Agriculture Reference
In-Depth Information
ClassiÝcation systems portray the state of knowledge of the science, but as Smith (1965) has
warned, they can become a potent factor limiting the possibilities of new experience. Smith states:
If its criteria are theories without some device for constant and inescapable scrutiny in relation to
fact, the concepts in the system become accepted as fact. Such acceptance can mold research expe-
rience into patterns of the past and can limit understanding of even new experience to concepts
established in the past.
As Soil Taxonomy evolved from previous systems, it inherited many useful notions, but also
became entrapped in accepted concepts of a previous era from which it has become extremely
difÝcult to dissociate itself. Guy Smith recognized this difÝculty, as he was confronted with
formidable obstacles when he tried to make paradigm shifts. At the end of his career and in
retrospect, he conÝded to the authors that, to some extent, he had failed to make those important
changes that he deemed were necessary, but rested with the conÝdence that he had helped develop
a system that will be capable of modiÝcations with new knowledge. He indicated in his interviews
(Forbes, 1986) that if a system is not Þexible when challenged by new knowledge, it is a mark of
failure of the system. In this respect, it is evident that soil classiÝcation systems are a series of
approximations that must be continuously evaluated and modiÝed for a changing knowledge base
and the needs of society.
ISSUES OF CONCERN
More than 25 years have passed since the Ýrst edition of Soil Taxonomy. With the advent of
Soil Taxonomy and the acceptance of many of its concepts and terminology, modern soil surveys
have been conducted with a better scientiÝc basis. In the last quarter-century, many countries have
published national soil maps with supporting data, and many have also commenced detailed
mapping supported with pedological studies. The cumulative effect of this progress is that some
concepts have been questioned and many new proposals have been formulated. These have been
reported at scientiÝc meetings or as technical papers in journals. The authors have also had the
opportunity to discuss them with scientists in their countries. Some of the major issues are presented
here.
Inconsistencies in the system may be inherent or introduced consequent to changes made to
parts of the system. A change in one part of the system may have repercussions across the system.
These require time and effort to locate and correct, and are an ongoing task of the Soil Survey
Staff. The change in deÝnition of the Vertisols and the introduction of a suborder of Aquerts are
examples that are discussed later. Those inherent in the system are usually those inherited during
the development of the system, and there is a general reluctance to change them. Mollisols with
aridic soil moisture regime is an example.
Some changes were introduced without adequate testing and evaluation of the consequences.
The change in the deÝnition of the ÑisoÒ soil temperature regime is a case in question, and reÞects
the situation in which the process for accepting changes was violated. Other examples of changes
that were introduced result from compromises among well-meaning scientists. The introduction of
the Ñkandi conceptÒ is an example. The concept, as elaborated later, not only violated the principles
of the Soil Taxonomy (Cline, 1949, 1963), but was also not a major improvement to the system.
Finally, there are examples of situations in which an absence of detailed studies has prevented
an acceptable consensus on the subject. Rice-growing soils of the tropics is a good example. Such
soils were not included in the effort of SMSS, and little has been done by NRCS since the
termination of SMSS. The problems of seasonally Þooded soils, as elaborated later, are not only
one of classiÝcation but have relevance to larger questions of soil management and global warming.
