The document discusses soil taxonomy and the US comprehensive soil classification system. It describes the hierarchical structure of the classification system, which categorizes soils into orders, suborders, great groups, subgroups, families, and series based on distinguishing characteristics like soil properties and diagnostic horizons. The key diagnostic horizons used in classification include epipedons (surface horizons) like the mollic and spodic horizons, and endopedons (subsurface horizons) like the argillic, calcic, and oxic horizons. Major soil orders discussed are Mollisols, Alfisols, Ultisols, Entisols, Inceptisols, and Spodosols.

1. SOIL SCIENCE
FPT 2093
Lecture Week 10:
Soil Taxonomy
En Mohd Fauzie Jusoh
Lecturer
Agrotechnology Programme
Faculty of Agro-Based Industry
Universiti Malaysia Kelantan (Jeli Campus)
Locked Bag No.100, 17600 Jeli, Kelantan.
014-2903025/fauzie.j@umk.edu.my/

2. INTRODUCTION
• People seem to have a natural tendency to sort
out and classify objects of their environment.
• Many uses of soils - agriculture production, to
support buildings and highways, and being
objects of common experience and observation,
soils cannot be excluded from being classified.
• Classification of soils has become more
scientific and organized.
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3. Purpose of Classification
• Classes of the objects under study in a
manner useful for practical and applied
purposes.
• We classify soils to predict their behavior,
identify their best uses, and estimate their
productivity.
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4. The US Comprehensive Soil
Classification System
• Differentiating characteristics selected are
the properties of the soils (including soil
temperature and moisture).
• A formative element from each of the
higher categories, the family, and the
series form the soil name.
• One can make several statements about
soil properties simply from analyzing the
name of the soil.
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5. Structure of the US system
• Six categories from the highest to the
lowest level of generalization.
• The categories include the order,
suborder, great group, subgroup,
family, and series
28-May-15 5

6. COMPREHENSIVE CLASSIFICATION SYSTEM: SOIL
TAXONOMY
• Soil Taxonomy provides a hierarchical grouping
of natural soil bodies.
• The system is based on soil properties that can
be objectively observed or measured rather
than on presumed mechanisms of soil
formation.
– Its unique international nomenclature gives a
definite connotation of the major characteristics
of the soils in question.

7. CATEGORIES AND NOMENCLATURE OF SOIL TAXONOMY
• Nomenclature of Soil Taxonomy
– The names of suborders automatically identify the
order of which they are a part.
– For example, soils of the suborder Aquolls are the
wetter soils (from the Latin aqua, “water”) of the
Mollisols order.
– Likewise, the name of the great group identifies
the suborder and order of which it is a part.
– Argiaquolls are Aquolls with clay or argillic (Latin
argilla, “white clay”) horizons.

8. CATEGORIES AND NOMENCLATURE OF SOIL TAXONOMY
• In the following illustration, note that the three
letters oll identify each of the lower categories
as being in the Mollisols order:

9. SOIL ORDERS
• Each of the world’s soils is assigned to one of
12 orders, largely on the basis of soil
properties that reflect a major course of
development, with considerable emphasis
placed on the presence or absence of major
diagnostic horizons.

10. SOIL ORDERS

11. The classification practice
• One tends to look at the entire soil
population to the extent they are known at
the highest category and place them in
any the twelve soil orders.
• Then, consider the nature and properties
of only the soils within a given order and
determine the suborder.
• The great group of the soil within the
suborder is determined in the same
manner.
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12. ORDER DESCRIPTION
HISTOSOLS Tissue or Organic Soils
ENTISOLS Origin: From recent soils, without pedogenic
developed horizons
INCEPTISOLS Beginning, inception, incipient pedogenic horizons
ANDISOLS High volcanic ash content
ARIDISOLS Dry more than 6 months of the year (not applicable to
Malaysian soil)
MOLLISOLS Soft, organic-rich surface horizons
VERTISOLS Turn self-swallowing clays
ALFISOLS Movement of Al, Fe, and clay into B
SPODOSOLS Wood ash, gray color of E horizon
ULTISOLS Highly leached, clay accumulation in B
OXISOLS Very highly oxidized throughout the profile
Letters in BOLD are the formative elements to denote order in a soil
name 28-May-15 12

