bios.tohoku.ac.jp
2
Professor Emeritus, Tohoku University
5-13-27, Nishitaga, Taihaku-ku, Sendai, 982-0034 Japan*corresponding author

Abstract
Volcanic ash soils are distributed exclusively in regions where active and recently extinct
volcanoes are located. The soils cover approximately 124 million hectares, or 0.84% of the world’s
land surface. While, thus, volcanic ash soils comprise a relatively small extent, they represent a crucial
land resource due to the excessively high human populations living in these regions. However, they
did not receive worldwide recognition among soil scientists until the middle of the 20th century.
Development of international classification systems was put forth by the 1978 Andisol proposal of G. D.
Smith. The central concept of volcanic ash soils was established after the finding of nonallophanic
volcanic ash soils in Japan in 1978. Nowadays, volcanic ash soils are internationally recognized asAndisols in Soil Taxonomy (United States Department of Agriculture) and Andosols in the World
Reference Base for Soil Resources (FAO, International Soil Reference and Information Centre andInternational Society of Soil Science). Several countries including Japan and New Zealand havedeveloped their own national classification systems for volcanic ash soils. Finally correlation of theinternational and domestic classification systems is described using selected volcanic ash soils.
Key words: Andisols, Andosols, Japanese Cultivated Soil Classification, New Zealand Soil
Classification, Soil Taxonomy, World Reference Base for Soil Resources (WRB)

1. Introduction
The term “volcanic ash soils” is commonly used todenote “Kurobokudo,” meaning black-fluffy soils inJapanese (The Third Division of Soils, 1973),“Andosols” in the World Reference Base for Soil
Resources (WRB Classification) (FAO et al., 1998)
and “Andisols” in US Soil Taxonomy (Soil Survey
Staff, 1999). The soil names of Andosols and Andisols are derived from “Ando soils” whose etymology
is dark (An) and soils (do) in Japanese.
Volcanic ash soils occur extensively, closely paralleling the global distribution of active and recently
extinct volcanoes, have unique properties, andsignificantly contribute to agriculture and forest production. However, they did not receive worldwide
recognition among soil scientists until the middle ofthe 20th century. It was only in 1960 that “volcanic
ash soils” were identified for the first time in aninternational system of soil classification.
Volcanic ash soils were first included as the Andept suborder of Inceptisols in the Seventh Approximation (Soil Survey Staff, 1960) and this suborder
was introduced into Soil Taxonomy (Soil Survey Staff,

1975). In 1978 Smith (1978) proposed reclassification of Andepts and provided a rationale for development of a new soil order, Andisols. His proposal led
to the development and establishment of the current
international classification of Andisols (Soil Survey
Staff, 1999). During this period, the FAO/Unesco
held a meeting on the classification of volcanic ash
soils in Japan in 1964 (FAO/Unesco, 1964) anddesignated the major soil group Andosols for the Soil
Map of the World (FAO/Unesco, 1974). Andosols
are currently included as one of 30 reference soil
groups of the World Reference Base for Soil
Resources (WRB Classification) (FAO et al., 1998).
Several countries including Japan and New
Zealand have developed their own national classification systems for volcanic ash soils. Each national
system organizes knowledge of the distribution, properties, productivity, utilization, and management ofsoils in its respective jurisdiction. However, thenational systems are not in competition with the international systems. They are rather complementaryand provide the basic information and data needed forthe development of the more comprehensive international systems.

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T. TAKAHASHI and S. SHOJI

This paper first briefly outlines the distribution of
volcanic ash soils and then describes internationalclassification systems (Soil Taxonomy and WBRClassification) and domestic classification systems(Japanese Cultivated Soil Classification and New
Zealand Soil Classification) for volcanic ash soils.
Lastly, some selected soil profiles are introduced andtheir classification is tested according to these soil
classification systems.

2. Geographic Distribution of Volcanic Ash
Soils
Soils derived from volcanic materials (Andisols)
are distributed exclusively in regions where active andrecently extinct volcanoes are located as shown in
Fig. 1. This soil resources map is derived from thefront cover page of Keys to Soil Taxonomy (Soil Survey Staff, 1998). The principal regions of the world
where Andisols are distributed are summarized(Leamy, 1984) as follows:- In Europe: Italy, Sicily, Sardinia, France (Massif– Central).
- In Africa and the Indian Ocean: Kenya, Rwanda,
Tanzania, Ethiopia, Cameroon, Malagasy, Reunion,
Canary Islands, Uganda, Sudan, Zaire.
- In America: Alaska, British Columbia, Washington, Oregon, California, Mexico, Costa Rica, Panama,
Honduras, Guatemala, El Salvador, Nicaragua, West
Indies, Ecuador, Colombia, Peru, Chile, Argentina,
Bolivia.
- In Asia and the Pacific: Hawaii, Aleutian Islands,
Kamchatka, Japan, Korea, Micronesia, Philippines,
Indonesia, Papua New Guinea, Solomon Islands,
Vanuatu, Fiji, Samoa, Tonga, New Zealand.
Volcanic ash soils cover approximately 124 million
hectares or 0.84% of the world’s land surface (Leamy
1984). Approximately 60% of volcanic ash soils
occur in tropical countries. While volcanic ash soils
comprise a relatively small extent of the world’s
surface, they represent a crucial land resource due tothe disproportionately high human populations livingin these regions.
Eighty-six active volcanoes are recognized inJapan (Japan Meteorological Agency, 2001) andanother 21 volcanoes will be included as “active” inthe near future. Active volcanoes are concentrated infour districts: Hokkaido, Tohoku, Kanto and Kyushu.
Therefore, volcanic ash soils are mainly distributed inthese districts (Fig. 2) and cover 18% of the territoryof Japan. Cultivated volcanic ash soils occupy approximately 1.35 million hectares, comprising 27% of
the total agricultural land use in Japan. Therefore,
these soils are important resources for agriculture,especially for upland crop production.

