Re: [tomato] blights

Olin (
Wed, 28 Apr 1999 17:44:11 -0700

Rock phosphate is so insoluble in alkaline soils that it is of little or no
value as a source of plant available  phosphorus.  I was assuming rock dust
to be a powder form of rock phosphate (not certain if that is so) and it
would also be insoluble.  It is probably great for acid soils.  There was a
thread on this topic 2-3 years ago on
the U of A arid_gardener listserv.  The final word is from the U of A soils
department archived at   As you suggest,
mineral depletion is not a normally problem in our desert soil with the
possible exception of iron and zinc (required by citrus) which are deficient
in some areas.  -Olin

-----Original Message-----
From: Thomas Giannou <>
Subject: Re: [tomato] blights

>... why would rock dust be inappropriate to desert soils?   ... Perhaps in
your soils mineral
>depletion by plants may not be a problem?   .../