On Wed, 18 Dec 2002 14:24:52 +1100, "Judanne"
wrote:

His theory is that the most fertile lands on Earth have this rock dust in
the naturally because of glaciations. This apparently didn't happen in
Australia and so he adds his own. He reckons that since using this, which
he says is not a fertilizer, but rather a mineral supplement for the soil,
his fruit has been tastier.

Your friend has the right results, but his theory is a little off.
Many parts of Australia have undergone glaciation in the past (at one
time it was very close to the South Pole), but most of it isn't
visible today due to weathering. The real reason that Australian soils
are generally depleted is because they are comparatively old, and have
been in a comparatively tropical climate, getting a lot of rainfall
(in the past) that leaches the nutrients from the soil.

Your friend was right about the mineral supplements. Everything,
plants and animals, need trace minerals to thrive and that is missing
from our fertlisers. A good example of trace element uptake is
selenium in Brazil nuts. Apaprently Brazil nuts from the Amazon region
are very high in selenium, whereas Brazil nuts from most other regions
in the world don't contain it. Consequently Brazilian brazil nuts (and
now this just sounds silly) get a premium price.

Rock dust is a great way to replace trace elements in the soil. What
trace elements your plants get will depend very much on what's in the
dust that you use, but I have read several studies on it, none of
which hae yet discovered any adverse effects.

He's given me about a litre of the rock dust to use on my plants.

Go right ahead and use it. From my research it could do a lot of good.
At the least it isn't going to do any harm.

Tara