3. Classification of Andisols in Soil Taxonomy
The current classification of Andisols included in
Soil Taxonomy (Soil Survey Staff, 1999) is the mostwidely used system for the international classificationof volcanic ash soils. The development of this classification had its origin in the Andisol proposal put forth
by Smith in 1978 and was further developed throughthe collective experience and efforts of members of
the International Committee on the Classification ofAndisols (ICOMAND) for ten years from 1978 to
1988. On the basis of the final report of the
ICOMAND (Leamy et al., 1988), the Andisol order
was established for Soil Taxonomy in October of 1989
and it was first published in the 4th edition of Keys toSoil Taxonomy (Soil Survey Staff, 1990). After several revisions were conducted, the current classificationof Andisols was completed (Soil Survey Staff, 1999).
The central concept of Andisols is that of a soil developing in volcanic ejecta and/or volcaniclastic material, whose colloidal fraction is dominated byshort-range-orderminerals,
and/orAl-humuscomplexes. Based on characteristics of Andisols,
andic soil properties are defined as listed in Table 1.
Criterion 1 in the definition of andic soil properties
is used to classify Andisols that show a high degree of
weathering as determined by ammonium oxalate extractable Al plus a half of Fe (Alo + 1/2 Feo). Suchsoils typically have high phosphate retention and low
bulk density. Criterion 2 is applied to classify Andisols which are vitric or have developed from mixed
parent materials of tephra and non-tephra deposits.
Soils with mixed parent materials typically have highbulk densities (> 0.9 g cm–3) so they fail to meet andic
soil properties as defined by criterion 1. Therefore,
the bulk density requirement is waived in criterion 2
and a phosphate retention of > 25% requirement isincluded to separate Andisols from Entisols (Shoji etal., 1987). Criterion 2 is further used to define andic
soil properties in soils showing a low degree of weathering or vitric properties. It has two requirements
consisting of minimum concentrations of glass content
and Alo + 1/2 Feo.
The definition of Andisols in Soil Taxonomy (SoilSurvey Staff, 1999) is based on the existence of subhorizons meeting requirements of andic soil properties
which have a cumulative thickness of 36 cm or more
within 60 cm of either the mineral soil surface or the
top of an organic layer with andic soil properties(Table 2). Andisols are keyed out after Spodosols
and before Oxisols (Soil Survey Staff, 1999).
The classification of suborders and great groups ofAndisols is shown in Table 3. Seven suborders areprovided for the Andisol order: Aquands, Cryands,
Torrands, Xerands, Vitrands, Ustands, and Udands.
These suborders are defined based on soil temperatureand soil moisture regimes except for Vitrands. They
are subdivided into great groups mainly based on
important constraints to agricultural production.

Fig. 1 Worldwide distribution of volcanic ash soils (Andisols).
(World Soil Resources Staff, 1997; copyright USDA, Natural Resources Conservation Service, with permission.)

Distribution and Classification of Volcanic Ash Soils
85

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T. TAKAHASHI and S. SHOJI

Fig. 2 Distribution of allophanic and nonallophanic volcanic ash soils in Japan(courtesy of N. Matsuyama and M. Saigusa).

Table 1

Definition of andic soil properties in Soil Taxonomy (Soil Survey Staff, 1999).

To be recognized as having andic soil properties, soil materials must contain less than 25% (by weight) organic carbon
and meet one or both of the following requirements:
1. In the fine-earth fraction, all of the following:a. Aluminum plus 1/2 iron percentage (by ammonium oxalate) totaling 2.0% or more, andb. A bulk density, measured at 33 kPa water retention, of 0.90 g/cm3 or less, andc. A phosphate retention of 85% or more; or
2. In the fine-earth fraction, a phosphate retention of 25% or more, 30% or more particles of 0.02 to 2.0 mm in size,and one of the following:a. Aluminum plus 1/2 iron percentage (by ammonium oxalate) totaling 0.40 or more and, in the 0.02 to 2.0 mm
fraction, 30% or more volcanic glass; orb. Aluminum plus 1/2 iron percentage (by ammonium oxalate) totaling 2.0 or more and, in the 0.02 to 2.0 mm
fraction, 5% or more volcanic glass; orc. Aluminum plus 1/2 iron percentage (by ammonium oxalate) totaling between 0.40 and 2.0 and, in the 0.02 to
2.0 mm fraction, enough volcanic glass that can be determined according to the following equation: Volcanic
glass (%) > 36.25 – 15.62 × (aluminum plus 1/2 iron percentages).

Table 2

Definition of Andisols in Soil Taxonomy (Soil Survey Staff, 1999).

Other soils that have andic soil properties in 60% or more of the thickness either:
1. Within 60 cm either of the mineral soil surface or of the top of an organic layer with andic soil properties, whicheveris shallower, if there is no densic, lithic, or paralithic contact, duripan, or petrocalcic horizon within that depth; or
2. Between either the mineral soil surface or the top of an organic layer with andic soil properties, whichever isshallower, and a densic, lithic, or paralithic contact, a duripan, or a petrocalcic horizon.

Distribution and Classification of Volcanic Ash Soils

Aquands: These are Andisols having an aquicmoisture regime caused by restricted drainage as
imposed by depressed landscape position or the
existence of impermeable layers.
Aquands are formed in volcanic materials under awide range of climatic conditions and include seven
great groups (Table 3). Aquands occur in the PacificNorthwest of the United States and in other areas thathave volcanic influence (Soil Survey Staff, 1999).
Cryaquands are extensive in Alaska and Melanaquands characteristically occur in the lowlands ofJapan (Shoji and Ping, 1992).
Cryands: Cryands are defined as Andisols having a
cryic or pergelic soil temperature regime (Soil Survey
Staff, 1999). There are six great groups within the
Cryand suborder (Table 3).
The classification criteria for Cryands were developed mainly according to the studies on Andisols in
Alaska and in the high mountains of northeasternJapan (Ping et al., 1988, 1989; Shoji et al., 1988a,
1988b). Cryands have formed in the western part ofNorth America and the northeastern part of Asia above
49 degrees north latitude and in mountains south ofthat latitude. Most of the soils have formed under
Table 3

Suborders and great groups in Soil Taxonomy(Soil Survey Staff, 1999).

