The Rural Voice, 1979-07, Page 4Windbreaks,
woodlots and
shelter belts
More farmers are planting them and here's why
BY ALICE GIBB
Windbreaks, woodlots and shelter belts were once a common
sight on southwestern Ontario farms, but with today's larger
acreages under production, trees and even fences, have in many
cases, gone the way of the team of horses.
The result may be bigger fields, but the price farmers pay is
often the loss of valuable topsoil and blowing and drifting snow
in the winter months. With soil erosion becoming a serious
problem in southwestern Ontario, it isn't suprising that many
rural residents are returning to the practice of planting shelter
belts and erecting windbreaks.
As OMAF publications point out, wind erosion is a particular
problem where the land is flat, where fields are overcultivated
leaving a fine, smooth surface or where large areas of cultivated
soil exist without sufficient windbreaks or residue cover is
minimal. The result of wind erosion is lower soil productivity,
ditches and fencerows filled with valuable topsoil and poorer
crop yields.
One man who has been a proponent of windbreaks and shelter
belts for some time is Professor Frank Theakston of the School of
Engineering at the University of Guelph. Working with a
laboratory model called a "snow stimulator", an open channel
water flume where water represents the wind and silica sand
represents snow, Prof. Theakston and fellow researchers have
been able to study the effects of wind year round.
Prof. Theakston's research has convinced him windbreaks are
a valuable asset to any farmstead. Not only do they prevent soil
erosion, but they provide shelter for livestock, act as a barrier
against snow, and in a time of ever-increasing energy costs, help
conserve fuel. In short, while windbreaks add aesthetic value to
the farmstead, they also save the farmer money.
To understand the value of windbreaks, we first have to
mderstand something about a flow of wind. The ordinary
PG. 2 THE RURAL VOICENJULY,1979
streamline wind occurs over a flat terrain and continues in a
definitely controlled pattern of movement until the currents meet
an obstruction and then turbulence is created at the point of
disruption. It's important to realize there's always more heat loss
from buildings where turbulence or eddy currents are created
than in areas of pure air infiltration.
Shelter belts and windbreaks both have a decided effect on
reducing wind velocity pressures and in reducing heat losses
from farm buildings.
The first rule of thumb in erecting windbreaks is to position
them so they're opposing the wind force. The secret in doing this
is to find out what direction the prevailing winds are blowing on
your own farm - northwest or west winds are the most common -
and take this into consideration when erecting a windbreak.
For someone considering a permanent windbreak, trees are
the obvious solution. Frank Theakston recommends planting
coniferous trees in a double row, close planted about four feet
apart, located so they're in a position opposing the wind force.
The trees won't reach full effectiveness as a windbreak until
they're about ten feet in height.
Conifers are recommended since deciduous trees lose their
foliage in the fall, thereby not providing any shelter in the winter
when it's needed most. Also. deciduous tr.'-s add to the
"Venturi" effect when the wind velocity is increased when it
passes through a narrow gap.
Poplar trees, often a popular choice for windbreaks since they
grow so quickly, rank about the lowest on Professor Theakston's
list of species to plant. Poplars, he warns, just aren't an effective
wind control device.
Trees aren't the only natural form of windbreak - shrubs can
also be planted along laneways or fields to prevent wind damage.
Frank Theakston recommends planting Chinese elm, which
reaches up to six feet in height, or other shrubs which are very