13. Simplified key to soil orders
Soil Characteristics Order
1. If the soil has more than 30% organic matter to a depth of 40 cm Histosol
2. Other soils with a Spodic horizon within 2 m Spodosols
3. Other soils with an Oxic horizon within 2 m and no Argillic horizon Oxisols
4.Other soils with more than 30% clay in all horizons – some cracks
when dry at 50 cm
Vertisols
5. Other soils that are dry more than 50% of the year and no Mollic
epipedon
Aridisols
6. Other soils that have an Argillic horizon but a BS at pH 8.2 less than
35% at a depth of 1.8 m
Ultisols
7. Other soils that have a Mollic epipedon Mollisols
8. Other soils that have an Argillic horizon Alfisols
9. Other soils that have an Umbric, Mollic, or Plaggen epipedon, or a
cambic horizon
Inceptisols
10. Other soils Entisols28-May-15 13

14. Figure 3.6 Diagram showing general degree of weathering and soil development in the different soil orders classified in
Soil Taxonomy. Also shown are the general climatic and vegetative conditions under which soils in each order are formed.
SOIL ORDERS

15. SOIL ORDERS
Figure 3.7 Diagram showing the general soil
moisture and soil temperature regimes that
characterize the most extensive soils in each
of eight soil orders. Soils of the other four
orders (Andisols, Entisols, Inceptisols, and
Histosols) may be found under any of the soil
moisture and temperature conditions
(including the area marked EIH). Major areas
of Vertisols are found only where clayey
materials are in abundance and are most
extensive where the soil moisture and
temperature conditions approximate those
shown inside the box with broken lines. Note
that these relationships are only approximate
and that less extensive areas of soils in each
order may be found outside the indicated
ranges. For example, some Ultisols (Ustults)
and Oxisols (Ustox) have soil moisture levels
for at least part of the year that are much
lower than this graph would indicate. (The
terms used at the bottom to describe the soil
temperature regimes are those used in
helping to identify soil families.)

16. SOIL ORDERS

17. Figure 3.8 A simplified key to the 12 soil orders in Soil Taxonomy. In
using the key, always begin at the top. Note how diagnostic horizons
and other profile features are used to distinguish each soil order
from the remaining orders. Entisols, having no such special diagnostic
features, key out last. Also note that the sequence of soil orders in
this key bears no relationship to the degree of profile development
and adjacent soil orders may not be more similar than nonadjacent
ones.

18. ENTISOLS (RECENT: LITTLE IF ANY PROFILE DEVELOPMENT)

19. ENTISOLS (RECENT: LITTLE IF ANY PROFILE DEVELOPMENT)
Figure 3.9 Profile of a Psamment formed on sandy alluvium in Virginia.
Note the accumulation of organic matter in the A horizon but no other
evidence of profile development. The A horizon is 30 cm thick. (Photo
courtesy of R. Weil)

20. INCEPTISOLS (FEW DIAGNOSTIC FEATURES: INCEPTION OF B
HORIZON)

21. Inceptisols

22. ANDISOLS (VOLCANIC ASH SOILS)

23. ANDISOLS (VOLCANIC ASH SOILS)
Figure 3.10 An Andisol developed in
layers of volcanic ash and pumice in
central Africa. (Photo courtesy of R. Weil)

24. GELISOLS (PERMAFROST AND FROST CHURNING)

25. GELISOLS (PERMAFROST AND FROST CHURNING)
Figure 3.11 Gelisols in Alaska. (Left) The soil is in the suborder Histels and has a histic epipedon and
permafrost. This soil was photographed in Alaska in July. Scale in cm. (Right) Melting of the permafrost under
this section of the Alaska Highway caused the soil to lose all bearing strength and collapse. Scale in cm. (Left
photo courtesy of James G. Bockheim, University of Wisconsin; right photo courtesy of John Moore,
USDA/NRCS)

