permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

-------- Original Message --------
Subject: Re: [SANET-MG] Question for Elaine: Fwd: Re: [permaculture]
Fwd: Re: [SANET-MG] Soil minerals and nutrition
Date:   Tue, 28 Dec 2010 19:48:37 -0500 (EST)
From:   soilfoodweb@aol.com
To:     SANET-MG@LISTS.IFAS.UFL.EDU, venaurafarm@BELLSOUTH.NET

Standard soil chemistry reports do not report total nutrients in the
soil routinely. Rather, the information is soluble, or what is called
plant available. There is no guarantee that a plant will take up what is
in the soluble pool, and in fact, there are papers in the scientific
literature that show what is in the soluble pool has no bearing on what
the plant actually takes up.

The fairly standard "Base Saturation" information given on many soil
reports is not a total nutrient test either, but only an assessment of
nutrients that are surface bound and in solution. The nutrients assessed
by the soluble test I spoke of above is including in the base saturation
value. I like to think of the base saturation information as the
nutrients that are more or less loosely bound on the surfaces of sand,
silt, clay, and on the surfaces of organic matter. But this does not
include the nutrients in the organisms, inside the organic matter
clumps, does not even begin to tell you about what is held inside
pebbles, rocks and stones, or in any part of the soil that water is not
currently moving into.

Total nutrients require the soil to be ground to small particle size (1
to 5 micrometers for example), solubilized with extremely strong acid
(reagent grade sulfuric, or nitric or hydrochloric acid for example),
and once completely solubilized, the liquid is assessed for nutrient
content using AA, or Mass Spec for example.

Again, most labs do not do total nutrient assessment on soil. they may
do this procedure on plant material, but not routinely on soil. If you
ask a typical soils lab if they can do total nutrients on soils, you
will often be told they cannot. I have been told they cannot, for
example, until I point out to them that a total nutrient analysis for
soil is what they do for plant total nutrients.

As with all these assessments, the exact extracting agents used, and the
sequence used, make big differences in how much is actually extracted.
I've worked with some chemists where they used 1 or 0.1 gram of soil as
their sample, and after extraction for "total nutrients" there was black
"gunk" left at the bottom of the extracting container. I asked if
leaving that material made a difference, and they said "Insignificant".
But then when we tried to account for the nutrient budget in those
soils, the results didn't make sense. It turned out that significant
amounts of most of the nutrients actually was left behind in that
"little bit of gunk".

So when someone says that "the soil has lost all its nutrients", they
can ONLY be referring to soluble, and possibly, maybe exchangeable,
nutrients.

Until such time as your soil runs out of sand, silt, clay and/or organic
matter, it is not possible for your SOIL to be lacking in nutrients. At
least that's what I am seeing, based on working with soil chemists in
lots of different places.


Elaine R. Ingham
President, Soil Foodweb Inc.