permaculture

[sinergyinaction@netscape.net]

Hi Kevin
well this is one more demonstration that it is not always easy to work with 
nature.
Many thanks for this explanation, I have learned quite a bit from all answers
All the best
Antonio
 
 
-----Original Message-----
From: ktopek@houston.rr.com
To: permaculture@lists.ibiblio.org
Cc: mvanderford@houston.rr.com
Sent: Fri, 17 Nov 2006 2:55 AM
Subject: Re: [permaculture] Gypsum does not increase pH!


All, especially Antonio, Jerome and Toby,

Regarding gypsum use on clay, this is my experience. After adding gypsum to
a Beaumont Clay soil, starting pH of 6.5, the pH increased to around 8.0
within a month.  The clay is highly weathered, semi-tropical, compact and is
submerged several times a year (~ 60 inches rain/yr)

Attached are a couple of interesting documents.  Please refer to the calcium
speciation diagram.

The exact reason for the increase in pH is difficult to determine. The
proposed scenario is as such:
Gypsum is dissolved by acidic soil water containing carbonate species.
Carbonate species are supplied by active soil bacteria oxidizing organic
matter, which is ongoing in warm semi-tropical soils.  Calcium speciation
shifts to calcium carbonate (see speciation diagram).

Anaerobic sulfur reducing bacteria in the clay interstices utilized the
available sulfur as a terminal electron acceptor. The reduced sulfide either
combines with iron, is volatilized or contributes to soil toxicity. The
sulfate is removed from the soil and does not contribute to acidity. The
calcium increases alkalinity in the soil.

The result was vegetables would not
grow at all in this site for a year after adding gypsum. Only heavy mulching
with compost improved the soil's growing capacity years later.

I should have specified my soil type and rainfall pattern,
since these conditions vary around the globe and are critical to soil
chemistry . I apologize for any misleading statements
I may have given.

Kevin Topek, including lots of thought and discussion with my wife, Mindy
Vanderford


----- Original Message -----
From: "Toby Hemenway" <toby@patternliteracy.com>
To: "permaculture list" <permaculture@lists.ibiblio.org>
Sent: Wednesday, November 15, 2006 8:20 PM
Subject: Re: [permaculture] Gypsum does not increase pH!


> In general most of the problems that gypsum is recommended for, like
> buffering pH problems and breaking up heavy clay, can be solved by adding
> organic matter, and perhaps rock dust as well. But gypsum is faster at
> solving some problems if you have really bad soil.
>
> I had very good success with gypsum when I found that the large organic
> garden at my previous rural home had soil pH of 8.2 due to the previous
> owner's dumping of 4 cords worth of wood ash per year on a 5000-square
foot
> plot. Most nutrients are locked up at the pH, and there's no way I could
get
> enough mulch to buffer the pH. I added about 300 lbs of gypsum over the
> course of 4 months, and found that the pH had dropped to 7.0. Gypsum will
> acidify soil that is alkaline, because it dissolves in water to yield a
> dilute acid: the CaSO4 dissociates to H2SO4 or sulfuric acid, in small
> quantities. If soil is acid, it doesn't seem to make it more acid, though,
> something I don't really understand. So contrary to what Kevin said, it
> cannot increase pH, but it can lower it.
>
> The calcium in gypsum also replaces troublesome positively charged ions
> (cations) such as aluminum and sodium. It's good for salted soils.
>
> Gypsum did a great job of loosening up the heavy clay of my garden, too,
> although over the next few years I added about 2 feet of mulch, which
> improved the soil at least as much as the gypsum. One side effect is that,
> because it contains sulfur, onions and garlic grown with gypsum will taste
> very strong. Alliums get their intensity from a sulfur-containing
compound.
>
> I know that gypsum is eschewed by some organic purists because it is a
> chemical and it alters soil structure. But in the right circumstances, it
> can fix some serious soil problems. There's a very "rah-rah" article at
> http://westernfarmpress.com/mag/farming_essential_amendment_high/
>
> And here's a quote from
> http://www.abc.net.au/gardening/stories/s131432.htm
> on how to know how much gypsum to add and when soil can benefit from it:
>
> "However, not all clays respond well to gypsum. To find out which ones do,
a
> simple test known as the Emerson Dispersion Test can be done.
>
> EMERSON DISPERSION TEST: Drop a piece of dry soil aggregate, about 6mm
> across, into a glass of rainwater. Don't move the glass - just watch what
> happens to it after an hour and then after 24 hours. If it slowly
disperses
> into the water, first forming a halo of clay particles around the
aggregate,
> it will respond to the addition of gypsum to the soil. If it does nothing
at
> all in the water, it would be a waste of time adding gypsum to the soil as
> it won't respond. The greater the cloudiness of the water and the more
> rapidly it develops, the greater will be the benefit of adding gypsum to
the
> soil and the higher the amount needed.
>
> If you have soils which respond to the Emerson dispersion test, add gypsum
> at a rate of 0.5 - 1kg per square metre, digging it in well. Read the
label
> and stick to the recommended amount. Too much gypsum will spoil the soil
> structure and a slurry may result.
>
> It's a good idea to add lots of organic matter as a mulch after digging in
> the gypsum, or to grow and dig in a green manure crop."
>
> Toby
> http://patternliteracy.com
>
>
>
>
> _______________________________________________
> permaculture mailing list
> permaculture@lists.ibiblio.org
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