SuborderAquands

Great group
Cryaquands
Placaquands
Duraquands
Vitraquands
Melanaquands
Epiaquands
Endoaquands

Cryands

Duricryands
Hydrocryands
Melanocryands
Fulvicryands
Vitricryands
Haplocryands

Torrands

Duritorrands
Vitritorrands
Haplotrrands

Xerands

Vitrixerands
Melanoxerands
Haploxerands

Vitrands

Ustivitrands
Udivitrands

Ustands

Durustands
Haplustands

UdandsPlacudands
Durudands
Melanudands
Hydrudands
Fulvudands
Hapludands

87

coniferous forest vegetation (Soil Survey Staff, 1999).
Cryands and Spodosols such as Haplocryods,
Humicryods, and Placocryods have commonly developed in the same parent materials under a cryic soil
temperature regime. They share a number of important physical and chemical properties (Shoji and
Ito, 1990; Takahashi, 1990). In the present Soil
Taxonomy (Soil Survey Staff, 1999), tephra-derived
Spodosols satisfying the albic and spodic requirements are classified as Spodosols even if they meetrequirement of andic soil properties. In some multisequum Andisols, C horizons or light-colored ash
layers in upper profiles can be easily confused with an
albic horizon (Ito et al., 1991). If the C horizon of anAndisol showing a horizon sequence of
A-C-2Ab-2Bwb is misidentified as an albic horizon,
the 2Ab horizon (buried humus horizon) could be
regarded as a spodic horizon. Thus, careful fieldobservation of soil profiles is necessary todifferentiate a spodic horizon from a buried A horizon.
Torrands: Torrands are Andisols that have an
aridic moisture regime (Soil Survey Staff, 1999).
Even though tephra is dominated by volcanic glass,which is the most weatherable component in tephra,
the rate of its chemical weathering is restricted under
dry conditions. Torrands formed in the western partof North America, and some are known to occur in
Hawaii and other Pacific islands (Soil Survey Staff,
1999).
Xerands: Xerands are Andisols that have a xeric
moisture regime (Soil Survey Staff, 1999). Xerands
includes three great groups of vitric, melanic andhaplic (Table 3). It is interesting to note that thefulvic great group is not provided in spite of thepresence of Melanoxerands. This suggests that humification of organic matter is favorable under a xeric
soil moisture regime resulting in formation of melanic
epipedons even in forest vegetations as observed in
California, United States (Takahashi et al., 1995).
Vitrands: Vitrands are Andisols that have 1500 kPa
water retention of less than 15% in air-dried samples
and less than 30% in undried samples throughout 60%
or more of the thickness (Soil Survey Staff, 1999).
The parent material of Vitrands is commonly pumice,cinder, or scoria, and is weakly weathered. Because
the Vitrands suborder is keyed out before thesuborders of Ustands and Udands, vitric great groups
are not provided in these suborders.
Ustands: Ustands are Andisols that have an ustic
soil moisture regime (Soil Survey Staff, 1999). They
include two great groups: duric and haplic. They
occur mostly in Mexico, the western part of theUnited States, the Pacific Islands, and the eastern partof Africa. Most Ustands in the United States are in
Hawaii, Arizona, and New Mexico (Soil Survey Staff,
1999).
Udands: Udands are Andisols that have a udic soil
moisture regime and are the Andisols most widelyused for agriculture. They are largely found on the

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T. TAKAHASHI and S. SHOJI

Pacific Rim, mainly in the western part of North
America and Japan, New Zealand, the Philippines,
and Indonesia (Soil Survey Staff, 1999). Since theyoccur in humid temperate to humid tropic zones, theirweathering rates are great, forming an abundance ofshort-range-order minerals. Six great groups are provided for Udands: placic, duric, melanic, hydric,fulvic, and haplic (Table 3).
Melanudands and Fulvudands attracted muchattention during the examination process of Andisol
classification. The traditional concept of Kurobokudo (Andosols) in Japan is soils having a black
humus-rich horizon and friable consistency (Fig. 5(b)). The central concept of melanic Andisols described by Smith (1978) originated from such a humus
horizon that has the primary characteristics of Kurobokudo (The Third Division of Soils, 1982).
In order to establish a definition of melanic epipedons and to separate exactly melanic and fulvic
Andisols, requirements for depth, organic carbon
content, and soil color of melanic epipedons were
proposed by Shoji (1988).
The melanic index
needed for soil color requirements was established by
Honna et al. (1988). It indicates an abundance oftype A humic acid in the soil organic matter that is
attributable to the very dark color. The final definition of the melanic epipedon in the current Soil Taxonomy is shown in Table 4. Melanudands are extensively formed in Japanese pampas grass (Miscanthus
sinensis) and Sasa ecosystems in Japan.
Fulvudands are Udands with thick dark brown
epipedons with high contents of organic matter thatare not as dark as melanic epipedons (Fig 5 (c)).
Although the two great groups have thick, highorganic matter content horizons, they differ remarkably in the characteristics of their humus. Fulvudands
show high fulvic acid to humic acid ratios andcommonly have organic matter with melanic indiceshigher than 1.70 (Honna et al., 1988).
Each great group is further divided into subgroups.
For example, Melanudands have 15 subgroups andHapludands, 20 subgroups. Several subgroups are
selected for discussion as follows.
Alic subgroups: Alic Andisols have 1 M
KCl-extractable Al of more than 2.0 cmolc kg–1 in the
Table 4fine-earth fraction throughout a layer 10 cm or more
thick between a depth of 25 and 50 cm (Soil Survey
Staff, 1999). This level of exchangeable Al ispotentially toxic enough to severely reduce the root
growth of Al-sensitive plants (Saigusa et al., 1980).
The layer underlying the Ap or surface horizon (25 to
50 cm) is employed to determine the level ofexchangeable Al because its soil properties are little
affected by farming practices.
Aquic and anthraquic subgroups: The aquic
subgroups are identified by the presence of aquicfeatures in some subhorizon between 50 to 100 cm
from the mineral soil surface or from the upperboundary of an organic layer with andic soil properties.
On the other hand, well drained to excessively drained
Andisols exhibit changed properties after puddling of
surface soil and continuous flooding for rice cultivation. Changes include degradation of soil structure,development of a plowpan, loss of iron and manganese from the Ap horizon, and accumulation of ironand manganese (mottles and nodules) in the subsurface horizon. These features are characteristic of theanthraquic subgroup designation.
Pachic subgroups: Pachic subgroups of Andisols
have more than 6.0% organic carbon and meet thecolor requirements of the mollic epipedon throughout
at least 50 cm of the upper 60 cm, excluding any
overlying layers that do not have andic soil properties(Soil Survey Staff, 1999). Since the range of molliccolors includes the color requirements for bothmelanic epipedons and fulvic surface horizons, thepachic subgroups are Andisols with thick melanic
epipedons or fulvic surface horizons.
Thaptic subgroups: Many Andisols have a multisequum profile, reflecting repeated tephra depositionand subsequent soil formation. Thaptic subgroups ofAndisols are defined as soils that have, at depths between 25 and 100 cm (between 40 and 100 cm formelanic and fulvic great groups) from either themineral soil surface or the top of an organic layer with
andic soil properties, whichever is shallower, a layer
10 cm or more thick with more than 3.0% organiccarbon and colors of a mollic epipedon throughout,underlying one or more horizons with a total thicknessof 10 cm or more that have a color value, moist, 1 unit

Definition of melanic epipedon in Soil Taxonomy (Soil Survey Staff, 1999).

