Soils of the - Agriculture and Agri-Food Canada

CHAPTER TWO
SOIL CLASSIFICATION AND FIELD MAPPING METHOD S
This chapter discusses briefly the rationale of soil classification, the soil characteristics considered and th e
various levels of generalization in the hierarchy of the Canadian soil classification system . It also describes th e
field methods and procedures employed during the survey of the Langley-Vancouver map area .
SOIL CLASSIFICATIO N
Soil is the naturally occurring unconsolidated mineral or organic material at the earth's surface which i s
capable of supporting plant growth . It develops in response to the environment . The kind of soil produced is a
function of climate, biota, topography and soil parent material (surficial geologic deposits) reacting interdepen -
dently over a period of time .
Each soil produced is a three-dimensional, naturally occuring body having length, width and depth . Th e
objective of a soil survey is to identify the different kinds of soil produced, to separate or classify them by mean s
of a classification system and to delineate their areal distribution on a map. Soils are classified on morphologica l
characteristics observed in a vertical section (soil profile) and on the physical and chemical analysis of the soi l
pedon . Individual soil profiles are grouped (classified) according to categories of the soil classificatio n
employed . The resultant different groups are then delineated on the soil map by soil boundaries whic h
encompass areas of soil in the same group . The kinds of morphologic characteristics considered are discusse d
in the following section dealing with field methods .
The basic soil mapping unit or category is the soil series . A soil series consists of a group of related pedon s
derived from a similar kind of soil parent material which have soil profiles, textures, and soil moisture characteris -
tics that fall within a narrow, defined range . Soil series names are usually place names occurring in the localit y
where the series was originally classified . The series, however, is not restricted to that locality only .
Soil phases are variations within a soil series or other hierarchial category due to stoniness, topography ,
depth of profile or other features which effect land use . Sometimes soil variants are employed when differin g
soils are identified but occupy such small areas that definition of a new soil is not warranted . These areas are
usually classified as a variant of the established soil series (or other category) which has most characteristics i n
common with the variant .
The first level of generalization above the soil series is the soil family. A soil family consists of a group o f
related soils which fall within a range of differentiating criteria that is broader than that for soil series . Th e
differentiating criteria include particle size distribution, drainage, permeability, reaction and consistence a s
well as others that have implications for land use . A soil series should not be classified in more than one soi l
family.
The next level of generalization is the soil subgroup. A soil subgroup consists of a group of soils which have
defined common soil horizons which reflect the environmental conditions under which the soils developed . Soi l
subgroups may be grouped into soil great groups . Soil great groups consist of soils which have major soi l
horizons in common which reflect the strength of the dominant soil forming process (or processes) . Th e
broadest level of generalization is the soil order. A soil order is composed of groups of soils that have develope d
under broadly similar environmental conditions as expressed by the presence (or absence) of major, diagnosti c
soil horizons .
Fora complete description of the soil classification used in this report, refer to the Canadian System of Soi l
Classification, 1978 and The System of Soil Classification for Canada, 1974, revised .
FIELD METHODS AND PROCEDURE S
As earlier stated, the purpose of a soil survey is to delineate on a map the distribution of classified soils . I n
conjunction with the maps, a report is usually produced which describes the nature and properties of th e
classified soils . The report may also contain interpretations for various specified soil uses .
The level of soil classification employed in the Langley-Vancouver map area is basically the soil series ,
particularly for lands in the Lower Fraser Valley (Volume 1) of this report . In the mountainous areas (Volume 2) ,
the classification approaches the soil family level due to lower survey intensity and somewhat less precise fiel d
data in the more inaccessible areas .
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