26. HISTOSOLS (ORGANIC SOILS WITHOUT PERMAFROST)

27. HISTOSOLS (ORGANIC SOILS WITHOUT PERMAFROST)
Figure 3.12 A tidal marsh Histosol. The inset shows the fibric (peaty) organic material that contains
recognizable roots and rhizomes of marsh grasses that died perhaps centuries ago, the anaerobic conditions
having preserved the tissues from extensive decay. The soil core (held horizontally for the photograph) gives
some idea of the soil profile, the surface layer being at the right and the deepest layer at the left. The water
level is usually at or possibly above the soil surface. (Photos courtesy of R. Weil)

28. HISTOSOLS (ORGANIC SOILS WITHOUT PERMAFROST)
Figure 3.13 Soil subsidence due to rapid organic matter decomposition after artificial drainage of Histosols in the
Florida Everglades. The house was built at ground level, with the septic tank buried about 1 m below the soil surface.
Over a period of about 60 years, more than 1.2 m of the organic soil has “disappeared.” The loss has been especially
rapid because of Florida’s warm climate, but artificial drainage that lowers the water table and continually dries out
the upper horizons is an unsustainable practice on any Histosol. (Photo courtesy of George H. Snyder, Everglades
Research and Education Center, Belle Glade, FL)

29. ARIDISOLS (DRY SOILS)

30. ARIDISOLS (DRY SOILS)
Figure 3.14 Two features characteristic of some Aridisols. (Left) Wind-rounded pebbles have given rise to a
desert pavement. (Right) A petrocalcic horizon of cemented calcium carbonate. (Photos courtesy of R. Weil)

31. VERTISOLS (DARK, SWELLING, AND CRACKING CLAYS)

32. Vertisol

33. VERTISOLS (DARK, SWELLING, AND CRACKING CLAYS)
Figure 3.15 (a)Wide cracks formed during the dry season in the surface layers of this Vertisol in India.
Surface debris can slough off into these cracks and move to subsoil. When the rains come, water can
move quickly to the lower horizons, but the cracks are soon sealed, making the soils relatively
impervious to the water. (b) Once the cracks have sealed, water may collect in the “microlows,”
making the gilgai relief easily visible as in this Texas vertisol. (Photo (a) courtesy of N. C. Brady; (b)
courtesy of K. N. Potter, USDA/ARS, Temple, Texas)

34. VERTISOLS (DARK, SWELLING, AND CRACKING CLAYS)
Figure 3.16 Vertisols are high in swelling type clay and have wedgelike structures in the subsoil. (a) During the dry
season, large cracks appear as the clay shrinks upon drying. Some of the surface soil granules fall into cracks
under the influence of wind and animals. This action causes a partial mixing, or inversion, of the horizons. (b)
During the wet season, rainwater pours down the cracks, wetting the soil near the bottom of the cracks first, and
then the entire profile. As the clay absorbs water, it swells the cracks shut, entrapping the collected granular soil.
The increased soil volume causes lateral and upward movement of the soil mass. The soil is pushed up between
the cracked areas. As the subsoil mass shears from the strain, smooth surfaces or slickensides form at oblique
angles. (c) An example of a slickenside in a Vertisol. Note the grooved, shiny surface. The white spots in the lower
right of the photo are calcium carbonate concretions that often accumulate in a Bkss horizon. (Diagrams and
photo courtesy of R. Weil)

35. MOLLISOLS (DARK, SOFT SOILS OF GRASSLANDS)

36. MOLLISOLS (DARK, SOFT SOILS OF GRASSLANDS)
Figure 3.17 Correlation between natural
grassland vegetation and certain soil orders is
graphically shown for a transect across north
central United States. The controlling factor, of
course, is climate. Note the deeper organic
matter and deeper zone of calcium
accumulation, sometimes underlain by gypsum,
as one proceeds from the drier areas in the west
toward the more humid region where prairie
soils are found. Alfisols may develop under
grassland vegetation, but more commonly occur
under forests and have lighter-colored surface
horizons.

