Bodemkundige inventarissen : kwaliteit en evaluatie karakterizering, van hun geschiktheid voor specifiek landgebruik / Soil resource inventories : characterization, quality and evaluation of for their adequacy specific land use
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Date
1987
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
State University of Ghent, Belgium
Abstract
In many countries a lot of soil resource inventories (SRIs) particularly soil
surveys have been made and are still being made.
Their objectives are
generally well stipulated and known, yet there are indications that these
documents are not sufficiently being used both in developing and developed
countries.
It is against this background that the present study was started.
The intention has been to look for ways of characterizing SRIs and to evaluate
their adequacy for specified land uses.
This way it was hoped that reasons
behind the limited use of such documents could be identified and hence help to
frame recommendations for future soil inventories.
The data base in this study comprises (a) a total of 176 soil survey reports
(including
accompanying
maps) from 46 countries,
(b)
70
70
completed
questionnaires from soil surveyors representing 40 countries and (c) 94
completed questionnaires from users of soil maps and reports representing 35
countries.
Using the 176 SRIs, a general inventory of the documents was made as a first
attempt to characterize them.
Then indices to characterize the SRIs in terms
of their cartographic attributes were developed.
These indices were highly
correlated with each other.
Other observations on cartographic attributes
indicated that (a) the concept of map linear reduction factors is not
consistently used and (b) information on soil description sites is only rarely
given in SRIs.
In relation to the information content of map legends and soil reports it was
observed that (a) most SRIs are produced by free survey method; (b) the most
commonly used attributes in soil mapping are texture, drainage, landform,
topography, parent material and soil depth; (c) information on density of
field observations is often lacking in SRIs and is commonly vaguely presented;
(d) USDA and FAO/Unesco classification systems are the most widely used
internationally; (e) most SRIs contain interpretive data and (f) information
on purity of mapping units is often not given in SRIs and in many cases only
partly presented.
Two methods are developd and described for estimating the utility of base
maps.
It was noted that many SRIs do not bear information about their
compliance with specified base map accuracy standards.
With regard to general legibility of SRIs, it was observed that (a) provision
of instructions on how to use the SRIs is mostly neglected and (b) glossary of
specialized terminology and ranges of soil properties of mapping units are
commonly not provided in the documents. A method is developed and described for characterizing and systematically
evaluating information given in map legends and soil reports about mapping
units in function of specified land uses. Furthermore, a comprehensive method
is also described for the assessment of the predictive adequacy of SRIs for
three land uses in function of (a) cartographic attributes, (b) map legend and
soil report attributes and (c) base map attributes.
Guidelines outlining the
assessment procedure are provided.
This method was applied on 66 selected
semi-detailed and detailed SRIs from 17 countries.
Following strictly the
stipulated criteria of adequacy it was found that only about 27 « of the
documents are completely adequate for predicting performance of both corn and
oil palm, and about 30 % can be considered adequate for predicting performance
of Eucalyptus deglupta (forestry).
A preliminary study on the adequacy for prediction of soil erosion hazards was
done on 50 selected SRIs from 18 countries,
Based on the adequacy criteria
per se, it was found that most of the documents could be said to be adequate
for the use in question,
It was also noted that (a) although information on
climate is given in all documents, winds are frequently not described; (b)
information on topography is normally limited by the lack of contour lines
printed with soils information or the lack of contour maps appended to the
soil maps and (c) information on soil permeability is often not described.
Analysis on the answers given by respondents of the questionnaire to soil
surveyors shows that (a) soil surveyors to a great extent determine the nature
of SRIs to be made and only occasionally do users have the opportunity to do
so; (b) some terminologies and criteria used in soil survey eg. soil survey
intensity, field soil mapping procedures and purity of mapping units are not
conceived and used consistently; (c) most soil surveyors do not monitor
utility of the SRIs they make; (d) soil maps are sometimes too complicated and
(e) publicity about SRIs has not sufficiently been made.
The results from the questionnaire to users of soil maps and reports indicate
among other things that (a) soil surveys are still considered very important
in development projects; (b) there are problems of knowing about the existence
of soil maps, yet communication media such as radio, television and newspapers
have not been used significantly to ameliorate the situation; (c) major
problems
encountered while using soil maps and reports include
poor
legibility, problems of location on the maps, use of vague and in some cases
complicated terminology,
A revised questionnaire to users of soil maps and
reports has been proposed to accomodate changes that will take it more useful
as a source of information.
To put everything in a nutshell, it can be said that indeed, existing SRIs do
present serious bottlenecks that need attention in future inventories.
For
this a series of recommendations has been suggested at various levels of the
study.
Description
Thesis
Keywords
Soil resources, Soil surveys, Soil