[NAFEX] Soil Testing 101

Jim Fruth jfruth at uslink.net
Fri Oct 20 10:32:44 EDT 2006


Mark,
    If Cation Exchange Capacity is too low a number, the soil tester would 
recommend adding organic matter.  Generally, anything higher than 3% is 
satisfactory.  If your Cation Exchange Capacity is too low, adding 
fertilizer would be a waste of time and money because much of it would leach 
away.  Organic matter molecules have positive and negative sites which act 
like tiny magnets.  Chemicals, fertilizers, have positive and negative too 
that (loosely) attach themselves to the organic matter's sites.  Soil should 
contain at least 3% organic matter to provide sufficient positive and 
negative sites to hold onto the amount of fertilizer needed to sustain 
healthy plant growth.   This bond between organic matter and fertilizer is a 
weak one and plants can strip the fertilizer molecules away from the organic 
matter.  This is a rather simplistic way of explaining Cation Exchange 
Capacity which leaves out the action of soil bacteria.
    Re your pH of 6.9, peaches do best within a pH range of 6.0 to 7.5.
    Your soil test results and fertilizer recommendations could be a bit 
more comprehensive and explanatory and etc. but, as you said, you were 
looking for cheap.  When I get my soil test results back from K Ag, Oshkosh, 
WI, they tell me how much of what fertilizer to apply whereas your lab told 
you how many pounds of what element to apply; you should have, at least, 
Chemistry 202 to be able to figure it out so you will have to hope that 
someone at your fertilizer store has an associate degree in Chemistry.  As 
for S (sulfur), perhaps 11 ppm is sufficient for peaches, but then, you'll 
be getting a slight boost when you apply zinc (sulfate).
    What about molybdenum?  Plants don't need much of it but, since this is 
your first soil test, I would have wanted a number for it.  An anecdote 
about molybdenum involves the settling of Australia: There were lush 
grasslands in an area of Western Australia that farmers flocked to but 
didn't stay long.  After their third planting season, the land stopped 
producing, prompting farmers to give up and move elsewhere.  Then, back in 
the 1930's molybdenum was discovered to play a vital role in plant 
development and this place (the name of it escapes me) was void of the 
element.  So they added some and the area became fertile once again.
    Yes, phosphorus does, generally, move slowly through the earth.  That's 
because everything that lives needs it.  The bacteria are going to grab it 
first and that gets into a subject that your lab didn't tell you:  If you 
spread the fertilizer, then go through with your rototiller to take the 
nutrients down into the root zone, you'll likely do damage to your trees. 
The idea is to spread it now, in late Fall, after the trees go dormant, and 
let the Winter snows (In your case, rains) take it down into the root zone 
come next Spring.  With phosphorus, we want a quantity in the soil so that 
there is some left over for the crops after the bacteria get their fill.  Of 
course, phosphorus, et. al. become available to plants when bacteria die. 
Worthy of mention is that phosphorus moves down to the root zone faster if 
you use a very soluble form of it, say, Mono-Ammonium Phosphate rather than 
some of the less expensive forms.
    Aaaaaaah, fertilizer mixing.  Most commercial mixers are too large to do 
a satisfactory job mixing the tiny quantity you need.  My orchard is only 
one acre big/small and my fertilizer dealer had a good belly laugh when I 
asked him to mix it.  Here's what I do:  Before I get into that, I'll back 
up recommends I spread 8-16-36, a soluble fertilizer that I don't have the 
equipment for and my fertilizer dealer only has 10-10-10 or 20-20-20 both of 
which have a higher nitrogen content than called for so I ask for basic 
fertilizers which, when mixed, give me the called-for quantity..  I have 
three distinctly different requirement areas, trees, bramble and acid ground 
, so I need three different mixtures.  I used to mix it by hand using pails 
and a hand trowel - now I use a 3 cubic foot cement mixer.
    Mark, you are fortunate.  When I teach a class, the students pay to 
attend.  You are getting it for free.  Oh, and regarding your last question, 
below, you hired the soils lab to do the job.  Follow their directions 
rather than collect hearsay from anyone who doesn't know what your soil 
needs.

Jim Fruth
Brambleberry Farm
Pequot Lakes, MN  56472
www.bberryfarm.com
(218)568-8483 [Store]
(218)831-7018 [My Cell]

I recently had my soil tested and had some questions about it.  I wonder if
some of you would be interested to look over the results below and offer any
comments.  I don't know diddly about agronomy.

