Classification of Soils Modern Soil Classification Systems

1
Classification of SoilsModern Soil
Classification Systems

• Lecture 9
• Soil Science 325
• Reading
• SGC Chapter 6

2
Why Organize Information?

• To make it understandable and useful
• To create recognition systems for significant
  attributes and properties
• To create logical decision networks that enhance
  technology transfer
• To establish a hierarchy in which new knowledge
  can be incorporated

3
General Principles of Natural Classification
Systems

• Groupings of general or universal natural
  relationships that are understandable or
  predictable from available information.
• Similar characteristics or attributes are grouped
  together on the basis of their properties.
• A ranking (hierarchy) of attributes according to
  how important they are to the existence of the
  item being classified.
• It is technically impossible to use all
  properties of the items being classified.

4
Why Classify Soils?

• Organize knowledge to enable investigation and
  communication (structure/organization)
• Provide framework for establishing relationships
  among soils and their environment (scientific)
• Establish groupings for interpretations
  (utilitarian)
• Optimal use
• Hazard/limitation/remediation assessment
• Potential productivity
• Framework for technology transfer/information
  dissemination

5
Kinds of Soil Classification Systems

• Genetic
• Based on presumed soil-forming processes
• Natural
• Based on observed properties
• Technical
• Based on a particular intended use (e.g.,
  engineering) or inferred properties

6
Early Chinese soil classification system(Yao
patriarchy, 2357-2261 BC)

• Soils graded into nine classes based on their
  productivity, including yellow, soft soils
  (loess?) and red, rich clayey soils (limestone
  derived?) in the top and second category,
  respectively
• Property taxes were based on the size of the
  holding and soil productivity

7
Indigenous soil classification systemthe Sahel
region of Mali
Dugukóló (soil)
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Soil classification systemSahel region of Mali
Dugukóló (soil)
Bógó (clay)
Céncén 100 (sand)
Bélé (rock)
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Soil classification systemSahel region of Mali
Dugukóló (soil)
Bógó (clay)
Céncén 100 (sand)
Bélé (rock)
Blen (red)
Guema (white)
Fin (black)
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Soil classification systemSahel region of Mali
Dugukóló (soil)
Bógó (clay)
Céncén 100 (sand)
Bélé (rock)
Blen (red)
Guema (white)
Fin (black)
Manama (fine clay)
Kirikiri (very fine clay)
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Soil classification systemSahel region of Mali
Dugukóló (soil)
Bógó (clay)
Céncén 100 (sand)
Bélé (rock)
Blen (red)
Guema (white)
Blen (red)
Guema (white)
Fin (black)
Manama (fine clay)
Kirikiri (very fine clay)
Fin (black)
(Malian Institut dEconomie Rurale (IER) in Mopti
and Sotuba, Mali)
12
Early European soil classification system
(Fallou, 1862)
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Global Soil Classification Systems

• Soil Taxonomy
• Legend of the Soil Map of the World (FAO-UNESCO,
  1974)
• World Reference Base (WRB) for Soil Resources
  (ISSS-ISRIC-FAO 1994, 1998)

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Regional/continental Soil Classification Systems

• French systems central and west Africa, former
  USSR
• China
• Australia
• Ecological region systems Brazil, New Zealand,
  Canada, Great Britain and Wales, South Africa

15
Categories in U.S. Soil Taxonomy

• Order key soil properties resulting from major
  soil-forming processes (epipedons, subsurface
  horizons, materials, characteristics) - 12
• Suborder key soil properties that are major
  controls on soil-forming processes, e.g., soil
  climate (most orders) kinds of salts
  (Aridisols) kinds of soil parent materials
  (Entisols) degree of decomposition (Histosols)
  presence or absence of cryoturbation (Gelisols) -
  64
• Great Group key soil properties that are
  additional controls on soil genesis (diagnostic
  horizons) - 325
• Subgroup central concept (Typic), intergrades,
  extragrades ca. 2 400
• Family properties important to plant growth
  (texture, mineralogy, soil temperature regime,
  etc.) ca. 7 500
• Series soil morphology ca. 19 000

16
FAO-UNESCOFood and Agriculture Organization -
United Nations Education, Scientific, and
Cultural OrganizationISSSInternational Society
of Soil Science

• Soil mapping effort began in 1960
• Compilation of world soil map (15,000,000) and
  approximations 1968-1974, with first publication
  of the world map in 1974.
• Major revision in 1988
• Presently there are 28 soil groupings and153 soil
  units based on diagnostic horizons and properties

