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SOUTHEASTER! GEOGRAPHER Volume III 1963 THE NEW SOIL CLASSIFICATION SYSTEM AND GEOGRAPHIC METHODOLOGY R o b e r t W. P e p l ie s East Tennessee State University American soil scientists are about to embark into a new era of soil classification and mapping. The new program instigated by the Soil Conservation Service, will affect everyone engaged in soil work from thè university pedologist to the soil surveyor in the field. Changes have already taken place with respect to soil pedagogy in the colleges, and Survey personnel are being prepared for the new program which should be fully operative by the summer of 1964. The modification that soil science is undergoing presently is largely the result of a new soil classi­ fication which is known currently as “ Soil Classification, 7th Approxima­ tion,” or simply the “ 7th Approximation”. The original purpose behind the development of the new system was to construct a classification that could serve the needs of the Soil Survey better than the previous and present existing systems.1 In particular, the Survey desired a classification device that was organized to perform the following functions. (1) It must allow for prediction about soil behavior, (2) It must be applicable to all soils, whether they are present within or outside the United States. (3) It must be organized to consider, typologically , all soils, and not just those soils which fit into preconceived classes.2 It is obvious that all of these are interrelated. To accomplish these principal tasks, the Survey has incorporated several features that are different from the system now in use.3 Briefly, the major differences between the old and new systems, are as follows.4 (1) All soils are classified in terms of soil properties and not according to genetic agents or factors. (2) A soil class within the 7th Approximation is identified and differentiated from other classes in terms of a norm or central concept (epitome profile) which has defined limits. (3) Soils, in the new system, are recognized in terms of properties that exist within the soil today and are not categorized according to virgin soil properties 1 or the appearance of a predicted soil landscape. It is noteworthy that in the new system stress is placed on soil properties that are the result of man’s activities. (4) A uniform system of nomenclature has been proposed that will allow for better communication among persons in­ terested in the soil phenomenon. The nomenclature uses terms derived largely from Greek and Latin; the names are easily remembered and, most important, identify soil properties of the named soil class. (5) In the 7th Approximation a new category was added— the subgroup. The function of the subgroup is to classify those soils that have properties that are divided among the classes of the higher levels of abstraction (especially the great group). Naturally the central concept of the great group category is included in the subgroup category. In addition, the new system’s frame of reference to “a soil” is based on the assumption that a soil individual is three-dimensional. It consists of one or more pedons and is bounded by “not soils” or pedons of unlike characteristics.y Although the former system employed, essentially, the same approach, the notion of a soil as a three-dimensional object was never clearly defined and specified.6 The pedon concept, even though it is a man-made abstraction, should remove any ambiguity concerning the nature and scope of a soil individual. Although it is not the purpose of this article to explain the new soil classification, a brief discussion is undertaken to note some of the more salient features of the various categories and their identification.7 Six levels of abstraction (categories) are utilized. In descending rank they are called order, suborder, great group, sub group, family, and series. The highest category, the soil order, is divided into ten classes, (see Table 1). The classes are differentiated largely in terms of generalization of common properties associated with degrees of development of soil horizons. Forty classes constitute the suborder grouping, and several differentiae are used to define the classes of this grouping, but the most important criteria are morphological...


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