The Soils of The Regional Municipality of Ottawa=Carleton

adequate moisture or a wetness limitation(imperfect to poorly
drained) . Uniformity of plant growth is affected in these
instances . Limitations V and V are never applied along with
W', W M', or M because those limitations adequately downgrade
map units having soil moisture excesses or deficiencies .
(2) LimitationsNot Affecting the Rating
Occasionally, limitations may be present and shown in
someratings which have not been allowed toinfluence the class
designation, although they may do so in other ratings . Brack
ets are placed around these limitations which are minor in
terms of severity and occur in Class 1 to 5 ratings . One of the
following reasons may applytolimitations givenin this way :
they may represent a potential limitation which may not
occur consistently, i .e., moisture deficiency (m) applied
when depth to impermeable substratum is highly variable.
they may represent a benefit rather than a limitation . For
example, when the secondary drainage component of a
map unit is better drained than the main component, the
potential benefit to crop growth of the better drained secondary
component is recognized with subclass symbol (v)
but it is ignored in the overall assessment of limitations to
arrive at the capability class . This is the case for most (v)
limitations shownin the ratings .
they are not severe enough to warrant downgrading some
soils further than that indicated by the other limitations
which are present, for example, (t) in some ratings.
(3) AssociatedStoniness
in some soils, stones are present in significant amounts in
the material itself and will pose a continual hindrance to
annual cultivation even after normal stone removal . Stoniness
limitations in some ratings, therefore, may reflect this inherent
or residual stone content and not the surface stoniness . One
example of associated stoniness occurs in the Farmington soil
association where a moderate stoniness limitation P rather
than minor limitationp is applied to soils with Stoniness Class
l (SI) .
(4)Limitations Requiring LessSevereDowngrading
When limitations F' and M' are both present, their combineddowngrading
value is three classes ratherthan four, e. g . 4
F'M' . Ifeach were allowed to downgrade two classes, a downgrading
to Class 5 would betoo severe.
(2) Capability Classification forOrganic Soils
The previously described classification system applies
only to the mineral soils in the survey areas and cannot be
applied to the organic soils. A separate classification system
for organic soils is necessary due to their unique physical characteristics
and properties . The system applied in this survey is
based to a great extent on two previously established systems
by Leeson (25) and Hoffman and Acton (26) . Guidelines and
soil parameters of those systems were incorporated into the
system described herein which provides a general assessment
ofa soil's agricultural capability.
In the classification system, organic soils are mainly
assessed for their long-term capability to intensively grow vegetable
crops . It is assumed that substantial costs are associated
with the reclamation ofmost organic soils and that high return
crops such as vegetables will have to be grown . Therefore,
organic soils which do not have long-term capability for vegetable
crop production will have a low agricultural capability.
Soils with this capability include those which are restricted to
producing crops other than vegetable crops, or those which
have no capability for agriculture of any type. In these
instances reclamation or improvement practices are not feasible
due to either economic or physical limitations .
In general the classification system places an organic soil
in one of seven capability classes based on the severity of limitations
which are present . Limitations consist of detrimental
soil characteristics which adversely affect or limit vegetable
crop production .
(a) Organic Soil CapabilityClasses
The capability class consists ofa group of soils which have
the same capability or potential forthe production of vegetable
crops . Class 1 soils have the greatest capability and no limita
tions for the production of vegetable crops . Class 4 soils have
severe limitationsand areonly marginal for vegetable crop production,
while Class 7 soils have no capability for agriculture.
Soils grouped in the same class may have various types of limitations
. However, the degree of severity of the limitations
present in each soil is similar. The soil capability classes are
described as follows :
Class 1 - Organic soils of this class have no water, topographical,
or pH limitations. They are deep and
level and at an intermediate stage of decomposition.
Class 2 - Organic soils in this class have one limitation
which restricts their use in a minor way. The limitation
may be woodiness, reaction, or depth .
Class 3 - Organic soils in this class have moderately severe
limitations that restrict the range of crops, or that
require specialmanagement practices.
Class 4 - Soils in this class have limitations that severely
restrict the range of crops, or require special development
and management practices . Reclamation
and management costs will be high .
Class 5 - Soils of this class have such severe limitations that
they are restricted to the production of crops other
than vegetables . Perennial forage or other spe
cially adapted crops may be grown . Large scale
reclamation is not feasible.
Class 6 - Class 6 organic soils are capable of producing only
indigenous crops consisting of plants which are
native to the area . Improvement practices are not
feasible .
Class 7 - Organic soils in this class have no capability for
agriculture.
(b) Organic SoilCapability Subclasses
A subclass is a group of soils with similar kinds of limitations
or hazards . Four kinds of subclasses or limitations have
been identified, and they are described as follows :
K - Stage of Decomposition - Mesic soils or soils of intermediate
decomposition are the most desirable in order to
avoid water control problems associated with fibric or
humic soils . Since the upper 40 cm of material will
decompose rapidly after only a few years of agricultural
use, the material composing the 40-160 cm depth of the
profile is assessed because it is this material which will
have a continuing effect on the drainage, permeability,