Agriculture Reference
In-Depth Information
or FAO. There have been periods of aggressive debate over the role and application of general-
purpose national schemes.
A persistent problem has been the limited appreciation of how the utility of a general-purpose
soil classiÝcation is constrained by contrasting patterns of covariance in soil populations at local,
regional, and national levels. For practical reasons, most Australian classiÝcation systems have
depended heavily on morphological criteria. However, covariance between soil morphological
properties and more relevant chemical, physical, and mineralogical properties is complex and
sometimes poor (e.g., MacArthur et al., 1966; Webster and Butler, 1976; Butler and Hubble, 1977;
McKenzie and MacLeod, 1989; Fitzpatrick, 1996; Fitzpatrick et al., 1999).
The substantial literature on spatial variability (e.g., Beckett and Webster, 1971; Wilding and
Drees, 1983; Burrough, 1993) demonstrates that soil properties have varying levels of covariance.
As a consequence, we should have modest expectations of the capacity of general-purpose classi-
Ýcation systems to discriminate effectively against a broad range of criteria (e.g., soil fertility,
hydraulic properties, engineering, genesis) across a wide range of soil conditions.
Several critics contend that general-purpose systems have inherent, and sometimes severe,
limitations (e.g., Gibbons, 1961; Webster, 1968, 1977; FitzPatrick, 1971; Butler, 1980). A typical
opinion is shown in the following statement by White (1996): ÑThe effort put in to developing
general-purpose soil classiÝcation systems in Australia seems to have been largely unrewarded in
terms of the use made of this information by land managers.Ò Basher (1997) in a paper titled ÑIs
pedology dead and buried?Ò and others (e.g., Dudal, 1987; Zinck, 1993; White, 1993; Yaalon, 1996)
suggest that the decline in the use of general-purpose soil classiÝcation systems can be ascribed
to a range of factors, including the following:
¤
The specialized terminology used to name and classify soils in soil map legends and reports, and
the range of systems in use for classifying soils
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The need for adjustments in soil survey techniques and soil classiÝcation to meet the requirements
of potential users
¤
InsufÝcient attention given to presenting information in an accessible, purpose-orientated, user-
friendly language and format
¤
Inadequate use of soil class criteria that are important to land use (i.e., physical properties such
as porosity, inÝltration rate, and permeability properties of the surface layer of soil) and an over-
emphasis on taxonomic class criteria
In this chapter, our Ýrst objective will be to show that general-purpose classiÝcations are
being modiÝed to remedy the limitations. The enduring value of good general-purpose classiÝ-
cation systems will be as a tool to communicate soil information nationally. Australians have
recognized this more clearly in recent times. Agencies undertaking soil and land resource surveys
now provide predictions and interpretations of how a range of land qualities (e.g., salinity) vary
across the landscape, rather than provide a single map of soil types. Various special-purpose
classiÝcation systems have been developed for utilitarian ends, and some examples are considered
in later sections. Descriptions of soils using national taxonomic schemes are used to aid com-
munication, and this is increasingly being supported by good visual material to highlight differ-
ences between soils.
Some critics have also dismissed general-purpose soil classiÝcation systems as having limited
value for soil fertility work (e.g., White, 1996). There are few who would expect general-purpose
systems to provide good predictions of nutrient availability because of the covariance issues already
mentioned and the strong dependence of these attributes on management history. Furthermore, most
classiÝcation systems use less dynamic variables as differentiae to ensure stable allocations of
proÝles to classes over time. However, classiÝcation systems do have considerable value for
stratifying behavior of soil groups in terms of nutrient dynamics. Such recognition (e.g., Fitzpatrick
et al., 1999; NLWRA, 2001) has led to more constructive dialogue between the soil testing and
pedological communities in Australia.
