Better Farming - October 2016

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48 Farm News First > Better Farming October 2016
Did you ever wonder what
would happen if you sent the
same soil sample to two labs?
Or if you split a sample and sent it to
the same lab as two different fields?
Or if you sampled a field and then
sampled it again a month later? How
would the results differ?
Well I have wondered and I did
those things. And more.
I became interested in soil sam-
pling when I was a teenager. Jim
O’Toole and I did a soil sampling
demonstration as part of the Central
Ontario 4-H demonstration competi-
tion. We won and advanced to
provincials. Over the years my
interest has not diminished.
I am surprised at how many
farmers do not have a soil sampling
history on every field. Part of it is
because of the secrecy and “untold”
truths about soil analysis. Even now I
can’t get analysing details from all
labs.
Over the years I have done my own
testing of the soil sampling system.
When I taught at Centralia College of
Agricultural Technology I had
students soil sample the same field.
Two members of an eight-member
team soil sampled the same 10 acres
every week. Each of these samples was
sent in as two separate samples. Thus
there were at least 16 samples from
each field over a four- to six-week
period. Of these, one-half were the
same sample split in two.
The results were interesting. There
was a significant difference among the
results. The variation was very large. I
concluded some students were
sampling deeper than others. Some
samples were not mixed well enough.
From that I learnt you should have
the same person sample the same
field every time. Better still, get a
by PAT LYNCH
CROPS:THELYNCHFILE
Testing the soil test
Why is it that if you send the same soil sample to two labs you’ll get different results?
Here, the mystery is explained.
Create a 20- to 25- year history of your soil by sampling regularly.
professional soil sampler with a set
depth to take your samples.
In the 1980s, I had summer
students sample an area about 200
feet square. This area was sampled
every week during the year (when the
season permitted you to draw a
sample) over three years. Again, the
results were amazing. There was
about a twofold change in both P