37. MOLLISOLS (DARK, SOFT SOILS OF GRASSLANDS)
Figure 3.18 Typical landscape dominated by Ustolls (Montana).
These productive soils produce much of the food and feed in the
United States. (Photo courtesy of R. Weil)

38. MOLLISOLS (DARK, SOFT SOILS OF GRASSLANDS)
Figure 3.19 Monoliths of profiles representing three
soil orders. The suborder names are in parentheses.
Genetic (not diagnostic) horizon designations are
also shown. Note the spodic horizons in the Spodosol
characterized by humus (Bh) and iron (Bs)
accumulation. In the Alfisol is found the illuvial clay
horizon (Bt), and the structural B horizon (Bw) is
indicated in the Mollisols. The thick dark surface
horizon (mollic epipedon) characterizes both
Mollisols. Note that the zone of calcium carbonate
accumulation (Bk) is near the surface in the Ustoll,
which has developed in a dry climate. The E/B
horizon in the Alfisol has characteristics of both E
and B horizons.

39. ALFISOLS (ARGILLIC OR NATRIC HORIZON, MODERATELY
LEACHED)

40. Alfisols

41. ULTISOLS (ARGILLIC HORIZON, HIGHLY LEACHED)

42. Ultisols

43. SPODOSOLS (ACID, SANDY, FOREST SOILS, HIGHLY LEACHED)

44. Spadosols

45. SPODOSOLS (ACID, SANDY, FOREST SOILS, HIGHLY LEACHED)
Figure 3.20 (Left) A Spodosol in northern Michigan exhibits discontinuous, wavy Bh and Bs genetic horizons, which comprise the
relatively deep spodic diagnostic horizon. The nearly white, discontinuous eluvial horizon (E) consists mainly of uncoated quartz sand
particles and is an albic diagnostic horizon. The dark, organic-enriched surface horizon (an ochric diagnostic horizon) shows the
smooth lower boundary and uniform thickness characteristic of an Ap horizon formed by plowing after the original coniferous forest
was cleared. (Right) A much shallower Spodosol in Scotland also exhibits a spodic diagnostic horizon comprised of Bh and Bs genetic
horizons. Scale at left marked every 10 cm, knife at right has a 12 cm long handle. (Photos courtesy of R. Weil)

46. OXISOLS (OXIC HORIZON, HIGHLY WEATHERED)

47. Oxisols

48. • Diagnostic horizons are used to differentiate
among soil orders, suborders, great groups, and
subgroups.
i. Surface horizon (A): Epipedon
ii. Subsurface (B): Endopedon
• Combination of specific soil characteristics that are
indicative of certain classes of soils.
• Those which occur at the soil surface are called
epipedons, those below the surface is diagnostic
subsurface horizons (endopedons).
Epipedon & Endopedon

49. Diagnostic Horizons for Classification
• Epipedons
– Albic
– Anthropic
– Histic
– Mollic
– Ochric
– Plaggen
– Umbric
– Arenic
– Grossarenic
• Endopedons
– Agric
– Albic
– Argillic
– Calcic
– Cambic
– Kandic
– Gypsic
– Natric
– Oxic
– Petrocalcic
– Petrogypsic
– Placic
– Salic
– Sombric
– Spodic
– Sulfuric
28-May-15 49

50. Epipedon (A):
• Albic: strongly leached E
horizon
• Anthropic: people-made
mollic horizon
• Histic: Organic soil surface
underlain by mineral soils
• Melanic: Thick, black, friable,
formed in volcanic material
• Mollic: dark, friable, not
strongly acidic
• Ochric: thin or light colored
surface
• Plaggen: people-caused, high
humus .
• Umbric: Acidic, dark
Endopedon (B)
• Agric: tillage-caused, clay and
humus accumulation
• Argillic: clay accumulation
• Cambic: "color" or weakly
developed
• Kandic: argillic with kaolinite-like
clay
• Natric: argillic, high ESP
• Oxic: highly weathered
• Sombric: acidic, humus
accumulation, tropical
• Spodic: acidic, cool area, humus-
sesquioxides accumulation
• Calcic: high CaCO3
• Gypsic: high CaSO4
• Salic: high salt
• Sulfuric: high sulfides

51. SOIL TEMPERATURE REGIME & SOIL
MOISTURE REGIME
• Soil Moisture Regimes (SMR)
– SMR refers to the presence or absence of either
water-saturated conditions (usually groundwater)
or plant-available soil water during specified
periods in the year.

