Soil Report - Agriculture et Agroalimentaire Canada

'Supplemental irrigation is assumed forflue-cured tobacco on all soils, so the suitability ratings for this crop will not change from
application of the irrigation managementfactor.
'It should be recognized that these management guidelines are only approximate because of insufficient data . Responses may be
somewhat greater or lesser for certain crops than indicated. Also, under unfavorable climatic conditions, some additional soils may
respond favorably to artificial drainage or irrigation .
Table 13 . Decrease in land suitability ratings for special
crops according to slope group*
Slope groups
B C,c D,d E,e F,f,G,g
Crop subgroup (0-2%) (2-5%) (5-9%) (9-15%) ( >15%)
Al 0 0 -1 -2 -3
A2 0 0 -1 -2 -3
A3 0 0 -1 -2 -3
A4 0 0 -1 -2 -3
B1 0 -1 -1 -2 -3
B2 -ginseng 0 0 0 -1 -2
-melons 0 0 -1 -2 -3
B3 -peppers 0 -1 -1 -2 -3
-other crops 0 0 -1 -2 -3
Cl 0 -1 -1 -2 -3
C2 - green beans, 0 - 1 - 1 -2 -3
peas
-pumpkins, 0 0 -1 -2 -3
squash
C3 0 -1 -1 -2 -3
C4 - cucumbers 0 0 -1 -2 -3
-lettuce, 0 -1 -1 -2 -3
radish
D1 0 0 0 -1 -2
D2 0 0 0 -1 -2
D3 0 0 -1 -2 -3
D4 0 0 0 -1 -2
.g. if the suitability rating for crop subgroup A1, e .g .
asparagus, was good (G), for a particular soil, it
would decrease to fair to good (F-G), on a D(5-9%)
slope.
C . SOIL EROSION INTERPRETATIONS
byG.J. Wall, Pedologist, Agriculture Canada, Ontario Institute
of Pedology, Guelph ; J.W. Greuel, and I.J. Shelton,
Research Associates, Agriculture Canada, Ontario Institute
of Pedology, Guelph .
(a) SOIL INTERPRETATIONSFORWATEREROSION
(1) Introduction
Soil erosion by water is a naturally occurring process that
can be greatly accelerated by man's activity . Any practice
that accelerates soil runoff, or reduces the natural protection
afforded by vegetative cover, will generally lead to increasing
erosion levels . It is commonly held that soil erosion reduces
production potential, depletes nutrients, and degrades soil
tilth . However, recent studies in the Canadian Great Lakes
basin have illustrated the need to look beyond the on-site
effects of soil erosion and consider the role of sediments,
derived from cropland, on water quality . Any comprehensive
soil conservation program will recognize the dual nature of
the problem of soil erosion by water.
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The purpose of this section is to provide interpretations of
the erosion potential of the Haldimand-Norfolk Region soils
and soil landscapes . Specifically, the objectives may be
summarized as follows :
(a) to determine the relative erodibility of surficial soil
materials;
(b) to determine the effect of soil erodibility and slope on
soil erosion potential;
(c) to provide information on the effects of different crops
and associated cropping practices on soil erosion potential ;
(d) to illustrate how the soil maps, in combination with
information from the report, can be used to assess sitespecific
soil erosion problems and alternative solutions ;
(e) to provide guidelines for estimating soil erosion potential
at the regional scale .
(2) Factors Affecting Soil Erosion by Water
On-site planning for soil and water conservation requires
information on the relationship between factors that cause
soil erosion, and practices that may reduce soil erosion . The
most important factors affecting agricultural erosion are
usually considered to be rainfall runoff, soil erodibility,
slope gradient and length, and vegetative cover .
Both rainfall and runoff parameters must be considered in
the assessment of a water erosion problem . Rainfall-induced
erosion is maximum when the energy of the rainfall is
greatest . In Ontario, it is the high-intensity, short-duration
thunderstorm activity of the summer months that produces
the highest-energy rainfall events . On the other hand, runoff
from agricultural land is greatest during the spring months
when the soils are usually saturated, the snow is melting, and
evapotranspiration is minimal . A good soil and water management
program must address itself to rainfall and runoff
problems, in both the spring and the summer periods .
Soil erodibility is defined as the inherent susceptibility of a
soil material to erode . Soil properties that influence erodibility
by waterare those that affect the infiltration rate, permeability
and water-holding capacity of the soil . Soil properties that
resist the dispersion, splashing, abrasion and transporting
forces of rainfall and runoff, also influence soil erodibility .
Silt, silt loam and very fine sand soils often have the greatest
soil erodibility potential, whereas sandy and clayey soils
usually have the least inherent soil erodibility . Maintenance
of soil organic matter and soil structure, through good soil
management, can greatly affect soil erodibility potentials .
Soil erosion by water has been found to increase, with
both increasing slope gradients and slope lengths . Steep
slopes facilitate the runoff of water and reduce the infiltration
of water . The potential for erosion on long slopes is
enhanced by rapid and voluminous runoff which can generate
high erosive energy at downslope positions. Hence the
effective slope length should be an important soil conservation
consideration in farm field consolidation efforts.
The effect of vegetative cover or mulches, in reducing
soil erosion, is well known. Table 14 illustrates the relative
effectiveness of common field crops in reducing water
erosion potential in Ontario. If unvegetated or bare soil is
assigned a numerical value of 1.0, then the vegetative cover
afforded by bean, tomato, or cucumber crops has the
potential to reduce water erosion by approximately 50%
(Table 14) . Similarly, a hay-pasture or permanent pasture