Semi-detailed Soil Survey of the LIuidas Vale Area, St. Catherine-St ...

THE SOILS
For instance the concept of a certain taxonomic unit may require shallow
soils over limestone rock. Then the range in soil depth allowed within that
taxonomic unit is from 25 to 50 cm.
The most comprehensive taxonomic classification system available to date is
the USDA Soil Taxonomy (Soil Survey Staff 1975 and 1987). This system has
been used by the staff of the RPPD since 1978.
The USDA Soil Taxonomy presents the following advantages:
- it enables an understanding of the relationships between soils and their
environment, thus allowing for the comparison or transfer of knowledge
between similar geographical locations, both nationally and internationally
- it can be used to distinguish well defined mapping units during the survey
- it provides a basis for the interpretation of soil data for selected kinds of
land use (i.e. land evaluation).
4.2.2 The use of USDA Soil Taxonomy in Jamaica
The USDA Soil Taxonomy is a hierarchical system in that units at the highest
level of generalization are subdivided into more detailed sub-units, which
are in turn further subdivided and so on. The hierarchical sequence in the
successive categories from high to low is as follows:
ORDERS-SUBORDERS-GREAT GROUPS-SUBGROUPS-FAMILIES-SERIES.
The grouping of soils in a specific unit at each level is based on combinations
of relatively permanent diagnostic soil characteristics, whose occurrence and
range can be established by relatively simple measurements and
observations in the field and laboratory (e.g. texture, colour, soil reaction,
depth to bedrock, soil temperature, cation exchange capacity, organic carbon
content). From the level of the orders down to that of the series the
diagnostic characteristics become more narrowly defined.
ORDERS consist of soils with similar properties, resulting from the same soil
forming processes, which acted to the same degree on the parent material or
rock. Six out of the ten orders that are recognized by Soil Taxonomy have
been identified in the Lluidas Vale survey. The dominant, generalized
characteristics of these orders are briefly discussed so as to enhance the
user's understanding of the technical classification which is used in Subchapter
4.5 in the description of the soil mapping units. All details are
explained in the Keys to Soil Taxonomy (Soil Survey Staff 1987).
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