The melanic epipedon has both of the following:
1.

An upper boundary at, or within 30 cm of, either the mineral soil surface or the upper boundary of an organic
layer with andic soil properties, whichever is shallower; and2.

In layers with a cumulative thickness of 30 cm or more within a total thickness of 40 cm, all of the following:a. Andic soil properties throughout; andb. A color value, moist, and chroma (Munsell designations) of 2 or less throughout and a melanic index of 1.70 orless throughout; andc. 6% or more organic carbon as a weighted average and 4% or more organic carbon in all layers.

Distribution and Classification of Volcanic Ash Soils

or more higher and an organic-carbon content 1% ormore (absolute) lower (Soil Survey Staff, 1999).

4. Classification of Andosols in the World
Reference Base for Soil Resources (WRB)
The Andosol major soil grouping was created by
FAO/Unesco (1974) in order to prepare its Soil Mapof the World. The definition of this grouping was
drawn from that of the Andept suborder in Soil
Taxonomy (Soil Survey Staff, 1975). FAO/Unesco(1988) revised the classification of Andosols by introducing andic soil properties criteria. In recent years,
FAO, the International Soil Reference and Information
Centre (ISRIC), and the International Society of Soil
Science (ISSS) published the World Reference Basefor Soil Resources (WRB) (1998). No differentiae
comparable to the family and series differentiae inSoil Taxonomy are provided for further classificationof Andosols.
The definition of the Andosol reference soil groupin the WRB Classification is based on the existence ofa vitric or an andic horizon that starts within 25 cm
from the soil surface (Table 5). They should have nodiagnostic horizons (unless buried deeper than 50 cm)
other than a histic, fulvic, melanic, mollic, umbric,ochric, duric or cambic horizon (Table 5). Andosols
are keyed out after Gleysols and before Podzols.
Although Podzols are keyed out after Andosols inthis system, Podzols derived from volcanic materials
are recognized. According to item 2 of the definitionof Andosols (Table 5), the soils satisfying albic or

89

spodic horizon criteria are excluded from Andosols
even if they have vitric or andic horizons, and they areclassified as Podzols.
Diagnostic criteria of the andic horizon and vitrichorizon shown in Table 5 are comparable to criterion
1 and criterion 2, respectively, of andic soil properties
in Soil Taxonomy. In order to improve Andosolclassification in the WRB system, a generalized
relationship between Regosols and three types ofAndosols is proposed by Shoji et al. (1996) as
presented in Fig. 3. Two major types of andic horizons are introduced: the sil-andic type and alu-andic
type. The sil-andic type is an andic horizon in whichallophane and similar minerals are predominant. The
alu-andic type is one in which aluminum complexedby soil organic matter prevails, being regarded as anonallophanic Andosol.
The existence and properties of the alu-andic typeor nonallophanic Andosols were first reported by
Shoji and Ono (1978).
They showed thataluminum-humus complexes also contribute to manyof the unique properties common to allophanic(sil-andic) Andosols: high water-holding capacity,
high phosphate retention, low bulk density, and highfriability. In contrast to the sil-andic (allophanic)
Andosols, however, most nonallophanic Andosols
show very strong acidity (pH < 5.0), high Al
saturation and Al toxicity to plants. Nonallophanic
volcanic ash soils account for about 30% of all
volcanic ash soils in Japan (Fig. 2) (Saigusa andMatsuyama, 1998) and are mostly used for growing
upland crops.

Table 5 Definition of Andosol reference soil group and diagnostic criteria for andic and vitric horizons in the WRBClassification (FAO et al., 1998).
Other soils having
1. either a vitric or an andic horizon staring within 25 cm from the soil surface; and2. having no diagnostic horizons (unless buried deeper than 50 cm) other than a histic, fulvic, melanic, mollic, umbric,ochric, duric or cambic horizon.
ANDOSOLS (AN)Diagnostic criteria for Andic horizon. An andic horizon must have the following physical, chemical andmineralogical properties:
1. bulk density of the soil at field capacity (no prior drying) of less than 0.9 kg dm-3; and2. 10% or more clay and an Alox + 1/2 Feox* value in the fine earth fraction of 2% or more; and3. phosphate retention of 70% or more; and4. volcanic glass content in the fine earth fraction of less than 10%; and5. thickness of at least 30 cm.
Sil-andic horizons have an acid oxalate (pH 3) extractable silica (Siox) of 0.6% or more while alu-andic
horizons have a Siox of less than 0.6% (or, alternatively, Alpy/Alox ratio of less than 0.5 and 0.5 or more,
respectively).
Diagnostic criteria for Vitric horizon. A vitric horizon must have:
1. 10% or more volcanic glass and other primary minerals in the fine earth fraction; and either:
2. less than 10% clay in the fine earth fraction; or
3. a bulk density > 0.9 kg dm-3; or
4. Alox + 1/2 Feox* > 0.4%; or
5. phosphate retention > 25%; and6. thickness of at least 30 cm.
* Alox and Feox are acid oxalate (pH 3) extractable aluminium and iron, respectively (method of Blakemore et al.,1987).

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T. TAKAHASHI and S. SHOJI

Regosols
0.4%

Alo + 1/2Feo25%

Vitr-andic

70%

1.2%

Sil-andic0

P ret.

Alu-andic
0.5

1

Alp/AloFig. 3 The generalized relationship between Regosols and the three subtypes of Andosols in WRB
classification (Shoji et al., 1996).

