TheImprovement ofTropical and Subtropical Rangelands

SITE EVALUATION 105
dynamics ofan ecoeystem. It is bued, regardless ofthe system, on an
examination of the "typical" soils in an area. In the process of classification,
a number of soil attributes may be considered, including
(but not exclusively) many of those described above. Soil clUlific&o
tion is time-consuming and generally expensive, but it can provide
decision makers with necell!l&ry information for the effective planning
of range improvement activities. Fortunately, many countries have
soil survey departments that can furnish technical assistance for this
purpose.
The selection of a soil classification system to be used in a resource
evaluation program is an important consideration. For instance,
the needs of a project with one objective may be met by
a specific-purpose, site-specific soil classification, whereas an integrated
rural development program requires the use of a generalpurpose
soil classification. An example of the former is an irrigation
project aimed at increasing the production of bananas. In this case,
soil properties important to water management considerations must
be used as differentiating criteria in the development of a specificpurpose
soil classification. On the other hand, a multifaceted rural
development program requires a general-purpose soil classification to
U8e88 the suitability of soils for a variety of uses. In this case, soil
clatBes must be defined by attributes relevant to a wide spectrum of
management goals.
Several general-purpose soil classification schemes have been developed
by different countries to meet their needs. As Smith (1963)
noted, a soil classification scheme developed in a particular country is
biased by the accidents of geology, climate, and the evolution oflife in
that country. Its application in other countries can be problematic.
The FAO/Unesco soil-classification system (Dudal, 1968) and
the U.S. Comprehensive Soil Classification System (Soil Survey Staff,
1975) are now used in many nonindustrialized countries (Conant et
aI., 1983). The FAO/Unesco system attempts to group the soils of
the world. Because of the wide spectrum of soil-forming environments,
groups in this system include considerable variability. On
the other hand, soil taxonomy was developed to facilitate soil survey
in the United States (Smith, 1963). To avoid ambiguity, soil
clatBeS are precisely delimited by chemical and morphological properties.
The rigidity of class boundaries and the need for laboratory
analysis hamper the successful application of soil taxonomy in nonindustrialized
countries. Furthermore, since the current version of