Diagnostic horizons and properties are characterized by a combination of attributes
that reflect widespread, common results of the processes of soil formation (Bridges,
1997) or indicate specific conditions of soil formation. Their features can be observed
or measured, either in the field or the laboratory, and require a minimum or maximum
expression to qualify as diagnostic. In addition, diagnostic horizons require a certain
thickness, thus forming a recognizable layer in the soil.
Diagnostic materials are materials that significantly influence pedogenetic processes or
are indicative of them.
Throughout the following text, references to the RSGs defined in Chapter 4 and the
diagnostic features listed elsehere in this Chapter are shown in italics.