02 Contents Frame

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Chapter 2
Historical development
Three historical periods can be distinguished in the development of land evaluation: 
before the Framework for land evaluation (FAO 1976); the period largely influenced 
by the Framework; and the period with recent developments.
LAND EVALUATION AND CLASSIFICATION BEFORE THE FRAMEWORK
Before the Framework, the most widely known land classification system was the 
USDA Land Capability Classification (LCC, Klingebiel and Montgomery 1961). 
The purpose of LCC was to advise farmers on the most appropriate use of their 
fields. Soil mapping units were classified in eight classes according to their ability to 
support general kinds of land use without degradation or significant off-site effects. 
The first four classes are arable land, in which the limitations on the use and need for 
conservation measures and careful management increase with class number (Helms 
1992). The remaining four classes are not suitable for cropland, but may have uses for 
pasture, woodland, grazing, wildlife, recreation and other purposes. Within the broad 
classes, subclasses signify special limitations such as erosion, excess wetness, problems 
in the rooting zone, and climatic limitations. Within the subclasses, capability units 
give some indication of expected yields and management needs. The capability units 
are groupings of soils that have common responses to pasture and crop plants under 
similar systems of farming but requiring different management. Units are defined 
locally for each survey and described in detail, which make the system applicable to 
local situations. Although indicative for local soil use and management, LCC only 
considers relatively permanent, static land characteristics and does not take into 
account socio-economic factors. The system provided a general appraisal, and did not 
assess capability separately for each kind of land use. It relied on an ordering of kinds 
of use in a implied order of desirability, with agriculture preferred over forestry, and 
both over wildlife conservation.
Map units from soil surveys are commonly interpreted directly for anticipated 
uses. The classification is based on relatively permanent soil characteristics and results 
directly in suitability classes for the envisaged use. Examples include engineering 
applications (Olson 1981). Special-purpose soil surveys may be conducted to determine 
soil suitability in cases of pre-determined land use such as irrigation developments or 
plantation agriculture (Dent and Young 1981). Such studies were often referred to as 
soil survey interpretation, and many of them constituted valuable early work on what 
was in fact land evaluation. 
Surveys for irrigation development take an engineering approach to plan the location 
of major and minor irrigation and drainage works. The enormous costs involved justify 
a comprehensive appraisal of land suitability, which usually includes biophysical and 
economic aspects, e.g. the USBR land classification for irrigation (USBR 1951). The 
system does not use a rigid or fixed methodology. Instead general principles are applied 
to fit land classification to the economic, social, physical and legal conditions existing 
in a project area. The classification is quantitative, with an emphasis on economic 
appraisal. The system uses six classes. Four classes are suitable for surface irrigation, 
one is potentially suitable and one class is unsuitable. The USBR system heavily 
influenced the Framework, especially the idea that only economic considerations can 
truly classify land for development projects.

Land evaluation – towards a revised framework
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Factorial approaches to land suitability provide a single numerical index derived 
from addition, multiplication or normalization of component factors. The misleading 
pseudo-accuracy of one numerical value often masks methodological problems such 
as how to weight and combine individual factors into a single scale, or the subjective 
expert judgment of individual weightings and dependencies. Examples are the 
Californian Storie index (Storie 1933), which ranks agricultural land for purposes of 
taxation, and the productivity index (Riquier et al., 1970), which multiplies nine factors 
based on soil characteristics that are correlated with yield. 

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