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FAO-UNESCO/ISSSObjectives

• First appraisal of worlds soil resources
• Technology transfer among countries
• Global soil taxonomy
• Framework for developing areas
• Basic document for teaching and research
• Strengthen international cooperation

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FAO Soil Map of the World, 1992
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Legend for the FAO Soils Map
http//www.fao.org/waicent/faoinfo/agricult/agl/ag
ll/key2soil.stm
20
Equivalent soil types FAO Soil map and Soil
Taxonomy
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Recognized horizons in the revised FAO Legend for
the Soil Map of the World (1988)

• Albic E
• Argic B
• Equivalent to argillic
• Calcic
• Cambic B
• Ferralic B
• Low CEC
• Fimic A
• Long term cultivation

• Gypsic
• Histic H
• Mollic A
• Natric B
• Ochric A
• Petrocalcic
• Petrogypsic
• Spodic B
• Sulfuric
• Umbric

22
Recognized properties in the revised FAO Legend
for the Soil Map of the World (1988)

• Abrupt textural change
• Andic
• Calcareous
• Calcaric
• Calcareous soil material
• Continuous hard rock
• Feralic
• Ferric
• Coarse mottles or nodules
• Fluvic
• Water-deposited sediments on surface
• Geric
• Low to negative CEC
• Gleyic
• Gypsiferous
• Interfingering
• Nitic
• Strong structure

• Organic materials
• Permafrost
• Plinthite
• Salic
• Slickensides
• Smeary consistence
• Sodic
• ESP gt 15 or exchangeable Na Mg gt 50
• Soft powdery lime
• Comminuted calcium carbonate
• Stagnic
• Reducing condition from ponded water
• Strongly humic
• Sulfidic material
• Tonguing
• Vertic
• Weatherable minerals

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World Reference Base for Soil ResourcesObjectives

• Provide an international framework using FAO
  revised legend
• Assist in technology transfer/ applications in
  agriculture, geology, ecology, etc.
• Incorporate soil topo- and chronosequences
• Pursue and develop a strongly morphological
  rather than purely analytical approach to soil
  classification

24
World Reference Base for Soil ResourcesConcepts

• Utilize diagnostic horizons, properties, and soil
  materials for classification
• Emphasizes soil-forming processes
• No climatic parameters
• Two levels (soil groups and units)
• 30 reference soil groups represent major soil
  regions
• Supplements rather than replaces national systems
• Historical nomenclature

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What is a reference soil?
Interpretation
Solum
Conceptual Solum
Choice
Study
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The reference soil groups of the World Reference
Base, (ISSS-ISRIC-FAO, 1998)

• Histosols
• Kastanozems
• Leptosols
• Lixisols
• Luvisols
• Nitisols
• Phaeozems
• Planosols
• Plinthosols
• Podzols
• Regosols
• Solochaks
• Solonetz
• Umbrisols
• Vertisols

• Acrisols
• Albeluvisols
• Alisols
• Anthrosols
• Andosols
• Arenosols
• Calcisols
• Cambisols
• Chernozems
• Cryosols
• Durisols
• Ferralsols
• Fluvosols
• Gleysols
• Gypsisols

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Diagnostic horizons for the WRB(ISSS-ISRIC-FAO,
1998)

• Natric
• Nitic
• Ochric
• Petrocalcic
• Petroduric
• Petrogypsic
• Petroplinthic
• Plinthic
• Salic
• Spodic
• Takyric
• Crusted surface
• Umbric
• Vertic
• Vitric
• Yermic
• Loamy vesicular dry crust

• Albic
• Andic
• Anthropedogenic
• Argic
• Calcic
• Cambic
• Chernic
• Well-structured mollic
• Cryic
• Duric
• Ferralic
• Ferric
• Folic
• Fragic
• Fulvic
• Gypsic
• Histic
• Melanic
• Mollic

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Properties and soil materials recognized in the
WRB
Soil materials
Soil properties

• Anthropogeomorphic
• Calcaric
• Fluvic
• Gypsiric
• Organic
• Sulfidic
• Tephric

• Abrupt textural change
• Albeluvic tonguing
• Penetrations of clay and Fe-depleted material
  into argillic
• Alic
• Aridic
• Continuous hard rock
• Feralic
• Geric
• Gleyic
• Permafrost
• Soft powder lime
• Stagnic
• Strongly humic

Web address for WRB Taxonomy World Reference
Base Handbook
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Some Soil Classification Systems for Individual
Countries

• Pedological Reference Base (France)
• Former USSR
• China
• Australia
• Brazil
• Canada
• England and Wales
• New Zealand
• South Africa

