Agriculture Reference
In-Depth Information
French researchers have been particularly active in this Ýeld for some years. Erhart (1956) and
later on Kilian (1974) introduced the importance of geomorphology in soil genesis, and that the
assessment of morphogenesis/pedogenesis is at the basis of the functioning of soils on slopes.
A team from the ScientiÝc Research OfÝce for Overseas Territories (ORSTOM), led by Boulet
(Boulet et al., 1982), revealed, essentially in tropical environments, the importance of differentiating
between lateral transfers within a toposequence and those of the Ñtransformation systemsÒ at the
level of the interfaces between horizons (Boulet et al., 1984; Fritsch et al., 1986). These studies
were carried out through an approach titled Ñstructural analysis,Ò based mainly on the observation
of morphological parameters. At this time, Boulaine (1986) described several ÑpedosystemsÒ
stemming from the lateral dispersion of certain constituents. Therefore a methodology was proposed
that considers the need for knowledge of soil arrangements within the landscape as a prerequisite
for mapping as a whole (Brabant, 1989). Different syntheses on the approaches to the understanding
of spatial soil arrangements and their mapping, in temperate as well as in Mediterranean and tropical
environments, were carried out (Ruellan et al., 1989; Jamagne and King, 1991; Jamagne et al.,
1993; Ruellan and Dosso, 1993; King et al., 1994a). The concepts of a Ñspatial organization modelÒ
of soils and Ñsoil functioning unitsÒ were consequently introduced by King et al. (1994b).
DEVELOPMENT IN TYPOLOGIES AND SOIL MAPPING
During the last decades, there have been tremendous advances in information technology and
manipulation of spatial data. Quality control in data acquisition has been achieved by development
of manuals such as the Soil Survey Manual (Soil Survey Staff, 1961; USDA-SCS, 1993), and
through the recognition of the importance of the relationships between soil mapping and classiÝ-
cation (Simonson, 1989). Concerning the processing of collected data, statistical methods and
especially geo-statistics have been used more and more frequently for the drawing up of ÑSpatial
Information SystemsÒ (Webster, 1977; Webster and Oliver, 1990). Computer technology has become
a very powerful tool that is essential for the processing of georeferenced data, especially with the
introduction of the Geographic Information Systems (GIS) (Burrough, 1986). The combination of
all existing statistical and computing techniques led to very powerful methods, notably those for
assessing the uncertainties linked to the interpretations. Nevertheless, a judicious use of these tools
is necessary (McBratney, 1992).
Mermut and Eswaran (2001) have recently synthesized the major developments in soil science
that have occurred since the 1960s, highlighting the application of these new techniques in soil
science: computers, statistics, remote sensing, GIS, etc. The use of DEMs (Digital Elevation
Models) in the thematic domain in soil science dates from a little over 10 years ago. The variation
intervals are inconsistent, going from grids of a few meters up to 1000 m. Recent contributions to
the use of DEMs for modelling ÑLandscapesÒ and ÑSoil-LandscapesÒ include those of Skidmore
et al. (1991), Bell et al. (1994), Odeh et al. (1994), Thompson et al. (1997), Sinowski and Auerswald
(1999), King et al. (1999), Chaplot et al. (2000), and Thompson et al. (2001). These modern
techniques, enabling a more dynamic approach to spatial analysis, have resulted in the progressive
abandonment of traditional mapping procedures in favor of an approach that gives priority to soil
arrangements in the landscape, as elaborated by Jamagne (1993), King et al. (1994), Jamagne et al.
(1995), FAO-ISRIC (1995), and EC (1998).
Cartography and Classification
An important development has taken place, over the years and by the experience acquired, in
the conceptions of the deÝnition and of the contents of the mapping units. This started from the
notion of Ñsoil seriesÒ introduced by the American school of thought (Soil Survey Staff, 1961;
