[Arid_gardener] Question from Home-Hort WWW page

[Olin Miller]

----- Original Message ----- From: <edjeter at cox.net>
To: <arid_gardener at Ag.arizona.edu>
> I read an article recently recommending using quarter-10 gravel (washed)
> to amend clay soil and improve drainage.  This gravel contains pieces 1/4"
> to 1/10" in diameter and is washed to remove the fines.  The article also
> recommended using this to mulch certain plants such as lavender, etc.  I
> have been unable to find this product in the valley and was wondering what
> you would recommend I use as a substitute.

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Dick makes a good point as to being more precise regarding the definitions
of amendments and mulch.  Many of us, including me, often (erroneously) use
the terms interchangeably when we work last season's organic mulch into this
season's garden soil.

Although the following doesn't answer the question directly as to where he
can buy the 1/4-10 product, I would not try to alter the texture of the soil
by adding inorganic material.  Instead, I would amend the soil with compost
and also add a fast-acting soil sulfur, like Dispersul, then follow up later
with the slower-acting, pelleted soil sulfur.  I would also top-dress with a
layer of organic mulch; I also frequently use compost for that.  Shredded
newsprint can also be used as a mulch if compost is not readily available.

I beliieve the current recommendation by the U of A is that gypsum in the
form of Calcium Sulfate only displaces Sodium in salty soils.  My experience
is that it also improves tilth and drainage but using it for that is
currently not an official recommendation.

Olin Miller
Master Gardener Volunteer, Maricopa County AZ
http://home.att.net/~millero/ValleyOfTheSunGardeners.htm

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----- Original Message ----- 
From: "Bill Woody" <billw-9 at msn.com>
To: <arid_gardener at CALS.arizona.edu>
Sent: Tuesday, October 03, 2006 2:45 PM
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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----- Original Message ----- 
From: "Chris Trask" <christrask at earthlink.net>
To: <arid_gardener at CALS.arizona.edu>
Sent: Wednesday, October 04, 2006 8:25 AM
Subject: Re: [Arid_gardener] Granite as soil amendment


>     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.

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----- Original Message ----- 
From: "Dick Gross" <rkgross3 at cox.net>
To: "Chris Trask" <christrask at earthlink.net>;
<arid_gardener at CALS.arizona.edu>
Sent: Thursday, October 05, 2006 8:25 AM
Subject: Re: [Arid_gardener] Granite as soil amendment


Someone will correct me if I am wrong but I think we are confusing terms. A
"soil mix" or just the tern "soil" is a mixture of any materials or "media"
in which a plant's roots take residence to extract water and nutrients to
build new cells and the hardware to reproduce itself, roughly speaking,

A mulch, on the other hand, is any material--newspapers, plastic, rock, wood
chips, any other debris placed on top of the ground, not in, or not as an
integrated part of the media in which the roots reside. Organic material
mixed into the soil continues to decompose consuming, as it does, nitrogen
needed for plant growth. If one is aware of this contrived deficiency,
additional nitrogen can be applied to make up the difference. But the
condition is suttle and we may mot properly diagnose the problem.

We might mix crushed rock or sand in ground to improve tilth, drainage or
aeration but we call it a soil ammendment, not mulch. Mulch is placed on top
of the root media for esthetic purposes or to conserve moisture by
decreasing evaporation. There is an interaction at the interface between
organic mulch and the soil organisms that is beneficial but those organic
compounds will have been well decomposed by the time they have gone through
the guts of the organisms in the soil.

Whatever one does to soil, it is essential that irrigation water percolate
through and out of the root zone flushing salt out and pulling air in behind
it. Roots cannot survive without air and we all know the deleterious effects
of salt.

This analysis may not be technically correct in every aspect but if anyone
is uncomfortable with the explanation, we might all benefit from the
additional dialogue.

Dick Gross, Master Gardener Volunteer
University of Arizona
Maricopa County Cooperative Extension

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