30
Pedological Reference Base (PRB) French Soil
Classification SystemConcepts

• A global system
• Reference rather than hierarchical system
• Emphasizes composition of soil mantle, soil
  structure, and soil evolution
• Two categories groupings and references
• 40 major groupings and 90 references

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Major Reference Groupings in the PRB

• Alocrisols
• Alu-Andosols
• Andosols
• Anthroposols
• Arenosols
• Brunisols
• Calcarisols
• Calcisols
• Calcosols
• Dolomitosols
• Ferralosols
• Fersialsols
• Fluvisols and Thalassosols
• Gypsosols
• Histosols
• Lithosols
• Luvisols
• Magnesisols

• Organosol
• Pelosols
• Peyrosols
• Planosols
• Podzosols
• Rankosols
• Reductisols Redoxisols
• Regosols
• Rendisols
• Rendosols
• Salisols
• Sodisols
• Sulfatosols
• Thiosols
• Veracrisols
• Vertisols
• Vitrandisols
• Yermosols

32
Former USSR Soil Classification System

• Published 1977 (English version 1986)
• Multiple land use
• No hierarchical structure
• Strong emphasis on knowledge of soil-forming
  processes (i.e., genetic)
• Four categories types, subtypes, genera, species
• 71 (!) soil types 194 subtypes
• Historical Russian terminology

33
Examples of types and subtypes in the 1986 USSR
soil classification system (VASKhNIL)

• Bleached meadow soils
• Podzolized bleached meadow soils
• Podzolized gley bleached meadow soils
• Meadow Chernozem-like soils
• Chernozem-like dark meadow soils
• Dark meadow prairie soils
• Dark moist-meadow prairie soils

• Chernozems
• Podzolized chernozems
• Leached chernozems
• Typical chernozems
• Ordinary chernozems
• Southern chernozems
• Mountain chernozems
• Meadow Chernozems
• Meadowy chernozemic soils
• Meadow chernozems soils

34
Chinese Soil Taxonomic System

• Structured after Soil Taxonomy
• Global system
• Seven categories order, suborder, group,
  subgroup, genus, species, and variety
• Order based on major soil-forming processes
• suborder based on soil properties reflecting
  dominant soil processes
• group reflects secondary processes
• subgroup represents deviation from central
  concept of group
• 13 orders 33 suborders 78 groups 301 subgroups
• Nomenclature a mixture of old and new names
• Uses diagnostic horizons and characteristics

35
Recognized Orders in the Chinese Soil Taxonomic
System (1994)

• Andisols
• Anthrosols
• Aquisols
• Aridisols
• Ferrallisols
• Fersiallisols
• Halosols

• Histosols
• Isohumisols
• Primarosols
• Siallisols
• Spodosols
• Vertisols

36
Australian Soil Classification System

• Genetic system
• For use in Australia only
• Unusual terminology
• 14 orders
• Similar taxonomic levels as Soil Taxonomy

Website for more information Keys to Australian
Soil Taxonomy
37
Soil orders in the Australian Soil Classification
System (1996)

• Anthroposols
• Calcarosols
• Chromosols
• Dermosols
• Ferrolsols
• Hydrosols
• Kandosols

• Kurosols
• Organosols
• Podosols
• Rudosols
• Sodosols
• Tenosols
• Vertosols

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Canadian Soil Classification System

• Published 1978 rev. 1987
• Natural system
• Applicable to all of Canada
• Hierarchical 5 categories (order, great group,
  subgroup, family, series)
• 10 orders, 31 great groups

39
Soil Orders in the Canadian Soil Classification
System (1987)

• Brunsolic weak to moderately developed soils
• Chernozemic soils with dark-colored, high
  base-saturated A gt10 cm thick, between 1-17 OC
• Cryosolic soils with permafrost within 2 m of
  surface
• Gleysolic soils permanently or temporarily
  saturated with water and which experience
  reducing conditions
• Luvisolic soils with a subsurface horizon
  showing evidence of clay accumulation
• Organic Soils dominated by organic horizons
  showing evidence of clay accumulation
• Podzolic soils having podzolic B horizon
• Regosolic little or no pedogenesis
• Solonetzic soils having a subsurface horizon
  with a prismatic or columnar structure and a
  Ca/Na ratio gt 10
• Vertisolic soils with high shrink-swell clay
  contents

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Approximate comparisons of Soil Taxonomy, World
Reference Base, and the Canadian Systems
41
Conclusions Soil Classification Systems

• Necessary to organize soil information
• Indigenous systems show the basic level of
  information organization
• Some classification systems are more intuitive
  than others
• There is not a clear global system for soil
  classification, but most systems are
  translatable