Soil Report - Agriculture et Agroalimentaire Canada

A vertical section through the exposes a characteristic
sequence of soil horizons that is called a soil profile . These
soil horizons are usually designated as A, Band C horizons,
and subdivided further when more detailed descriptions are
required .
Figure 22 shows the soil horizons of a well-drained soil
profile typical of many in the Haldimand-Norfolk Region .
The A horizon is the surface horizon; it can be further
subdivided into an Ap or Ah, andAe horizons (21) . The Ap
and Ah horizons are dark colored and usually have high
organic matter contents. Ap horizons occur where soils
have been cultivated, and usually constitute the topsoil, or
plow layer . Ae horizons are leached, light-colored, and have
lower organic matter contents than Ap or Ah horizons.
Some, or all, of the Ae horizon materials are often incorporated
into the plow layer, especially when plowing is deep, or on
eroded slopes .
B horizons are usally more reddish, finer-textured, and
more compact than A horizons . When they contain
significantly more clay than overlying A horizons they are
called Bt horizons (21) . When they differ from A horizons
mainly by color or structure differences, they are called Bm
horizons (21) . Most well-drained soils in the Haldimand-
Norfolk Region have Bt horizons that are overlain by Ae or
Bin horizons, as shown in Figure 22 . On moderately to
severly eroded slopes, B horizons are often exposed at the
surface .
C horizons underlie B horizons in normal soil profiles
(Figure 22) . They are composed of soil parent material that
has undergone relatively little weathering compared with
the A and B horizons . In the Haldimand-Norfolk region, C
horizons are moderately to strongly calcareous because
they contain free carbonates . They are called Ck horizons
because these carbonates exhibit visible effervescence when
contacted with dilute hydrochloric acid (21) . If the texture
or origin of C horizons is significantly different from that of
overlyingA or B horizons, e.g. lacustrine sand over clay till,
the C horizon is designated as a IIC horizon . C horizons are
usually exposedonly on roadcuts or on certain severely eroded,
slopes.
Imperfectly drained soils have the same type and sequence
of horizons as well-drained soils, but because they are wetter
for longer periods of time, "gley" conditions develop . These
conditions are mainly caused by the reduction of iron
compounds, and are usually indicated by yellowish-brown
mottling in the Ae, Bm or Bt horizons . The horizons are then
designated as Aegj, Bmgj and Btgj horizons (21) .
Most poorly drained mineral soils in the Haldimand-
Norfolk Region have soil horizon sequences similar to that
shown in Figure 23 . These soils are wet for long periods of
time, providing conditions that are especially favorable for
"gley" formation . This means that all horizons are gray to
grayish-brown in color, and often have yellowish-brown
mottles. The B and C horizons of these poorly drained
profiles are usually designated as Bg and Ckg horizons .
There are some very poorly drained organic soils in the
region that have more than 40 cm .ofsurface organic soil, and
contain at least 30% of organic matter. Horizons of organic
soils are called O horizons . Different lowercase suffixes are
used, e.g . Oh, Om, Of, depending on the degree of decomposition
of the organic materials (21) .
The highest category of soil classification in the Canadian
system of soil classification is the order . Orders are subdivided
into great group, great groups into subgroups, subgroups
into families, families into series and series into phases (21) .
- Ap horizon (very dark gray)
- Bg1 horizon (mottled grayish brown)
- Bg2 horizon (mottled grayish brown)
- Ckg horizon (mottled light brownish gray)
Figure 23 . Diagrammatic soil profile of a typical poorly
drained soil in the Haldimand-Norfolk Region
Soil Orders
Soil orders that have been noted in the Haldimand-
Norfolk Region are the Luvisolic, Brunisolic, Gleysolic,
Regosolic and Organic orders .
Most well and imperfectly drained soils in the Region
have been classified in the Luvisolic order . They are
characterized by light-colored eluvial horizons, and darker
colored illuvial B horizons in which clay has accumulated .
Soils of the Brunisolic order, which lack the same degree
of horizon development as Luvisols, are fairly common in
the Haldimand-Norfolk Region . They seem to be most
prevalent in some imperfectly drained soils, and in soils that
are relatively young in age, such as alluvial floodplain soils
and eolian sands.
Most poorly drained soils in the region were classified in
the Gleysolic order . These soils are associated with high
groundwater conditions during some period of the year . In
the heavier clay soils, groundwater frequently occurs as
disconnected lenses. Such groundwater lenses commonly
"perch" on relatively impermeable lower horizons. These
soils have at least one gray or grayish-brown gley horizon,
and usuallyhave prominent mottleswithin 50 cm of the surface.
Soils belonging to the Regosolic order occur throughout
the region on small, localized areas of severely eroded
slopes, colluvial depressions and alluvial floodplains . They
are characterized by weak or absent soil horizondevelopment.
Soils of the Organic order are saturated by water for '
prolonged periods of time. They are characterized by high
proportions of organic matter and a minimum thickness of
40 cm of organic materials . They were mapped in relatively
few depressional areas in the region.
Soil Great Groups and Subgroups
In the Haldimand-Norfolk Region, soils that belong to the
Luvisolic order are classified in the Gray Brown Luvisol
great group. Well-drained soils of this great group can be
classified into the OrthicGray Brown Luvisol subgroup and
the Brunisolic Gray Brown Luvisol subgroup. Imperfectly
drained soils are classified in the Gleyed Gray Brown