Agriculture Reference
In-Depth Information
The Ýrst version of WRB (Working Group RB, 1998a, b, c) was presented in 1998 at the 16
th
ISSS Congress in Montpelier and was endorsed, in a historical motion, as the ofÝcial soil correlation
system of the International Union of Soil Sciences. The detailed characteristics of the system
(Nachtergaele et al., 2000; Deckers et al., 2001) are described by others and will not be treated
here, but major changes with the Ýrst draft (and implicitly the FAO Revised Legend) include the
following:
¤
The development of a two-tier system in which the Ýrst level describes and deÝnes, in simple
terms, 30 Soil Reference Groups and classiÝes them with a key. The second level is composed of
a list of uniquely deÝned qualiÝers (121 of them) that can be attached to the Soil Reference Groups.
For international soil correlation purposes, a speciÝc preferred priority ranking is given for each
Soil Reference Group. This approach results in a very compact system.
¤
The deÝnition of a number of preÝxes that permit the precise description for where a soil phe-
nomena occurs (epi, endo, bathy, etc.) or how strongly it is expressed (hypo, hyper, petri). This
results in the ability to give a very precise characterization of the soil.
¤
The explicit emphasis put on morphological characterization of soils rather than analytical proce-
dures. This aim is not always fully realized, but it is at least an attempt to permit soil classiÝcation
to take place in the Ýeld, rather than in the laboratory.
¤
The parallel publication of a WRB topsoil characterization system (Purnell et al., 1994; URL:
ftp://ftp.fao.org/agl/agll/docs/topsoil.pdf
), with about 70 different topsoil combinations recognized,
that permits classiÝcation in a much more elaborated way than possible with six epipedons, the
most important portion of the soil for most of its uses.
The WRB system as such has met with considerable success since its ofÝcial endorsement by
the IUSS in 1998. In the 3 years since its appearance, 3000 WRB topics have been sold or distributed,
a web site was established (
) , the system has
been translated into 10 languages, it has been adopted in several regions (European Union, West
Africa, Global SOTER) and countries (Italy, Lithuania) for national correlations or classiÝcation
purposes, and has led to a revival of the interest in soil classiÝcation and soil nomenclature.
The developments described above and the association of FAO with the WRB effort indicate
that the latter has effectively replaced the FAO legend with a FAO-backed and internationally
endorsed World Soil Reference system.
http://www.fao.org/ag/AGL/agll/wrb/wrbhome.htm
FUTURE DEVELOPMENTS
The World Reference Base for Soil Resources will be re-edited as a one-volume student version
that includes some minor changes and additions (Driessen et al., 2001), including rules for arriving
at the preferred ranking of qualiÝers. The topic will be followed by a CD-ROM containing more
than 1500 pictures of landscapes and soil proÝles classiÝed using WRB.
Future developments of WRB could include the following:
¤A much more explicit emphasis on soil characteristics as the base for soil classiÝcation and
correlation, rather than continuing to provide lip service to pedogenesis as the underlying central
factor for combining soils in classes or for subdividing them.
¤
An explicit recognition that the subdivisions of the Soil Reference Groups are largely arbitrary
and that the hierarchical ranking of these subdivisions makes little scientiÝc sense. This can be
achieved by using all relevant qualiÝers as a single ÑÞatÒ second level. The order in which the
qualiÝers are used would be left open and be a function of the purpose of the soil survey. For
international soil correlation purposes, a reasoned preferred ranking order is proposed (Nachter-
gaele et al., 2001). The application would result in greater transparency, permit further simpliÝ-
cations, and, more importantly, would allow a full transfer of soil proÝle information, which is
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