OLIFAX - 10

- BLUE METAL CRUSHER DUST  -

Olive Agencies Information Services

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Blue 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.

Olives 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.

Advantages -

1. 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.

2. Assists in the opening up and aerating of the soil for increased and easier root growth and therefore  increased foliage growth.

3. Increases rate of tree growth leading to heavier crops on the increased foliage.

4. 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 planting).

5. 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.

6. 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.

7. 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!

Method 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.

Mineral Analysis - Analysed by Incitec Ltd, PO Box 140,  Morningside QLD, 4170.

pH 9.1 / Magnesium mg/L 59.0

Conductivity dS/m 0.12 / Sodium mg/L 22.0

Chloride mg/L 2.0 / Calcium/Magnesium Ratio 2.9

Nitrate Nitrogen mg/L 11.0 / Potassium/Magnesium Ratio 0.20

Ammonium Nitrogen mg/L 1.0 / Iron mg/L 14.0

Total Nitrogen mg/L 12.0 / Copper mg/L 0.44

Sulfur mg/L 3.0 / Manganese mg/L 6.0

Phosphorus mg/L 0.0 / Zinc mg/L 0.0

Potassium mg/L 12.0 / Boron mg/L 0.04

Calcium mg/L 172.0 / Aluminium mg/L 1.0

Dry Weight - Approximately 1.5 tonnes/cubic metre.

 

As a Mulch - An excerpt on mulching  from "The Land" newspaper (12/10/95) gives another interesting perspective on crusher dust. It reads as follows,

"I 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."

This 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.

Source - 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.