The Rural Voice, 1982-01, Page 19A plow's depth
of topsoil
If you have ever noticed hollows in the
grass under the end of drainpipes, you
have seen the effects of water erosion.
Unless the running water is diffused, the
hollows will become potholes that can scar
a lawn. In farm fields, large scale water
erosion can result in gullies that require
bulldozing before planting or harvesting
can take place. Time, energy and money
requirements on these fields climb while
productivity falls, and irreplaceable top-
soil clogs streams and lakes.
Erosion is a significant problem in
Ontario, and at this University research-
ers are looking for practical solutions.
School of Engineering professor Trevor
Dickinson has recently received a contract
renewal of S69,000 from Supply and
Services Canada, in conjunction with
Agriculture Canada, to continue his farm
research on water erosion.
Erosion is a naturally occurring process
based on factors of rainfall, slope, soil
texture (percentage sand, silt and clay)
and vegetative cover. Most existing
information on erosion comes from studies
of the results of summer rainfall, but in
Canada, the largest amounts of soil
materials move downstream during
spring. Prof. Dickinson's study identifies
the need for new ways of describing the
behavior of spring soils.
Spring rainfall is heavier than summer
rainfall; snowmelt contributes to runoff;
crops are not yet established. Raindrops
fall on bare, partially frozen ground with
tiny explosions, breaking apart crumbs of
soil held together by organic matter. The
resulting silt is fine, compactable, sieve-
like and low in nutrients. Spring soil can
be compared to a sponge lying on
concrete; unable to penetrate the frozen
layer, water and silt flow readily downhill.
As part of Guelph 's study, the research-
ers built a rainfall simulator and a flume
that channels water over soil. Experimen-
tal runs can simulate snowmelts or heavy
rainfall, as well as varying depths of soil
and degrees of thaws. The results of these
initial runs are now being compared to
field data collected during studies on the
Grand and Thames River basins during
1975 to 1978 by PLUARG (Pollution From
Land Use Activities Reference Group).
PLUARG was a major joint international
environmental study. It raised questions
in the erosion/sediment area that led to
Prof. Dickinson's study.
In a given area, erosion occurs in
pockets, depending on slope, crops, and
ADVICE ON FARMING
other factors, and, because conditions and
degree vary, remedies for specific prob-
lems will vary. It can be difficult to identify
the problem and choose an economic
course of action. To simplify the task,
Prof. Dickinson has developed a computer
modelling approach that analyses a
problem area, suggests specific remedies,
then evaluates their effect. For example, a
field near London growing "continuous
corn" has developed gullies, making
normal tillage practices impossible. After
analysing the data, the computer suggests
contour plowing and conservation tillage
(leaving refuse on the soil surface during
spring). Crop rotation with forage, such as
hay, is an alternative that would improve
soil structure, but a London area farmer
may not have livestock markets for his
forage.
With continuous cropping, the constant
plowing and exposure of the soil to air
breaks down soil structure, internal
drainage is reduced and top soil is lost.
Soil becomes "tighter and tighter" and
resists the plow. Planting a variety of
crops sustains productivity, reduces ener-
gy requirements for fuel and fertilizer and
reduces erosion. Prof. Dickinson says that
grandfather "used a package of reasons
that made good sense," and that the
present generation is just now realizing
the wisdom of those ways.
Remedial measures predicted by the
computer model have been implemented
for a year in two basins in the Thames
River area. Resulting field data will be
used to validate and adjust the model.
Then, if descriptions from the simulator
laboratory studies show that spring and
summer soils are indeed behaving differ-
ently, these results will be incorporated
into the computer model, explains Prof.
Dickinson. Conclusions will be possible by
the end of the two-year contract period.
The simulator, built for under 510,000,
will have further applications at the end of
this contract. What, for example, is the
effectiveness of using mulch to protect
roadside banks during seeding? The
computer model will be useful for looking
at erosion caused by urban development.
Consulting services in the application of
the model are already a marketable item.
Researchers do not know if erosion in
Ontario has reached a crisis situation,
explains Prof. Dickinson. They know that
there is little more than a plow's depth of
topsoil and that much is already gone from
hilltops and hillsides. A thousand acres of
topsoil moves downstream to the Great
Lakes each year, clogging ditches and
reservoirs. The agricultural chemicals
carried by this soil are major contributors
to the pollution of the lakes. Information
gained from Prof. Dickinson's study will
be used to control the movement of spring
soil, and our lakes as well as our farmland
will benefit.
Guelph University News Bulletin
We goofed
The Rural Voice apologizes for any
inconvenience caused by a story we ran on
page 31 of our December issue.
The story outlined the subjects, dates
and registration information for short
courses offered at Centralia College of
Agricultural Technology.
The information, however, was taken
from the 1981 brochure. The lineup was
impressive but it was also outdated.
A complete and correct program lineup
for 1982 appears in this issue of the Voice.
Again, we're sorry for the mistake. It
was ours.
MAILBOX OF THE MONTH
This month's
mailbox belongs
Hullett Twp.,
Huron County
r;
THE RURAL VOICE/JANUARY 1982 PG. 17