Agriculture Reference
In-Depth Information
17
CHAPTER
Soil Taxonomy and Soil Survey
C.A. Ditzler, R.J. Engel, and Robert J. Ahrens
CONTENTS
Abstract ..........................................................................................................................................221
Introduction ....................................................................................................................................222
Impact of the Use of Quantitative Criteria....................................................................................222
Parity and Consistency in Classifying Soils ........................................................................223
Quantity and Quality of Data Collection.............................................................................223
ReÝnement of Soil Series Concepts ....................................................................................224
Improvement in Soil Correlation .........................................................................................224
Some Problems with Quantitative Limits ............................................................................225
Taxonomic Units and Map Units...................................................................................................225
Soil Individuals.....................................................................................................................226
Taxonomic Purity of Map Units ..........................................................................................227
References ......................................................................................................................................228
ABSTRACT
Soil taxonomy was developed primarily for the practical purpose of supporting the National
Cooperative Soil Survey (NCSS) Program in the United States. It was adopted nearly 40 years ago
by all of the NCSS partners, and is recognized as one of our most important standards. The adoption
of the classiÝcation system had several important impacts on the soil survey program. The emphasis
on observable diagnostic horizons and features for deÝning classes tended to make all competent
soil scientists, regardless of experience and rank, equally capable of accurately and consistently
classifying soils. By focusing attention on qualitative class differentiae, the quantity of Ýeld data
collection has increased and the quality has improved. Property ranges of soil series and their
geographic distribution have generally been narrowed over time, allowing us to make more precise
interpretations. Soil Taxonomy has beneÝted the soil correlation process by grouping the nearly
22,000 series currently established in the United States in ways that allow us to efÝciently compare
and differentiate competing soil series, and coordinate their use among survey areas.
One area that has presented difÝculty and confusion from the beginning of Soil TaxonomyÔs
use has been reconciling the difference between map units and taxonomic units. Our soil maps are
an attempt to depict our understanding of how natural soil bodies occur within the landscape. The
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