The soil sample was taken from 10 holes.  In a post, Jerry recommended A&L
labs several months ago and it turned out they were the cheapest lab I could
find for the amount of testing done.  The lab had a very fast turn around
time.  Here are the results:
All numbers are in PPM unless otherwise noted.  Also, they rated the amount
of each element as either (Very Low-VL; Low-L; Medium-M; High-H; Very
High-VH)

Organic Matter=4.8%;  Phosphorus-Bray P1 ppm-P=5(VL);  K=101(M);  Mg=330(H);
Ca=2900(H);  S=11(M);  Zn=3.5(M);  Mn=33(H);  Fe=24(H);  Cu=1.7(H);
B=1.0(M);  Soil pH=6.9;  CEC-meq/100g=17.8;  Percent Base
Saturation-(%K=1.5; %Mg=15.5; %Ca=81.6; %H=1.5)

I also asked for fertilizer recommendations for peaches.  Here they
are(lbs/acre):

Lime=0;  N=65;  Phosphate-P205=100;  Potash-K20=95;  Mg=0;  S=0;  Zn=2.5;
Mn=0;  Fe=0;  Cu=0;  B=1

Here are some questions I have.  Any help would be appreciated, as well as
any comments.

-Zn, B, K, and S are all listed as Medium in amount, but the recommendations
only call for adding Zn, B, and K(Potash).  What about S?

-I thought peaches require a pH of 6.5.  I can't see that the fertilizer
recommendations would lower the pH.  Is 6.9 OK for peaches?

-What in the world is Cation Exchange Capacity (CEC)?  Is it very important?

-I only have about one acre of land and am growing fruit trees on about 1/2
of it.  Am I likely to find a Coop that will mix such a small amount of
fertilizer?  If so, any idea on what would be a fair price?  I would
probably need it bagged.  If they won't mix it for me should I just try to
buy some raw phosphate since it's most lacking in the soil?

-I've read P only moves down about 1 inch per year.  Will I likely have to
put it on every year?  Would it help to put a little extra on the first year
since it's so low?

Thanks,
Mark Angermayer
Zone 5 Kansas


I recently had my soil tested and had some questions about it.  I wonder if
some of you would be interested to look over the results below and offer any
comments.  I don't know diddly about agronomy.

The soil sample was taken from 10 holes.  In a post, Jerry recommended A&L
labs several months ago and it turned out they were the cheapest lab I could
find for the amount of testing done.  The lab had a very fast turn around
time.  Here are the results:
All numbers are in PPM unless otherwise noted.  Also, they rated the amount
of each element as either (Very Low-VL; Low-L; Medium-M; High-H; Very
High-VH)

Organic Matter=4.8%;  Phosphorus-Bray P1 ppm-P=5(VL);  K=101(M);  Mg=330(H);
Ca=2900(H);  S=11(M);  Zn=3.5(M);  Mn=33(H);  Fe=24(H);  Cu=1.7(H);
B=1.0(M);  Soil pH=6.9;  CEC-meq/100g=17.8;  Percent Base
Saturation-(%K=1.5; %Mg=15.5; %Ca=81.6; %H=1.5)

I also asked for fertilizer recommendations for peaches.  Here they
are(lbs/acre):

Lime=0;  N=65;  Phosphate-P205=100;  Potash-K20=95;  Mg=0;  S=0;  Zn=2.5;
Mn=0;  Fe=0;  Cu=0;  B=1

Here are some questions I have.  Any help would be appreciated, as well as
any comments.

-Zn, B, K, and S are all listed as Medium in amount, but the recommendations
only call for adding Zn, B, and K(Potash).  What about S?

-I thought peaches require a pH of 6.5.  I can't see that the fertilizer
recommendations would lower the pH.  Is 6.9 OK for peaches?

-What in the world is Cation Exchange Capacity (CEC)?  Is it very important?

-I only have about one acre of land and am growing fruit trees on about 1/2
of it.  Am I likely to find a Coop that will mix such a small amount of
fertilizer?  If so, any idea on what would be a fair price?  I would
probably need it bagged.  If they won't mix it for me should I just try to
buy some raw phosphate since it's most lacking in the soil?

-I've read P only moves down about 1 inch per year.  Will I likely have to
put it on every year?  Would it help to put a little extra on the first year
since it's so low?

Thanks,
Mark Angermayer
Zone 5 Kansas































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