52. COMPREHENSIVE CLASSIFICATION SYSTEM: SOIL
TAXONOMY
• Several moisture regime classes are used to
characterize soils and are helpful not only in
classifying soils but in suggesting the most
sustainable long-term use of soils:
– Aquic
– Udic
– Ustic
– Aridic
– Xeric

53. Classes of the Soil Moisture Regimes
Terms Meaning
Aquic Water saturated for at least enough time (several days) so that
reducing condition exist
Aridic or
Torric
Dry more than half the time when not frozen and never moist more
than 90 consecutive days when soil temperatures are above 8º
C at 50 cm depth
Perudic In most years precipitation exceeds evapotranspiration every
month of the year
Udic In most years, these soils are not dry as long as 90 cumulative days
Ustic In most years, these soils are dry for more than 90 cumulative days
but less than 180 days
Xeric Only in the non-iso temperature areas with dry summers and moist
winters
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54. • Soil Temperature Regimes (STR)
– STR is based on mean annual soil temperature,
mean summer temperatures and the difference
between rainy season and dry season
temperatures, all at a depth of 50 cm from soil
surface.
– Soil temperature regimes, such as frigid, mesic,
and thermic, are used to classify soils at some of
the lower levels in Soil Taxonomy.
– The cryic (Greek kryos, “very cold”) temperature
regime distinguishes some higher-level groups.

55. Classes of the Soil Temperature Regimes
Terms Meaning
Pergelic Mean annual soil temperature < 0º C
Cryic Mean annual soil temperature 0 - 8º C with summer
temperatures less than 15º C
Iso When used as a prefix on the temperature regimes
below, iso refers to soils with the average
temperature for the 3 warmest months differs by
less than 5º C
Frigid and Isofrigid 0º C to < 8º C
Mesic and Isomesic 8º C to < 15º C
Thermic and
Isothermic
15º C to < 22º C
Hyperthermic and
Isohyperthermic
22º C
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56. Malaysian Soil Taxonomy
Category No. of
Taxo
Differentiating characteristics
Order 11 Soil-forming process as indicated by the presence or absence of
major diagnostic horizons
Sub-Order 28 Genetic homogeneity – according to presence or absence of
properties associated with wetness; major parent materials;
nature and origin of organic materials
Great
Group
87 According to profile morphology with emphasis on upper
sequum; degree of weathering; presence or absence of
diagnostic layers, e.g. plinthite
Sub-
Group
279 Central concept for great group
Soil
Family
325 Properties important for plant growth - particle size classes;
mineralogical classes; temperature; and color
Soil
Series
527 Kind and arrangement of horizons, color, texture, structure,
consistence, and major differences in chemical and
mineralogical properties of the horizons.
28-May-15 56

57. Malaysian soil orders VS the US system
Order
Malaysian US System
Organah Histosol
Dankanah Lithosol [shallow soil over hard rock]
Hitanah Spodosol
Abuanah Andisol [volcanic ash]
Oksanah Oxisol
Balanah Vertisol
Kutanah Ultisol
Butanah Mollisol
Jenanah Alfisol
Lahanah Inceptisol
Baranah Entisol28-May-15 57

58. Questions…
Thank You

59. Sample Questions
1. Soil is classified into categories in order to
understand relationship between soils and to
determine the usefulness of soil for particular
soil. Explain how to classify soils based on the
soil taxonomy List the categories or stage in soil
taxonomy classifications based on USDA.
2. List 12 orders of soil and mention it main
characteristic for each order.

60. 3. Name soil orders to which each of the
following soils belong:
Humults
Hapludoxs
Psamments
Orthods
Humits
Fluvents
Argids

61. 6. Name the soil order, soil suborder, soil great
group, soil subgroup, family, and soil
temperature regime for the following soil:
a) Malacca series, Clayey-skeletal,koalinitic,
isohyperthermic Plintic Haplorthox.
b) Pasir Putih series, Fine, Koalinitic, acid,
hyperthermic Aeric Tropaquents.
c) Sungai Buloh series, acidic, isohyperthermic
orthoxic quartzipsmamments.
d) Segamat series, clayey, oxidic,
isohyperthermic Haplic Acrothox