Agriculture Reference
In-Depth Information
EVOLUTION OF CONCEPTS
The Dawn of Soil Classification
When Dokuchaev (1896) formalized his concept of soils and the Russian classiÝcation, it
became a benchmark event in soil science, marking the starting point of a new science. The basic
concepts he enunciated inÞuenced developments in soil classiÝcation, and elements of his concepts
and principles are integral parts of modern classiÝcation efforts. The importance of soil moisture
in determining soil attributes was emphasized by Vysotskii (1906), and the notion of soil zonality
was born. The role of climate was further elaborated by Lang (1922), who also considered tem-
perature, and perhaps is one of the Ýrst to recognize soils in the tropics as a separate set of soils.
This was another major step in the development as aspects of this principle became incorporated
into other classiÝcation systems, including Soil Taxonomy (Soil Survey Staff, 1999).
By the time of the Ýrst International Congress of Soil Science in 1924 in Washington, DC, the
climatic aspects were reÝned. Because of the difÝculties of acceptable climatic parameters, soil
cover was used as differentiae (Afanasev, 1928). By this time, two large groups of soils in the
tropics were known: the red soils and the black soils. The red colors and the deep weathering
proÝles of many soils in the tropics are distinctive, and most of the earlier classiÝcation systems
in the world differentiate these soils from the soils of temperate regions, which have good horizo-
nation and generally do not exceed a meter in thickness. Traditionally, there has also been a tendency
to view the soils of the tropics differently from the colder temperate region soils. The vegetation
and land use were additional reasons for making this distinction.
The highly weathered soils of the tropics were grouped under red soil, red loam, or red earth
until about the middle of the last century. Among others, the work of Kubina (1953) inÞuenced
the thinking of the period. Kubina was already working with soil micromorphological analysis
and developed his ÑErde and LehmÒ concepts, which did not have much acceptance among the
soil scientists who were more familiar with physical and chemical properties. These concepts were
the basis for the later differentiation between argillic and cambic horizons. With the description of
laterites by Buchanan (Buchanan, 1807), the term
(and lateritic soils) became prevalent in
the soils literature (Alexander and Cady, 1962). With more studies, other adjectives were added to
the term
laterite
(Cline, 1975) that
soon became very popular (Bennema et al., 1959) despite the fact that it was not deÝned in rigid
terms. In the soil survey of Hawaii, the terms Humic Latosols, Hydrol-humic Latosols, etc. were
used (Cline et al., 1955). This was also the period when the concept of Ñpodzolic soilsÒ was being
accepted (Baldwin, 1928; Baldwin et al., 1938) and the Latosols (Kellogg, 1949) were considered
to be a distinct group of soils. In the United States, Thorp and Smith (1949) formalized this state
of soil classiÝcation after the war, but difÝculties in the use of the system and the rapid increase
in information required the development of new concepts and approaches. Dr. Guy D. Smith was
charged by the Soil Conservation Service of USDA to develop a new system, which today is known
as Soil Taxonomy. In the 1950s and 1960s, several other classiÝcation systems became in vogue,
and other terms to describe these highly weathered soils of the tropics were coined.
By about the mid-1950s, the concept of Latosols as highly weathered or low negatively charged
soils became Ýrmly established, and paved the way for the modern concept of Oxisols. The decade
of the 1950s also saw great advances in mineralogical studies, and with increasing studies on soils
of the tropics, the processes responsible for Latosol formation were better understood. The 1950s
perhaps mark the second renaissance of pedology, launched by several events or factors. First were
aspirations to develop national classiÝcation systems. More important, however, was the decision
of the Food and Agricultural Organization of the United Nations to embark on a ÑSoil Map of the
WorldÒ program. During this period, the term
lateritic soils.
In 1949, a group of scientists created the term
Latosol
Ferralitic Soils
appeared in the French (Aubert, 1958)
