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Mechanical Land Clearing I
Us'e of the Bulldozer
The belief that the buljdozer
could revolutionise the clearing of
light or medium timbered land in
this part of the country has been
fully borne out as the results of
trial on several properties during
the past few months. In the latest
issue of the "Journal of Agricul
ture," Mr M. Cullity (Superintend
ent of Dairying) and Mr C. W.
Tobin (Dairy Instructor) supply
the particulars in an interesting
article. We published articles on
the work of the machine at the
time it was operating, and the final
summing up by these experts add
to the information and views then
expressed.
It is explained that during 1044
a D7 bulldozer, caterpillar type,
owned and operated by the PWD,
was made available for clearing
land intended for potato growing
in the South-Western districts. A
programme of demonstrations cov
ering many different types of
country in the area was planned.
A commencement was made near
Kendenup in January last and since
then several other parts were vis
ited. It is intended that following
the demonstrations in the South
Coastal districts the machine will
be made available for sinking
dams in certain key districts, and
will then be moved to the lower
South-Western area for the car
rying out of further clearing de
monstrations. The cost of operat
ing the machine is estimated at
£10 per day of eight hours.
The following reports give some
idea of the type of work perform
ed and the interest which has been
displayed by farmers:
\V. Frost, Kendenup.-The first
demonstration was commenced on
Mr Frost's property. Timber here
represented a fair average of that
in Mt Barker-Kendenup district,
being jarrah, red gum, yate and
small white gum; soil of light
gravelly to dark sandy type, unaer
which is a clay pan. The area
cleared was 135 acres on two
blocks, one 111 acres and the other
24 acres; timber density averaged
150 to 200 trees to the acre, from
4in to 15in in diameter, also a few
large dry trees standing and all
except four were removed. Far
mers showed a keen interest in
examining the holes left after the
trees were pushed out, how many
trees were broken off at the bot
tom, etc. The result was particu
larly good; root holes were not
deep, because the bulldozer blade
swept over the ground in pushing
the tree away from the hole, and
therefore- the soil was practically
all replaced. Breaking off amount
ed to only 5 per cent, while trees
left standing averaged only five to
the acre.
_A. Bracknell, Napier.-Twenty
miles north-east of Albany; Lands
Department settlement block about
14 years old; 22 acres virgin jar
rah-red gum country in one block
and 4-L acres in another were
cleared in four working days.
Timber density 100 to 150 trees to
the acre, Gin to 3Gin in diameter;
light gravelly type of soil with
clay about 2ft below the surface.
The large trees on the virgin
country were not as firmly in the
ground as re-growth timber dealt
with earlier, and the machine could
push out some trees up to 2ft Gin
in diameter. On the first block
nine trees to the acre (five red
gum and four jarrah) over 2ft in
diameter, were left standing. On
the second block six to the acre
(four red gum and two jarrah).
I C. T. Horfin, Kronkup.-On this
property various classes of clear
ing were undertaken, and in all
8G acres were cleared in 124 hours.
To obtain a reasonable estimate of
costs the area has been sub-divided
into five parts and comments made
on each separately. (1) Twenty
acres of 25-year-old re-growth
karri and red gum saplings from
Gin to 12in in diameter growing
on deep red sandy loam soil. Dens
ity. 400 trees per acre. The trees
were tall, strong and firmly root
ed, and the timber density made
heavy going for the machine, es
pecially after timber had been
knocked down. The percentage of
broken off trees was higher than
anything else dealt with down
here, and this is probably due to
the accumulation of down timber
congesting the area being cleared.
The karri was particularly difficult
to root out. Twenty trees to the
acre were left standing, and ap
proximately 20 per cent broken off
at the bottom. Working time, 37
hours. (2) Twenty-two acres red
gum and karri saplings up to 12in
in diameter, and blackboys. Sap
lings GO to the acre and blackboys
about 250. One tree to the acre
left, and 10 per cent broken off.
All blackboys cleared right out.
Working time, 32 hours. (3)
Eighteen acres of blackboys in
cluding five to six dry trees to the
acre 1ft to 2ft in diameter. Black
boys 400-500 to the acre. Dark red
sandy soil. All trees were knock
ed down and blackboys were swept
into windrows. Less than one per
cent blackboys broken off. Working
time, 18 hours. (4) Seven acres
half red gum and karri saplings
similar to No 2 area, and half
blackboys similar to No 3. Four
trees to the acre left and all black
boys cleared out. Working time.
II hours, (5) Nineteen acres of
dry red gum and jarrah trees 1ft
to 3ft in diameter, 150 to the acre.
Trees were knocked down and
swept into large heaps ready for
burning. Only five trees left
standing on the whole area. Work
ing time, 2G hours. This is parti
cularly interesting because a pad
dock of dry timber had not pre
viously been undertaken down here,
and it is now evident that the ma
chine can deal with this type of
clearing just successfully as any
other jobs so far tackled. The li)
acres can become a totally cleared
paddock under pasture in six
months if the fire is put in early.
The demonstration was witnessed
by at least seven to eight hundred
visitors.
W. H. Young, Young's Siding.
When the bulldozer was put to
work on this blackboy flat on
March 15 it was soon evident that
this type of country presented no
difficulty whatever to the D7 mach
ine. 'In eight working hours, eight
acres of blackboys were knocked
out and swept into rows. Several
places had 800-900 blackboys to
the acre and the whole area would
average approximately 550. The
number per acre made practically
no difference to the running of the
machine, 900 being knocked down
as easily as 400; breaking off
amounted to only two per cent.
The lesson learnt from this dem
onstration is that the D7 machine
is only working on about one-third
of its power when clearing this
type of country with a 12ft blade.
The pre-war price for knocking
down blackboys, using a horse, was
£5 per acre. We might add that
the blackboys had then to foq
stacked, whereas with the bulldozer
they are neatly packed in wind
rows ready for the burn.
Conclusion.-The demonstrations
proved successful in every respect
and have provided proof of thg
possibility of reducing costs of de
velopment in the types of country
in which the machine was used.
The large volume of applications
by farmers for the use of the bull
dozer has indicated their confid
ence in this method of clearing.
Apart from a considerable reduc
tion in cost, an impressive feature
is the speed with which the work
is completed.
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