Table 6 Priority listing of lower-level units of Andosols in the WRB Classification (FAO et al., 1998).
Vitric:having a vitric horizon within 100 cm from the soil surface and lacking an andic horizon overlying
a vitric horizon.
Eutrisilic: having a sil-andic horizon and a sum of exchangeable bases of 25 cmolc kg-1 fine earth within
30 cm from the soil surface.
Silic:
having an andic horizon with an acid oxalate (pH 3) extractable silica (Siox) content of 0.6% or
more, or an Alpy/Alox ratio less than 0.5.
Gleyic:having gleyic properties within 100 cm from the soil surface.
Melanic: having a melanic horizon.
Fulvic:having a fulvic horizon within 30 cm from the soil surface.
Hydric: having within 100 cm from the soil surface one or more layers with a total thickness of 35 cm or
more, which have a water retention at 1500 kPa (in undried samples) of 100% or more.
Pachic:having a mollic or umbric horizon of more than 50 cm thick.
Histic:having a histic horizon within 40 cm from the soil surface.
Mollic:having a mollic horizon.
Duric:
having a duric horizon within 100 cm from the soil surface.
Umbric: having an umbric horizon.
Luvic:
having an argic horizon which has a cation exchange capacity equal to or more than 24 cmolc kg-1
clay throughout, and a base saturation by 1 M NH4OAc of 50% or more throughout the horizon toa depth of 100 cm from the soil surface.
Placic:having within 100 cm from the soil surface a subhorizon of the spodic horizon which is 1 cm or
more thick and which is continuously cemented by a combination of organic matter and aluminium,
with or without iron (“thin iron pan”).
Leptic:having continuous hard rock between 25 and 100 cm from the soil surface.
Acroxic: having less than 2 cmolc kg-1 fine earth exchangeable bases plus 1 M KCl exchangeable Al 3+ in one
or more horizons with a combined thickness of 30 cm or more within 100 cm from the soil surface.
Vetic:
having less than 6 cmolc kg-1 clay of exchangeable bases plus exchangeable acidity in at least somesubhorizon of the B horizon within 100 cm from the soil surface.
Calcaric: calcareous at least between 20 and 50 cm from the soil surface.
Arenic:having a texture of loamy fine sand or coarser throughout the upper 50 cm of the soil.
Sodic:
having more than 15% exchangeable sodium or more than 50% exchangeable sodium andmagnesium on the exchange complex within 50 cm from the soil surface.
Skeletic: having between 40 and 90% (by weight) gravel or other coarse fragments to a depth of 100 cm
from the soil surface.
Thaptic: having a buried horizon within 100 cm from the soil surface.
Dystric: having a base saturation (by 1 M NH4OAc) of less than 50% in at least some part between 20 to
100 cm from the soil surface.
Eutric:having a base saturation (by 1 M NH4OAc) of 50% or more at least between 20 and 100 cm fromthe soil surface.
Haplic:other Andosols.

Distribution and Classification of Volcanic Ash Soils

5. Classification of Volcanic Ash Soils inJapan
Three national soil classification systems, i.e., theJapanese Cultivated Soil Classification (Cultivated
Soil Classification Committee, 1994), the Classification of Forest Soils (Forest Soil Division, 1976) andthe Soil Classification for Land Classification Surveys(National Land Survey Division, 1969) have been employed according to the purposes of soil classification.
Recently, the Japanese Society of Pedology organizeda Committee for Soil Classification and Nomenclature
to prepare a “Unified Soil Classification System ofJapan.” Among them, the Japanese Cultivated Soil
Classification has the most comprehensive system for
Kurobokudo or volcanic ash soils as shown in Table 7.
Volcanic ash soils are identified in the soil groups ofVolcanogenous Regosols, Gleyed Andosols (Gleyed
Kurobokudo), Wet Andosols (Wet Kurobokudo),
Forest Andosols (Forest Kurobokudo), Non-allophanic
Andosols (Non-allophanic Kurobokudo) and Andosols(Kurobokudo). Compared with the previous classification (The Third Division of Soils, 1982), the current

50

Percentage of pedons, %

40
30
20
10

Hydric

FulvicMelanic

GleyicSilic

Eutrisilic0
VitricIn the WRB system, qualifiers are used for
subdivisions of reference soil groups, and theirpriority sequence for the Andosols reference soil
group is shown in Table 6. The first priority is given
to Vitric Andosols having a vitric horizon within 100
cm from the soil surface and lacking an andic horizon
overlying a vitric horizon. The second priority isprovided to sil-andic properties (Eutrisilic and Silic)followed by Gleyic, Melanic, Fulvic, etc.
As previously done by Shoji et al. (1996), the
WRB Classification was evaluated using the Tohoku
University World Andosol Database (TUWAD). For
this purpose, seven basically important lower-level
units were selected and their percentage distribution
was determined as shown in Fig. 4. 22% of the soils
in TUWAD were classified as Vitric Andosols. 45%
met the requirement of the Silic unit, which included
soils with Eutrosilic properties. In the diagnostic
criteria of andic horizons (Table 5), both sil-andic andalu-andic horizons are described for exact differentiation. However, alu-andic horizons are not reflectedin the WRB system so that the percentage distribution
using TUWAD lacks alu-andic Andosols (Fig. 4).
Furthermore, although TUWAD includes many
Melanic Andosols and Fulvic Andosols, the percentage distribution shows 19% of Andosols meeting themelanic requirement while there are no Andosols
satisfying the fulvic requirement (Fig. 4). In addition,
the requirements for Luvic, Vetic and Arenic Andosols
need mechanical analyses. However, their accurate
determination is often difficult due to incomplete dispersion of mineral particles and uncertainty of unit
mineral particles (Nanzyo et. al., 1993). These facts
indicate the necessity of revising the Andosol classification of the WRB system.

91

Fig. 4 Percentage distribution of 7 soil units of volcanic ash
soils using data from Tohoku University World
Andosol Database (TUWAD).

classification additionally includes Forest Andosols
and Non-allophanic Andosols. The central conceptof Andosol (Kurobokudo) groups is soils that havedeveloped in pyroclastic materials and are characterized by high phosphate adsorption coefficients, lowbulk densities, and high fluffiness. Each soil subgroup is defined mainly based on occurrences ofhumus horizons and organic matter contents that arethought to be the most important for soil productivity.
Volcanogenous Regosols are defined as soils having a 25 cm or more thick soil layer whose phosphateadsorption coefficient is less than 1500 mg/100g (85%
P retention) within 50 cm from the soil surface and arecorrelated with Vitrands in Soil Taxonomy and VitricAndosols in the WRB Classification. This soil group
has three subgroups: 1) an Aquic subgroup having agleyed layer or water-table within 50 cm from the soil
surface, 2) a Humic subgroup having humic or
high-humic surface horizons, and 3) a Haplic
subgroup.
Gleyed Andosols (Gleyed Kurobokudo) are hydromorphic Andosols that have developed under permanently or nearly permanently water-saturated conditions and are characterized by the occurrence of a gley
horizon or upper boundary of an organic layer within
50 cm from the soil surface. They correspond to the
Aquands suborder in Soil Taxonomy (Soil Survey
Staff, 1999). Gleyed Andosols are mainly distributed
in lowlands and valley floors, and are used mostly as
paddy rice fields. Gleyed Andosols are divided into
three subgroups: Peaty Gleyed Andosols having anorganic layer within 50 cm from the soil surface,
Cumulic Gleyed Andosols having thick (> 50 cm)
humic or high humic surface horizons, and Haplic
Gleyed Andosols.
Wet Andosols (Wet Kurobokudo) are defined as
Andosols having an upper boundary of an iron mottle
layer or a grey layer with mottling within 50 cm from

