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(mine spoils),
technic
(mineral wastes),
urbic
(urban wastes). Urbi should
not be confused with orbi. It is of course the desire to move pedology
closer to the users. But the latter have need of a simple vocabulary.
On the other hand, there is realization that a terminology of fewer
than 300 words is enough for describing all the soils of the world,
including those modified by man. Also, the WRB has reached great
maturity in regard to the list of References and that of diagnostic
Horizons. It is easy to use. An atlas with photographs is available
(Bridges
et al.
1998). The system also improves the classification of
tropical soils, which, excepting orthotypes, are often difficult to classify
(Chap. 5). The WRB is now the standard system at the international level.
It has the support of the FAO, the IUSS and the ISRIC (
International Soil
Reference and Information Centre
, Wageningen). Thus, it cannot be ignored
and, moreover, it is available on the Internet. It is practically obligatory to
refer to it for identifying the soils mentioned in scientific publications.
4.3 THE AMERICAN CLASSIFICATION
4.3.1 Origin and Objectives
As in the other countries, the Americans started by using empirical
classifications based on the physical properties of the soils. Such
was the attempt by Whitney (1909). Then, under the influence of the
Dokuchaev school, they moved to genetic classifications: that of Coffey
(1912) and then that of Marbut (1927) that introduced the idea of
Pedocals
(accumulation of calcium carbonate) and
Pedalfers
(accumulation of
iron and aluminium). Last came the classification of Kellogg (Baldwin
et al
. 1938). This classification also distinguished zonal, intrazonal and
azonal soils. One can understand it better by consulting the reviews on
the topic (Helms
et al.
2002; Paton and Humphreys 2007).
Starting from the notion that pedogenetic processes are poorly
understood and difficult to differentiate, it was desired to go back to a
more objective classification based on directly observable or measurable
properties. Thus was born in Washington, after several attempts, the
7th Approximation (USDA 1960) under the guidance of Guy D. Smith,
Director of
Soil Survey Investigations
in the
Soil Conservation Service
,
USDA. Smith did not neglect pedogenesis for all that. He wrote '
Genesis
does not appear in the definition of the taxa but lies behind them
' (Bockheim
and Gennadiyev 1995). The Americans R.W. Arnold and H. Eswaran
were to add later, in 1989, at a working meeting that took place in France:
the observed features are related to conceptual models of soil genesis
. Since 1975,
the American system has improved, changed its name and became
Soil
