BLUE METAL CRUSHER DUST -
Agencies Information Services
metal crusher dust is left over at quarries when they are crushing
blue metal (volcanic basalt) rock to be used on bitumen roads.
The road constructors buy all of the suitably sized gravel. The
'dust', which contains about 80% dust and 20% fine grit up to
4mm in size, is sold for use in gardens, landscaping, lawns, drive-ways
and house slab foundations.
Australia has done a number of substantial trials on the
use of blue metal crusher dust for olive tree growth and health.
All trials have resulted very positively in favour of adding
blue metal crusher dust to the orchard site prior to planting.
Contains excellent minerals which are not water soluble and therefore
are not leached out and wasted, but are naturally available
to the tree roots as required.
Assists in the opening up and aerating of the soil for increased
and easier root growth and therefore increased foliage growth.
Increases rate of tree growth leading to heavier crops on the
Deep ripping the dust into the ground prior to planting
ensures that it is distributed through the areas where the
roots will use it in years to come. (Adding the crusher dust to
the ground surface of planted orchards may assist tree growth,
but is not nearly as effective as deep ripping it in prior to
We understand that crusher dust will also reduce the waterlogging
ability of the soil. This is not yet proven but some growers believe
this to be so. Extra drainage is important in an olive orchard.
The high pH of crusher dust (Approx. 9.0) helps to raise the pH
of the soil. As olives grow best in soil with a pH of between
7.0 and 8.0 this is also helpful.
It is much less expensive than other rock based mineral
supplements on the market. In fact, some products consist
of 50% to 90% blue metal crusher dust and yet they cost up to
15 times as much!
of Use - Prior to deep ripping, spread half to one builder's
wheelbarrow full of blue metal rock crusher dust at each tree
site. (One level barrow per tree = 12 trees per cubic metre.
One half barrow = 24 trees). Spread this over a 3m X 3m (10ft
x 10ft) area. This will then be deep ripped into the soil
along with the rotted manure and lime if necessary. For further
steps in land preparation see OLIFAX - 3.
Analysed by Incitec Ltd, PO Box 140, Morningside QLD, 4170.
9.1 / Magnesium mg/L 59.0
dS/m 0.12 / Sodium mg/L 22.0
mg/L 2.0 / Calcium/Magnesium Ratio 2.9
Nitrogen mg/L 11.0 / Potassium/Magnesium Ratio 0.20
Nitrogen mg/L 1.0 / Iron mg/L 14.0
Nitrogen mg/L 12.0 / Copper mg/L 0.44
mg/L 3.0 / Manganese mg/L 6.0
mg/L 0.0 / Zinc mg/L 0.0
mg/L 12.0 / Boron mg/L 0.04
mg/L 172.0 / Aluminium mg/L 1.0
Weight - Approximately 1.5 tonnes/cubic metre.
a Mulch - An excerpt on mulching from "The Land"
newspaper (12/10/95) gives another interesting perspective on
crusher dust. It reads as follows,
know a garden that was mulched 12 years ago with blue metal dust
left over from some road bitumen (no-one believes this story)
and hasn't been watered since. This garden had subsoil moisture
even in the middle of the 1980's drought, and everything
has grown vigorously."
water holding occurs when the crusher dust is used as a thick
mulch layer on the surface. (We have not seen trials where blue
metal is used as a mulch in commercial olive orchards). If the
crusher dust is deep ripped into the soil it helps to aerate the
soil, thereby allowing easier root movement and greater foliage
growth. No studies are currently available on the effects of deep
ripped crusher dust on the soil's water holding ability.
- Look up "Quarries" in your local Yellow Pages.
If they cannot help you, then the Main Roads Department or
local council should be able to give you the name of a Quarry
to contact. Remember, the only dust we are referring to in this
olifax is Volcanic Basalt dust - not any old rock dust that
may be superfluous to the quarries needs.