92

T. TAKAHASHI and S. SHOJI
Table 7 Classification of volcanic ash soils in the Classification of Cultivated Soils in Japan(The Third Approximation) (Cultivated Soil Classification Committee, 1994).
Soil Groups

Soil Subgroups

Volcanogenous Regosols

Aquic Volcanogenous Regosols
Humic Volcanogenous Regosols
Haplic Volcanogenous Regosols

Gleyed Andosols

Peaty Gleyed Andosols
Cumulic Gleyed Andosols
Haplic Gleyed Andosols

Wet Andosols

Thapto-upland Wet Andosols
Thapto-lowland Wet Andosols
Cumulic Wet Andosols
Haplic Wet Andosols

Forest Andosols

Haplic Forest Andosols

Non-allophanic Andosols

Anthraquic Non-allophanic Andosols
Cumulic Non-allophanic Andosols
Haplic Non-allophanic Andosols

Andosols

Anthraquic Andosols
Thapto-upland Andosols
Thapto-lowland Andosols
Low-humic Andosols
Cumulic Andosols
Haplic Andosols

the soil surface. These characteristics develop mainly under the influence of irrigation for rice cultivationand other uses due to penetration by groundwater or
stagnant water. They are extensively distributed inalluvial lowlands, valley floors and uplands with poor
permeability and are used largely for paddy rice, andpartly for upland crops and grasses. Wet Andosols
are divided into four subgroups: Thapto-upland Wet
Andosols having the upper boundary of a buried
upland soil within 50 cm from the soil surface,
Thapto-lowland Wet Andosols having the upperboundary of a buried lowland soil within 50 cm fromthe soil surface, Cumulic Wet Andosols having thick(> 50 cm) humic or high humic surface horizons, andHaplic Wet Andosols.
Forest Andosols (Forest Kurobokudo) are definedas Andosols having surface horizons with organic
matter of 10% or more and soil color other than black(hue/chroma 1.7/1, 2/1, 2/2) and correspond to
Fulvudands in Soil Taxonomy. Volcanic ash soils innatural forests generally do not show a black color
though they contain high amounts of organic matter.
Forest Andosols typically develop under beech (Fagus
crenata) forests.
Non-allophanic Andosols (Non-allophanic Kurobokudo) are Andosols showing a predominance ofAl-humus complexes in the colloidal fraction, andstrong acidity and high exchangeable acidity
attributable to 2:1 layer silicates. They are definedas the soils having subsurface horizons withexchangeable acidity Y1 of 5 or more.
Non-allophanic Andosols correspond to the alu-andic
Andosols in the WRB Classification. Although they

possess properties such as low bulk densities, highphosphate retention, etc., which are common toallophanic Andosols, they have a high potential foraluminum toxicity to plant roots. Non-allophanic
Andosols are divided into three subgroups: theAnthraquic subgroup having illuvial horizons due topaddy farming, the Cumulic subgroup having thick(> 50 cm) humic or high humic surface horizons, andthe Haplic subgroup.
The other volcanic ash soils which do not meet therequirements of the five soil groups described above
are classified as Andosols (Kurobokudo). Andosols(Kurobokudo) are soils that have developed under welldrained conditions and show a clay mineralogy
dominated by allophane and imogolite and have highaccumulations of soil organic matter. They have characteristics such as high phosphate retention, low bulk
densities, high organic matter content, and the presence of highly humidified humic acid. They aremostly used as upland crop fields, pastures, orchards,
tea gardens, etc. Andosols (Kurobokudo) are divided
into six subgroups: Anthraquic, Thapto-upland,
Thapto-lowland, Low-humic, Cumulic and Haplic.

6. Classification of Volcanic Ash Soils in
New Zealand Soil Classification
The New Zealand Soil Classification, the sole
national soil classification in New Zealand wasderived from the New Zealand Genetic Soil
Classification (Taylor, 1948; Taylor and Cox, 1956;
Taylor and Pohlen, 1962) preserving successful partsof that classification. The present version (Version

Distribution and Classification of Volcanic Ash Soils

3.0) (Hewitt, 1998) was published after extensive
testing of versions 1.0 and 2.0 (Hewitt, 1989). In
this classification system, as presented in Table 8,
volcanic ash soils are identified in the soil orders ofallophanic Soils, Pumice Soils, Granular Soils, andRecent Soils.
Allophanic Soils are keyed out after Podzols anddefined as soils that have a layer or layers of allophanic soil material that total 35 cm or more in
thickness and occur within 60 cm of the mineral soil
surface. The definition of allophanic soil materials isbased on the presence of not only allophane but also
imogolite and ferrihydrite.
Allophanic Soils are divided into four groups
according to water permeability and characteristics
associated with wetness. Each group is further divided into several subgroups (Table 8).
Pumice Soils are keyed out after allophanic Soils
and are soils that have both
1. a layer of vitric soil material existing from themineral soil surface to 25 cm or deeper, or are 35 cm
or more thick occurring within 60 cm of the mineralsoil surface, and
2. a weathered-B horizon 5 cm or more thick.
They are mostly correlated with the Vitrands,
Vitraquands and Vitricryands of Soil Taxonomy (SoilSurvey Staff, 1999). Pumice soils have properties
dominated by a pumiceous and glassy skeleton withlow clay content which typically contains allophane.
They occur in sandy or pumiceous tephra ranging
from 700 to 3,500 years in age in New Zealand(Hewitt, 1998). Pumice Soils are divided into threegroups and each group is divided into several subgroups (Table 8).
Granular Soils are derived predominantly fromstrongly weathered tephras mostly older than 50,000
years (Hewitt, 1998). They contrast with allophanic
and Pumice Soils by having clay mineralogy dominated by kaolin-group minerals and associated vermiculite and hydrous-interlayered vermiculite. Some
Granular Soils are derived also from basaltic and93

andesitic rocks with possible addition of aeolianmaterial (Hewitt, 1998).
Most Granular Soils are correlated with Ultisols
but a few with the Alfisols of Soil Taxonomy. They
are divided into four groups and each group into
several subgroups (Table 8).
Volcanic ash soils belonging to Recent Soils are
identified in the Tephric group that have developed intephra deposits from the mineral soil surface to adepth of 30 cm or more. The group is divided into
four subgroups (Table 8).

