[Market-farming] Market-farming Digest, Vol 93, Issue 18

Michael Astera michael.astera at gmail.com
Sat Oct 16 15:54:23 EDT 2010


Hi all, long time reader, first time poster.

To answer the question about whether gypsum is better for adjusting the
Calcium/Magnesium balance in the soil, it depends.

Gypsum averages 22%Ca and 16%Sulfur.  If the soil needs Sulfur (e.g. has
less than 50ppm S on a soil test) then gypsum is a good choice.  If the soil
is above pH 7 gypsum is also a good choice, as the S will tend to lower the
pH a little.  Gypsum is also fast-acting and more soluble than regular ag
lime.

Even if the soil is pretty acid, below pH 6, gypsum can still be a good
choice if Sulfur is low.  Usually I recommend adding enough gypsum to bring
the Sulfur up to optimum, then fill in the rest of the needed Calcium with
high-Calcium lime or even Calcium hydroxide, mason's lime.

You won't find much in the ag literature about Calcium loosening soils and
Magnesium tightening them, but it is the truth.  The research on it wasn't
done by the ag industry though, but by the people who drill oil wells.  They
use clay as a lubricant in the borehole and need to modify the Ca/Mg ratio
to get the right consistency. The general rule for ag soils is based on the
cation exchange capacity of your soil, the CEC, which should be listed on
the laboratory soil report.  Basic rule of thumb is 65% Calcium to 15%
Magnesium. A heavy clay soil will do better with 70-80% Ca and 10%Mg, a
loose sandy soil needs more like 20%Mg and 60%Ca.

Here's a link to a basic explanation of how it works and how to calculate
it:
http://soilminerals.com/Cation_Exchange_Simplified.htm

Michael A
http://soilminerals.com

Date: Fri, 15 Oct 2010 14:03:40 -0400
From: "Mac" <gofish54 at centurytel.net>
To: "Market Farming" <market-farming at lists.ibiblio.org>
Subject: Re: [Market-farming] Garden covering
Message-ID: <20101015140340.bhaf0amenvkkw8cw at webmail2.centurytel.net>
Content-Type: text/plain;       charset=UTF-8;  format="flowed"

I am interested in making this change.  Our soil has a lot of Mg in it
and so does the ag lime that comes from local quarries.  Will using
gypsum instead of lime be the best way to accomplish this shift?

Thanks - mac

Quoting waldenfarm <waldenfarm at bellsouth.net>:
>
> Minerals- If you need to add calcium, use gypsum instead of lime. Also,
work
> towards shifting your Magnesium level to the low end of the Ca-Mg balance.
> Mg is "sticky" and adds to the "tightness of a clay soil.
>



On Sat, Oct 16, 2010 at 1:24 PM,
<market-farming-request at lists.ibiblio.org>wrote:

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> Message: 1
> Date: Fri, 15 Oct 2010 14:03:40 -0400
> From: "Mac" <gofish54 at centurytel.net>
> To: "Market Farming" <market-farming at lists.ibiblio.org>
> Subject: Re: [Market-farming] Garden covering
> Message-ID: <20101015140340.bhaf0amenvkkw8cw at webmail2.centurytel.net>
> Content-Type: text/plain;       charset=UTF-8;  format="flowed"
>
> I am interested in making this change.  Our soil has a lot of Mg in it
> and so does the ag lime that comes from local quarries.  Will using
> gypsum instead of lime be the best way to accomplish this shift?
>
> Thanks - mac
>
> Quoting waldenfarm <waldenfarm at bellsouth.net>:
> >
> > Minerals- If you need to add calcium, use gypsum instead of lime. Also,
> work
> > towards shifting your Magnesium level to the low end of the Ca-Mg
> balance.
> > Mg is "sticky" and adds to the "tightness of a clay soil.
> >
>
>
>
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> End of Market-farming Digest, Vol 93, Issue 18
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