The Soils of The Regional Municipality of Ottawa=Carleton

capillary rise of water, and rate of subsidence of the profile
(25) . Organic soils inthe survey areas were, therefore,
classified based on their stage of decomposition at the
40-160cm depth ofthe profile in the following way :
Dominant Material Capability Class
Fibric-poorly decomposed Class 4
Humic-well decomposed Class 3
Mesic-moderately decomposed Class 1
Note : Humic or Fibric materials in combination with
other limitations may further downgrade the capability
rating of some soils .
F - Reaction-The fertility level oforganic soils is generally
low and considerable fertilization will be required for the
production ofvegetable crops . Soil reaction, however, is
an important consideration when assessing organic soils
as a growth medium for such crops. Most plant roots will
not grow into a highly acid medium, while others do not
tolerate alkaline conditions . Organic soils in the survey
area weretherefore classified on the following criteria :
Reaction CapabilityClass
pH 4 .5 - 7 .0 Class 1
pH 4 .5 - 4 .0 Class 2
pH 4 .0-3.5 Class 3
L - Wood Content - Large pieces of wood such as tree
trunks, stumps, or branches will probably interfere with
cultivation, ditching, or the installation of tile drains .
Wood in general also affects the moisture regime of the
soil . When large pieces occur within the upper 60 cm of
the profile, they will affect cultivation practices within
the first fewyears of agricultural use. Periodic removal of
wood fragments may, therefore, be necessary . Organic
soils have been classified on the basis of the volume of
wood occurring in relation to the total volume of material
in the control section . The following ranges in wood
content were used for classifying the soils in the survey
area :
Wood Content Capability Class
(Percentof total volume)
None Class 1
1-25% Class 2
26-50% Class 3
> 50% Class 4 or lower
H -Depth of organic material over type of substratum -
Due to subsidence associated with agricultural use, a
minimum depth oforganic material must be available in
order to economically justify reclamation . Long-term
agriculture use, therefore, requires a considerable depth
of organic material . When such depths are not present,
underlying mineral material or bedrock occurring close
to the surface will affect the feasibility of subsurface
drainage . In these cases, fine textured mineral substrata
generally present fewer management problems than
medium or coarse textured material or bedrock substrata
. The following criteria for depth and type of substrata
were used to classify the soils :
Capability
Class
Depth of Organic
Material
Class 1 > 160 cm - alltypes
(c) Organic Soil Capability Ratings
Capability ratings for soil landscape units are given in
Table 10 . Most soil landscape units encompass a range of soil
characteristics, the most significant being depth of organic
material over mineral or bedrock substrata . In such units, a
range of limitations are also present which often vary in type
and severity. Consequently, a range of capability ratings is necessary
for those units to reflect the soils which compose them .
Whena range ofcapability ratings is given, these represent the
highest and lowest ratings and not all ratings which may apply.
(3) Capability Classification for Land Type and
Miscellaneous Land Units
The classification system which was applied to determine
the agricultural capability of mineral soils was also applied to
these land units . All land type units and some miscellaneous
land units were classified andgiven a capabilityrating . Units of
the latter type which were not classified include land altered by
man . Included in this grouping are areas of Disturbed Land
(DL), Landfill Sites (LF), Sewage Lagoons (SL), Topsoil
Removal (TR), and Urban Land (U) . Agricultural use of these
areas is either not possible or not feasible due to high reclamation
costs.
Capability classes and subclasses as defined in section (1)
were applied to units which were classified . Many of the subclasses
or limitations defined in that section have been applied .
Capability classes areconfined to classes 4to 7 due to the severity
oflimitations which are present .
(b) Introduction to the Agricultural
Capability Rating Tables
Type of
Substratum
Class 2 130 -160 cm - fine textured
Class 3 100 -130cm - fine textured
130 -160 cm - medium or coarse
textured
Class 4 100 -130cm -medium or coarse
textured
40 -100 cm - fine textured
130 -160 cm -bedrock
Class 5 40 -100 cm - medium or coarse
textured
100 -130 cm -bedrock
Class 6 40 -100 cm -bedrock
When applied to the soil maps, the rating tables (Tables 9,
10 and 11) provide the means of determining the agricultural
capability or capabilities ofthe land area represented by a map
delineation . The landscapes which occur within delineations
are represented by either a simple or compound map unit symbol
on the map . When the components of the symbol are
known the applicable agricultural capabilities can be determined
.