Agriculture Reference
In-Depth Information
how individuals are allocated to them. This, or a modiÝed approach, will enable a better rational-
ization for the number and selection of categories in a classiÝcation system.
Although aggregation of Ýeld-level units to higher and more abstract groups is probably the
most appropriate procedure in natural systems, some soil classiÝcation systems have begun by
deÝning the highest category, usually based on traditional systems or preconceived notions. Many
of the early systems, including WRB, have adopted this procedure. Lack of detailed information
on the soil individual is usually the reason. The Russian system (Shishov and Sokolov, 1990) adopts
both procedures. Having deÝned the Types, higher units (Order and Trunk) of the Russian system
are formed by aggregation of the Type, whereas lower units are formed by desegregation of the
Types. In Soil Taxonomy, the soil series is the lowest category, and these are aggregated in Ýve
higher levels. Conceptually, the soil individual is the polypedon, which is constituted by the pedon
and acceptable variability.
Principles
The principles of Soil Taxonomy set forth by Cline (1949) and others provide the basis for the
architecture of the classiÝcation system that has been developed. They have served to guide the
modiÝcation of the system since its publication in 1975. Many listed below are re-enforcement of
the principles existing in the Ýrst edition (Soil Survey Staff, 1975). A few reÞect the changes that
have evolved with the systematic application of the system in the United States and globally. The
fundamental principles were guided by the system of logic enunciated by John Stuart Mill (Cline,
1963) and do not change.
Soil Taxonomy is designed for the making and interpreting of soil surveys, which is the
most important use of Soil Taxonomy. It was and is designed as a tool for correlation in soil
survey programs. It was also designed as the technical language of communication between
soil scientists and those knowledgeable about soils. The categories of the system (Ahrens and
Arnold, 1999) enable one to make interpretations regarding use and performance of soils; the
accuracy of such interpretations is a function of the categoric level, with speciÝcity increasing
at lower categories. For site-speciÝc predictions and management, information contained in
the lowest category must be supplemented with information about those properties that show
spatial (short distance) and temporal variability. Basic considerations for the principles include
notions of the following:
1.
Equity. Each category in the system should provide a place for all soils in a landscape, or have
the capability to provide such a place without distortion of the system.
2.
Transparency. The categories of the system must have unambiguous deÝnitions and clearly stated
functions; knowledgeable persons equipped with the same information must arrive at the same
classiÝcation.
3.
Science-based. The system should not prejudice future applications. This is ensured by adhering
to logical scientiÝc rules and by minimizing the use of biases, popular feelings, and traditional
approaches; historical information must be continually validated for its relevance and acceptance.
4.
Architecture and linkage. The design of a classiÝcation system should facilitate its use in digital
processing systems, and where possible, with easy linkage to other natural resource classiÝcation
systems.
5.
Ecosystem links. As soils are a component of an ecosystem, ecosystem parameters are valid as
surrogates for deÝning categories, particularly at the high categories.
6.
Flexibility. To serve its intended purpose and to reduce subjectivity in application of the system,
Þexibility should not result in distortion of system integrity.