7. Correlation of International andDomestic Systems
As mentioned earlier, each national soil classification system organizes knowledge of the distribution,
properties, productivity, utilization, and managementof soils in its respective jurisdiction. As for the international systems, they are not a substitute for nationalsoil classification systems, but should be a tool forcorrelation between national systems. This is one of
the main objectives of the WRB Classification (FAO
et al., 1998). It is desirable that both the national andinternational systems be well harmonized with eachother. In this section, six pedons with color picturesare selected as examples to study their correlation
with Soil Taxonomy, the WRB Classification, and theJapanese Cultivated Soil Classification.
Bekkai soil: The Bekkai soil from eastern
Hokkaido, Japan (Fig. 5 (a) on page 95) is one of therepresentative vitric soils. It has formed from intermittently deposited rhyolitic ash layers ranging in age
from a few hundred to less than 1,000 years old underudic soil moisture and frigid soil temperature regimes.
The pedon has a multisequum profile consisting of
A-C horizons overlying four A-Bw-C horizon
sequences and shows a low degree of weathering,
especially in the upper part of the profile.
According to characterization data for selected

Table 8 Classification of volcanic ash soils in the New Zealand system (Version 3.0) (Hewitt, 1998).
Order

Group

Subgroup

Allophanic Soils

Perch-gley
Gley
ImpededOrthicIronstone, Typic
Peaty, Typic
Mottled-ironstone, Mottled, Typic
Mottled, Vitric-acidic, Vitric, Acidic, Typic

Pumice Soils

Perch-gley
ImpededOrthicDuric, Typic
Mottled-welded, Welded, Mottled, Typic
Mottled, Podzolic, Allophanic, Buried-allophanic,
Immature, Typic

Granular Soils

Perch-gley
Melanic
OxidicOrthicOxidic, Acidic, Typic
Mottled, Allophanic, Typic
Mottled-acidic, Mottled, Allophanic, Acidic, Typic
Mottled-acidic, Mottled, Allophanic, Acidic, Typic

Recent Soils*

Tephric

Mottled, Buried-pumice, Buried-allophane, Typic*Soils derived from volcaniclastic materials are extracted.

94

T. TAKAHASHI and S. SHOJI

horizons of the Bekkai soil (Shoji et al., 1993), theupper horizons (0 – 48 cm) show a high content of
volcanic glass (95 – 97%) and low values for clay
content (< 6%), acid oxalate-extractable components(Alo + 1/2 Feo = 0.8 – 1.6%), and P retention (33 –66%). The acid oxalate-extractable components andP retention tend to increase with depth. Bulk densities are somewhat high and water retention values at
1500 kPa are mostly low.
According to vitric properties and multisequum
profile, the Bekkai soil is classified as a Thaptic
Udivitrand in Soil Taxonomy, a Thapto-Vitric Andosolin the WRB Classification, and a Haplic
Volcanogenous Regosol in Japanese Cultivated Soils
Classification (Table 9).
Mukaiyama soil: Mukaiyama is a forestland on
the Tohoku University Farm, Miyagi Prefecture,northeastern Japan and was selected as the type
locality for nonallophanic Andisols by M. Leamy,
Chairman of the International Committee on theClassification of Andisols. The volcanic ash soil of
this area (Fig. 5 (b)) has a distinct morphologicalfeature of a very dark (color value and chroma of 2 orless), thick humus horizon (0 – 57 cm) formed fromcumulative ash of 10,000 to 1,000 yr B. P. andprominent properties attributable to the predominanceof 2:1 layer silicates and Al-humus complexes.
The characterization data of the Mukaiyama soil
(Shoji et al., 1993) show that the humus horizons havean organic carbon concentration greater than 6.0%, a
predominance of A-type humic acid, and a melanic
index less than 1.70 in the humus horizons (0 –57 cm). Thus, it meets not only melanic epipedon
requirements but also the pachic subgroup requirement for Andisols in Soil Taxonomy. The humus
horizons possess extremely high KCl-extractable Alvalues (8 – 11 cmolc kg–1) and show high Alp/Alo ratios
indicating predominance of Al-humus complexes.

Accordingly, the allophanic materials icontent in thesehorizons is very low.
According to the properties described above, theMukaiyama soil is classified as a high-humic Cumulic
Non-allophanic Andosol by the Japanese Cultivated
Soil Classification, and was classified as an Alic
Pachic Melanudand in the 1992 Keys to Soil Taxonomy (Shoji et al., 1993), showing a nonallophanic
Udand with presence of a very dark thick humus
horizon and high potential of Al toxicity to plant roots.
However, it is classified as a Pachic Melanudand by
the last Key to Soil Taxonomy (Soil Survey Staff,
1998) because the alic subgroup is not provided for
Melanudands. While the WRB Classification has thedefinitions of both alu-andic and sil-andic types (FAO
et al., 1998), the Mukaiyama soil is classified as a
Dystri-Melanic Andosol, indicating that this soil
belongs to neither alu-andic nor sil-andic Andosols.
These facts show the necessity of partly revising theclassification of Andisols and Andosols.
Yunodai soil: The Yunodai soil (Fig. 1 on page 72)
from the Towada district, Aomori Prefecture, Japan
also has very dark (color value and chroma of 2 orless) and thick humus horizons (0 – 60 cm) formed
from Towada-a ash of 1,000 yr. B. P. (0 – 30 cm) andChuseri ash of 5,000 yr. B. P. (30 – 79 cm) under the
influence of Japanese pampass grass (Miscanthus
sinensis) vegetation. According to the characterization data (Shoji et al., 1988b), this pedon has humus
horizons that meet the melanic epipedon requirement
and has exchangeable bases plus 1 M KCl extractable
Al totaling less than 2.0 cmolc kg-1 in horizons withtotal thickness of 30 cm or more between 25 and100 cm depth. It shows low 1500 kPa water retention (< 15% on air dried and < 30% on undriedsamples) in horizons having 25 cm or more thick.
Thus, this pedon is classified as an Acrudoxic Vitric
Melanudand in Soil Taxonomy (Table 9). It has

