Agriculture Reference
In-Depth Information
INTRODUCTION
Soil classiÝcation has played a central role in soil science over the last century. As soil surveys
were made, the understanding of relationships between soils and the soil-forming factors has increased,
and this is reÞected in the classiÝcation systems. Distinction among different types of soil helped to
categorize and stratify the large body of information being assembled during soil survey, and this was
certainly important in the pre-computer periodÐbut it remains important now. The earlier notion that
the instant availability of basic data retrieved using information systems would make soil classiÝcation
less relevant has proven to be unrealistic. Huge volumes of unstratiÝed data tend to confuse, rather
than enlighten, the prospective user. As time went by, soil classiÝcation systems developed using
different categories, ranging from orders to soil series. Their practical application under Ýeld condi-
tions was facilitated by emphasis on soil morphological features, allowing classiÝcations to be made
in the Ýeld without having to take and analyze many samples. The problem, of course, has always
been the fact that soils are not separate individuals, as are animals and plants. Soils form continuous
bodies in landscapes, thus soil taxonomic systems have a different character from that of other
taxonomic systems. But several taxonomic systems have been completed, and are now in use, such
as Soil Taxonomy (Soil Survey Staff, 1998) and the FAO ClassiÝcation system (FAO, 1998). The
time is right to ask whether these systems have now found their Ýnal form, or whether new develop-
ments are to be expected or desirable. Also, it is of interest to see what the impact of soil classiÝcation
has been on pedology, which is described here as the study of soils in the broadest sense, and how,
in turn, pedological studies have shaped soil classiÝcation.
In this paper we argue that soil classiÝcation appears to have lost its original links with soil
survey, as expressed by relations between soils and landscapes, and by independent Ýeld observa-
tions by surveyors who were in touch with a wide variety of land users. This observation is relevant
as we face developments in regional land-use studies involving many new forms of interaction with
different types of stakeholders (e.g., Bouma, 2001). Given such developments, in what way can
soil classiÝcation still contribute to the effective communication of soil expertise to a wide variety
of soil users, including not only farmers, contractors, and sanitarians, but also planners, politicians,
and involved citizens?
Developments in plant and animal taxonomy are relevant to soil science. Attention from these
professions has moved from static taxonomy to studies of dynamic processes and, lately, to genetic
engineering, which is now providing a major thrust to biological work, making it the hottest area
in science. This happened because funding for taxonomic studies was difÝcult to obtain even though
taxonomies were far from complete. In soil science, there is a corresponding analogy in terms of
a shift from static classiÝcation to process studies, while genetic modiÝcation of soils has, of course,
as yet no practical signiÝcance. The closest analogy is the effect of soil management on soil
properties, which is characteristically different for different soils.
Soil classiÝcation systems will never be completed, because our increasing knowledge about
soil processes is reÞected in these systems. There is good reason, however, to temporarily stop
modifying systems at this time, because classiÝcation activities tend to become rather self-centered
and inward-looking. Emphasis on dynamic process-studies of soils in a landscape context and on
assessing the effects of soil management deserves priority now to broaden our insights which, in
time, can and should be the basis for further development of taxonomic systems.
SOIL CLASSIFICATION AS A PURPOSE IN ITSELF
For many decades, soil classiÝcation has been a separate object of study within soil science.
Development of a universally accepted classiÝcation system was a worthwhile objective requiring
a lot of data, particularly that derived from chemical and mineralogical studies. All scientists who
were involved with pedological studies that had a focus on soil classiÝcation remember Ýeld
