Subject: soil testing

From: [email-masked] ("Robert F. Enenkel")
Date: 4 Jul 93 23:57:11 GMT

I have some questions about soil testing.  I'm rather a neophyte at this,
so if there are any professional pedologists out there, I hope they will
bear with me.

Because of my involvement with
fish culture, I am used to testing for the concentrations of various ions
in water. For instance, I have tests for ammonia, nitrite, nitrate, phosphate, 
pH, buffering capacity, and hardness.  These tests seem like they should also
have relevance to measurement of soil fertility.  The first 5 seem directly
applicable, buffering capacity sounds like something I've heard called
lime requirement, and hardness might serve as a measurement of calcium and
magnesium.  But I have a problem.  I understand what it means to say that a 
sample of water has a certain pH, say, but what does it mean in relation to 
soil?

Presumably it means the pH of the soil solution...or does it?  What if there
is some acidic or basic solid in the soil.  Then might the pH not depend on
how much is rains, as more of the solid would then dissolve?  Even if this
situation does not occur (does it, usually?), you can't directly measure the 
pH of the soil solution directly, so what it seems you do is make an extract 
from the soil using distilled water, and measure that.  But then it depends 
on how much soil and how much distilled water you use, doesn't it?  

What I thought I'd do (before I realised how surprisingly complicated this all
is), is test my soil and compare the results to published values which are
optimal for various plants, and then try to influence these values to make my
plants grow better.   However, such values as I've found seem to be given in 
lbs/acre. Now, if a soil sample contains x ppm of some nutrient (that is, some 
mass of nutrient per volume of soil), how can I convert that to lbs/acre, 
which is mass per area, whatever that means?

Awaiting some (any) enlightenment...

Robert Enenkel

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From: [email-masked] (Gerry Thome)
Date: Wed, 7 Jul 1993 23:30:09 GMT

>Awaiting some (any) enlightenment...
Well, I don't know if I can enlighten, but I can comment.  Every year on our
farm we had every field tested for all sorts of things.  ph, nitrogen,
potassium, etc...  Depending upon the needs of the crop to be grown in
each field we added the proper minerals to each field.  I guess this
is what you're getting at.

Our county agricultural agent played a big role for us here, as he helped
take samples and got the samples analyzed.  You may want to contact your
local ag agency to see if any services are offered.

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From: [email-masked] (Rick Jenks)
Date: Tue, 13 Jul 1993 02:25:56 GMT

>which is mass per area, whatever that means?
                  
Robert,  I would suspect that the lbs/acre values tht you have read are 
consumption.  In other words Alfalfa consumes 40 lbs/acre of sulfur each
year (my fuzzy recollection, but don't hold me to it..).  So, you need to
maintain that amount in the soil.