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 20:39:14 -0500
From: Elaine Ingham <soilfoodweb@AOL.COM>
To: SANET-MG@LISTS.IFAS.UFL.EDU

Hi Lawrence -

The assumption that you are making is that if nutrients are in solution,
then those nutrients WILL BE taken up by the plant.

That is not a valid assumption.

I can show you data where the soil chemistry test showed LOTS of soluble
phosphate (or nitrogen, or calcium, or iron or whatever) in soil 
solution, but assessment of the PLANT tissue showed practically no 
phosphorus (or nitrogen, or calcium, or iron or whatever).  And yes, the 
plant was dying.

Just because the "plant available" test, or soluble nutrient test, or
exchangeable nutrient test, shows high levels does not in any way 
predict whether the plants will in fact, take that soluble nutrient into 
the plant.

I can show you soils with EXTREMELY low phosphorus concentrations (0.1
ppm for example and yes, the agronomist was going crazy,
practically screaming at me to pour on the phosphate fertilizer), but
the plants exhibited no nutrient limitation at all, with plenty of
phosphate in the plant tissue.  The plants never showed ANY nutrient
limitation, even though the soil chemistry tests showed "severe 
depletion" of soluble nutrients.

Go to a mature pasture, or an old growth forest.  The growth demand of
the plants on soil nutrients must be massive, right?  But there are no
signs of plant stress or poor fertility in those soils.  Do a soil 
chemistry test.  Very low nutrient concentrations all the time.  Ah, but
those nutrient levels are constantly maintained.

You don't need 450 ppm phosphorus in the soil to grow a plant. In fact,
to make certain nutrient leaching will not occur, you probably
don't want more than - well, what's a good number here? -- 1 or 2 ppm
phosphate in soil solution at any instant in time.  Given the forest 
example, maintaining low but constantly replenished nutrients
levels is what is desirable.   I'd like to see funding go to
establishing what those low nutrient levels should be for different
plants, given adequate biology to cycle nutrients all the time and 
maintain those constantly replenished levels of nutrients.

So, you might ask why we rely so much on soil chemistry tests, since
they may be so mis-leading.

Just think about who is tying to convince you to do...... what..... when
that soil chemistry test comes in showing low soluble nutrients.

Is your only choice to run out and pour chemicals on?  Hasn't the
organic world shown that is not the way to deal with this?

You put compost on, but what is it about compost that will fix the
problem?  Hum......... it is the biology in that compost that is the
real secret........

Elaine R. Ingham
President, Soil Foodweb Inc.