[Arid_gardener] Granite as soil amendment

[Chris Trask]

     I used gypsum for years to try overcoming the problems of clayish soil, and the results were poor at best.  However, when I worked at the Boyce Thompson Arboretum I quickly learned that the far better long-term solution is to remove the clay by excavating to a depth of a foot or more, and then backfilling with a 1:1:1 mixture of soil, compost/mulch, and coarse sand (1/8 inch sift and smaller).  I applied this method to my own garden, and there has been a tremendous improvement in the establishment of new plantings, seedling emergence, and overall plant health.  

     You can buy the 1:1:1 mixture from any number of landscaping suppliers, and you may want to do a simple soil test of your own to ensure that the clay content is at a suitable level.  For a 1-gallon planting, you should excavate a volume equivalent to a 5-gallon paint bucket, and after a while the spaces between the plants can be excavated and backfilled as well, which improves the drainage and reduces the occurance of root rot.


-----Original Message-----
>From: Bill Woody <billw-9 at msn.com>
>Sent: Oct 3, 2006 2:45 PM
>To: arid_gardener at CALS.arizona.edu
>Subject: [Arid_gardener] Granite as soil amendment
>
>Most of the rock and gravel companies sell 1/4-inch washed granite,
>essentially no fines.  Also, most of them have displays where you can see
>what it looks like.
>
>This is meddling rather than answering your question.  I tend to think that
>bark or mulch would be better than granite to loosen clays if you want to
>grow things in the amended soil.  They are also much easier to transport and
>handle, unless you're a muscular young guy with your own truck.  I'm
>assuming you have a small plot, not a half-acre.
>
>More authoritative responses from the MGs are welcomed.
>
>Bill Woody
>
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Chris Trask
Outings Leader, Sierra Club (1981-1991)
Palo Verde Group Outings Chair, Sierra Club (1985-1988)
Grand Canyon Chapter Outings Chair, Sierra Club (1988-1991)
Member, Arizona Native Plant Society
Member, Arizona Governor's Advisory Council on Invasive Species
Member, Central Arizona Weed Management Area