Table 9 Classification of selected pedons according to Soil Taxonomy, WRB Classification, and Japanese
Cultivated Soil Classification.
Soil Taxonomy

WRB Classification

Cultivated Soil
Classification

Bekkai(Fig. 5 (a) on page 95)

ashy over medial, frigid
Thaptic Udivitrand

Thapto-Vitric Andosol(Dystric)

ashy typic Haplic
Volcanogenous Regosol

Mukaiyama(Fig. 5 (b) on page 95)

medial, mesic Pachic
Melanudand

Dystri-Melanic Andosol

high-humic Cumulic
Non-allophanic Andosol

Yunodai(Fig. 1 on page 72)

medial over cindery,
mesic Acrudoxic Vitric
Melanudand

Melani-Silic Andosol(Acroxic)

high-humic Cumulic
Andosol

Tsutanuma(Fig. 5 (c) on page 95)

medial over cindery,
mesic Acrudoxic
Fulvudand

Umbri-Silic Andosol(Acroxic)

Haplic Forest Andosol

Hilo(Fig. 1 on page 72)hydrous, isohyperthermic
Acrudoxic Hydrudand

Hydri-Silic Andosol(Acroxic)

Haplic Andosol

Findley Lake
(Fig. 1 on page 72)

frigid Andic Humicryod

Haplic Podzol

Haplic Podzol

Distribution and Classification of Volcanic Ash Soils

sil-andic properties in horizons derived from Chuseri
ash, so it is classified as a Melani-Silic Andosol
according to the WRB Classification. Based on thepresence of the thick, dark humus horizons, theYunodai soil is classified as a high humic Cumulic
Andosol in Japanese Cultivated Soil Classification(Table 9).

Tsutanuma soil: The Tsutanuma soil (Fig. 5 (c) on
page 95) from the Towada district adjoins the Yunodai
soil and is an example of a fulvic volcanic ash soil.
The pedon also shows composite morphology formed
from the same cumulative tephra as those of the
Yunodai soil and has a thick cumulative humus
horizon (0 – 48 cm). However, it fails the melaniccolor requirement of moist Munsell value and chroma(a) Bekkai soil.

(b) Mukaiyama soil.

95(c) Tsutanuma soil.

Fig. 5 Selected soil profiles for testing soil classifications (Shoji et al., 1993; copyright Elsevier, with permission).

96

T. TAKAHASHI and S. SHOJI

of 2 or less (Soil Survey Staff, 1999) reflecting theinfluence of beech tree (Fagus crenata) vegetation.
It has irregular boundaries between the 2AB2 and
2Bwb horizons and a broken boundary between the
2Bwb and 3C horizons. These boundaries reflect theprocess of tree-fall which results in mixing of the soilmaterials between soil horizons.
The characterization data for the Tsutanuma soil
(Shoji et al., 1993) show that the humus horizons do
not have a very dark color. But soil organic carbon
has markedly accumulated in the upper part of the soil
profile with more than 6% as a weighted average at
depths of 0 – 30 cm (Shoji et al., 1993). Thesehorizons had melanic indices greater than 1.70 andlow ratios of humic acid to fulvic acid.
According to the profile description and characterization data, the Tsutanuma soil is classified as a
Fulvudand by Soil Taxonomy and as a Forest Andosol
by Japanese Cultivated Soil Classification (Table 9).
However, the pedon does not satisfy the definition offulvic horizons described in the WRB Classification
because the fulvic horizon in the WRB Classification
requires a Munsell color value and chroma of 2 or less
(FAO et al., 1998). This color requirement is thesame as that of the melanic color requirement in Soil
Taxonomy (Table 4) showing a very dark color, so it
should be revised.
Hilo soil: Hydric volcanic ash soils occur inregions of very high, well-distributed rainfall with aperudic moisture regime (Soil Survey Staff, 1975).
They show high water retention capacities such as1500 kPa water retention of more than 100% and 33
kPa water retention of several hundred percent.
The Hilo soil (Fig. 1 on page 72) from Hawaii,
U.S.A., is an example of a hydric volcanic ash soil.
It has very thick B horizons with dark reddish to
reddish brown color and moderate to strong thixotropy.
According to the characterization data of the Hilo soil
(Shoji et al., 1993), the pedon shows very low bulk
densities (< 0.5 g cm–3) and 1500 kPa water retentionof greater than 100%. The sum of exchangeablebases is very small in amount (mostly about
1 cmolc kg–1) reflecting intense base leaching. In
spite of the low base saturation, all the horizons show
only slight acidity, due to allophanic clay mineralogy
and mostly possess exchangeable bases plus 1 M KCl
extractable Al totaling less than 2.0 cmolc kg–1. Thus,
the Hilo soil is classified as an Acrudoxic Hydrudandin Soil Taxonomy (Table 9). Since most horizons
have acid oxalate extractable Si of 0.6% or more, thispedon is classified as a Hydri-Silic Andosol in the
WRB Classification (Table 9).
Findley Lake soil: The Findley Lake soil (Fig. 1,
on page 72) from Cascade Range, Washington, U.S.A.
is an example of podzolic volcanic ash soils. In Soil
Taxonomy, tephra-derived podzolic soils satisfying the
albic and spodic requirements are classified as

Spodosols (Soil Survey Staff, 1999). Since theFindley Lake soil meets these requirements (Dahlgren
and Ugolini, 1989), it is identified as a Spodosol.
The pedon has a cryic soil temperature regime andshows high organic carbon content (≥ 6.0%) in a layer
10 cm or more thick within the spodic horizons. It
also shows andic soil properties throughout the spodic
horizons and the underlying BC and C horizons(Dahlgren and Ugolini, 1989).
Therefore, theFindley Lake soil is classified as an Andic Humicryodin Soil Taxonomy (Table 9). This pedon is classified
as a Haplic Podzol both in the WRB Classificationand the Japanese Cultivated Soil Classification(Table 9) because these two classification systems do
not have any andic subdivisions for Podzols.
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(Received 2 September 2002, Accepted 10 October 2002)