Chapter 6
Modern Soil Classification Systems
Logical and Cognitive Science in Soil
Science
• What are we trying to do?
• How are we going to do it?
• What standards must be established?
Soil Classification
• Organize soil categories for efficient
information
– Storage
– Retrieval
– Communication
• Parent material origins and genetic
information help guide Cognitive Science
Classification
Soil Classification
• How do we classify soils?
– Cognitive Economy – provide maximum information
with least cognitive effort
– Population Structure – what is important to us and
why?
– Expertise effect – recognized experts in area of study
will influence to their benefit
– Culture and Environment -dependant on location,
different features maybe placed on higher level of
importance
– Prototype Concept – collection of samples to
determine what are categories
Indigenous Soil Classification
• Local or Folk Classification
– No formal categorical structure
– Limited geographical scope
– Focused on production soils
• Beneficial for relating knowledge to local
communities
Regional and National Soil
Classification Systems
• Early European System –
– Strongly influenced by Russians
– Used chemical analysis approach
– Low emphasis on Bt Horizon (B horizon with an
accumulation of silicate clays)
– Centuries worth of continuous use
– Kubiena System (1953) – focuses on moisture,
chemical properties, humus type, pedogenic
processes, and micro morphology
Russian Soil Classification
• Started by Dokuchaev and Sibirtsev
• Uses strong genetic (parent material emphasis) and
pedogenic processes
• Hierarchical structure includes
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Trunk
Section
Type
Subtype
Genus
Class
Subclass
Sort
Russian Soil Cont.
• Trunk
– Postlithogenic – soils formed on previous parent
material with negligible modern accumulation on
the surface
– Synlithogenic – soils formed with periodic or
continuous accumulation of new material on the
surface
– Organogenic – soil formation on organic material
Dutch Soils
• Half of the country is below sea level and is
protected by dykes and dams
• Intensively cultivated
• Sandy and Peat type soils
• Classifications
– Order
– Suborder
– Group
– Subgroup
New Zealand Soil
• Structured after US System, but developments
in Andisol and Inceptisol series drove New
Zealand to develop own system.
• Contain only soils in New Zealand
• Contains 15 orders focusing in on volcanic
activity focusing on Allophanic and Pumice
soils
Canadian Soil
• A system that is used only to classify soils
present in Canada
• Hierarchy includes
– Order
– Great Group
– Subgroup
– Family
– Series
• 10 orders and 31 great groups
Canadian Soil
• Order – soil properties reflecting the effects of the
dominant soil-forming processes and the soil
environment
• Great Group – properties reflecting the strength of
dominant pedogenic processes in addition to the major
one
• Sub-group – taxa based on congruence with the central
concept of a group and the associated kind
arrangement of horizons
• Family – taxa seperated on the basis of minerology,
texture, and climatic factors within each family
Aussie Soil
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Wide range of soil
Wide range of climates
Wide range of precipitation
Hierarchy
– Horizon Pedounit – a combination of similar horizons
– Group – a collection of pedounits that are similar to
soil mapping characteristics equivalent to US soil
series
– Subclass – groups placed together because of
similarities in two or three kinds of horizons
– Class – highest level of generalization
Brazilian Soil
• 13 Classes
• Based of the 1938 US soil series
• Emphasis placed on chemical aspects because
relative low fertility and focus on soil
amending
Chinese Soil
• 33 horizons
• 25 diagnostic properties
– Soil temperature
– Soil moisture regime
• Focus on soils which have been cultivated for
thousands of years in flood irrigation of rice
paddy
• Incorporates indigenous names and current to
improve understanding
World Reference Base
• An effort to standardize world wide soil taxa
• 32 groups
• Next tier has group of prefixes and suffixes to
modify terms
Numerical Classification of Soils
• Ideal natural taxonomy is one in which taxa have
greatest information
• Every natural feature is of equal wieght in construction
• Affinity is a function of proportion of features in
common
• Affinity is independent of phylogeny (evolution)
• Negatives
– Potential loss of information
– Selection, measurement, and coding are subjective
– Complex
Indigenous Soil Classification