Agriculture Reference
In-Depth Information
For example, diagnostic horizons with high content of speciÝed kinds of artifacts and an anthroturbic
horizon of highly mixed soil materials that contain remnants of diagnostic horizons could be deÝned.
However, if limited to morphological evidence in the pedon, this approach would fail to capture
many of the anthropogenic soils, because of their lack of morphological evidence of anthropogen-
esis. As a result, soils of similar process of origin would occur both in classes of anthropogenic
soils and soils formed under natural conditions.
The second approach to incorporating anthropogenic processes is to allow previously unused
observations, such as landform type (anthropogenic vs. natural), relational observations and data
(to include historical records), and the knowledge of process of formation, to be used to identify
the anthropogenic soil order at the beginning of the key to soil orders. These new types of evidence
could be used to distinguish different types of anthropogenic soils, but would be restricted from
use in other parts of the keys. As precedent for restricting the use of these criteria from other parts
of the key, separate control sections, epipedons, diagnostic horizons, and diagnostic materials
already exist for organic soils in Soil Taxonomy (Soil Survey Staff, 1999), and most of them cannot
be used in mineral soil orders. Additionally, the family level is full of examples where classes and
categories are applied only to a restricted set of mineral soils. Alternative particle-size classes,
mineralogy classes, and reaction classes are used and deÝned based on the higher classiÝcation of
the soil in question.
Anthropogenic soils occur on anthropogenic landforms, such as rice paddiess, old raised Ýelds,
landÝlls, mine spoils, excavation areas, Ýll areas, disturbed construction sites, and others. Experi-
enced soil classiÝers are also experienced in landform identiÝcation, which is an integral component
of soil survey. The identiÝcation of an anthropogenic landform could be used as criteria or partial
criteria for identifying an anthropogenic soil and placing it in a class apart from soils that formed
in natural, undisturbed landscapes. This approach would work well for those soils that have
experienced signiÝcant physical alteration, but it does not address anthropogenic processes that
result only in chemical alteration. Decisions will have to be made regarding the kind and degree
of anthropogenic alteration to be recognized in Soil Taxonomy at various levels.
Relational observations in combination with data could be used to address issues such as
anthropogenic alteration of soil chemical properties. The use of relational data is not unprecedented
in Soil Taxonomy, although it may only be used with respect to the identiÝcation of anthropogenic
processes as originally included in the system. Anthropic epipedons found in soils of kitchen
middens are described as having high base saturation, compared to adjacent soils. Data alone do
not address the source of an observed property, but if used in conjunction with relational data, such
as comparisons between limed soils and soils that have not been limed, criteria could be developed
for identifying the effects of these kinds of anthropogenic processes. Similarly, eroded Mollisols
could be identiÝed in comparison to uneroded counterparts to assess the degree of accelerated
erosion. However, a proposal to use relational data for this purpose was recently considered and
rejected by the Soil Taxonomy Committee. The review expressed the concern that consistency
among soil scientists in interpreting the deÝnition of taxa would be threatened if the classiÝcation
of soils based on properties that may have been present were to be allowed. This decision may
restrict the use of relational data as criteria for classes of naturally formed soils, but it may not be
viewed negatively if restricted for use within classes of anthropogenic soils.
Although strictly avoided for classifying soils formed under natural soil-forming conditions,
the use of knowledge of process of formation could be allowed for use in classifying anthropogenic
soils. Classifying soils developed in mine spoil as Spolanths could be simply based on knowledge
that the soil in question is formed in material that originated as a result of the mining process
(Sencindiver and Ammons, 2000). Diagnostic horizons may not be required to identify a soil to
the order or suborder level, but they may be very helpful in deÝning classes in the lower categories.
Meaningful separations within suborders (Spolanths, for example) should be based more on observ-
able morphological characteristics or chemical properties that affect the use and management of
these soils, or that imply the direction of genesis of these soils in response to the active factors of
