GUELPH, ONTARIO - Agriculture and Agri-Food Canada

P,4RT III
THE CLASSIFICATION AND DESCRIPTION OF
BRUCE COUNTY SOILS
The characteristics of the soil depend on certain factors which cause soil
differences. The more important of these factors are: (1) the physical and
mineralogical composition of the parent material, (2) the climate occurring
since the accumulation of the parent material, (3) the plant and animal life
in the soil, (4) the relief, and (5) the length of time these factors have acted
on the material. During the process of formation there have developed in the
soil different layers which can be observed in a vertical cross section of the
soil to a depth of about three feet. This cross section, including part of the
underlying parent material, is referred to as the soil profile and the individual
layers are called horizons of the profile. In Bruce County the kind and number
of horizons found in the soil profile and the sequence in which they occur vary
greatly among the different soils.
Three distinct kinds of profile occur in the Bruce County area, each representing
what is called a Great Soil Group. Soils characteristic of the Grey-
Brown Podzolic, Brown Forest and the Dark Grey Gleisolic Great Soil Groups
are dominant in the County.
The Grey-Brown Podzolic soils are the dominant well drained soils in the area.
They have developed from calcareous materials and have the following profile
characteristics. Under forest they may have a layer of partially decomposed
litter from deciduous trees. The surface soil (A1 horizon) is generally 3 to 4
inches thick, is dark greyish brown to very dark brown in colour, moderately
friable, slightly to moderately acid and moderately high in organic matter.
This horizon consists of a close mixture of mineral and organic materials. The
surface or A1 horizon is underlain by a yellowish brown, pale brown or brownish
grey A2 horizon which is comparatively low in organic matter and slightly to
moderately acid in reaction. The thickness of the AZ horizons may vary considerably
in different soils. In the medium and coarse textured soils the upper
part of the Az horizon is more intensely coloured and is designated as the AZ1
horizon, while the lower more greyish part is designated as the AZ2 horizon.
Under the AZ horizon lies the B horizon. This layer is darker brown in
colour than the AZ and it contains more clay and sesquioxides than any other
horizon in the profile. It is generally slightly acid to neutral in reaction. The
B horizon may be subdivided into a transitional subhorizon to the AZ which is
designated as the B1 horizon and the main or B2 horizon which contains most
of clay and sesquioxides which have been leached from the A horizons. The
B horizon rests upon the unaltered or only slightly weathered calcareous parent
material. The following is a generalized profile description of a Grey-Brown
Podzolic Soil :
A,, - Accumulated layer of partially decomposed litter
from deciduous trees.
AI - Dark greyish brown to a very dark brown mineralized
humus layer.
Azl- Dark yellow-brown layer.
Azz- Pale brown layer.
Bz - Dark brown layer.
C - Light greyish brown calcareous parent material.
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