Q: Understanding a Soil Anaylsis
Question 1:
Thanks very much for getting back to me and for being available to
have a look at my soil report. Below I’ve tried to outline my
concerns and what I’ve done, and typically do, to my garden beds.
I’m attaching my current soil analysis report (dated 2008). I’m also
attaching the reports that I had done for the same beds for the
previous three years, in case you wanted to be able to compare.
I’m most concerned with my soil pH being 7.5. I don’t know why it
would be so high; in the past three years, it has ranged between 6.4
and 7.1, and I haven’t done anything differently this year.
I’m also concerned about my K, Mg and Ca being too high. All three
have risen over the past four years.
In contrast, my CEC has also risen; it started at 9.7 when the beds
were new, and is now at 23, which is good. And my sodium/salinity
levels have dropped from 2007, when they were too high.
My sulphur level apparently is adequate (according to PVFS’s
“Understanding Your Soil Analysis Report,” which I’ve studied), but my
understanding is that I could use sulphur to lower the pH.
Finally, among the trace minerals, Manganese (Mn) always shows up in
my garden at around 2 or 3 ppm, while Boron has been rising over the
years to it now being 2.6, which apparently is quite high.
Just after sending in my soil sample (end of February), I applied and
watered in 50 lbs of CalCM+ (gypsum) to my 1,000 sq. feet of beds.
CalCM+ is apparently 18.6% sulphur and 23.2% calcium. I could try
another soil test now, but it might be too early for any changes to
show.
FYI, I typically amend my soil each year with good-quality compost
(New Era, last year), bat guano for nitrogen, and azomite and kelp
algit for trace minerals. I also do soil soaks throughout the growing
season of Omega 6-6-6/1-5-5 and Algamin, and compost tea. I also
apply gypsum in the winter to lower the sodium. I also typically grow
a cover crop, but did not this winter; I just covered my beds with
straw.
So that’s probably more information than you needed or wanted, but
there you have it.
Many thanks once again!
Answer 1:
Seems like you are doing a great job fertilizing and ensuring build up
of organic matter! One thought I have is that you don’t need to apply
Azomite every year, especially if you also use kelp (skip a couple of years).
Your report indicates that you have more than enough trace elements (except
Manganese), so I would hold off for a few years on the Azomite. I
wrote a bit about what happens when there’s too many micronutrients in the
soil on our blog, if you want to check it out here.
You can find a really informative web page about Mn- here.
Your question about sulfur is a good one, because the Mn deficiency
could be tied to your high pH (Mn could be there, but tied up) and the fact
that your sulfur level is also high makes it difficult to assess what to do. As
far as I understand, the more pressing matter is getting your pH where it should be. That is, the Sulfur content isn’t as important as pH, but still use
caution when applying Sulfur so that it doesn’t reach toxic levels.
I’m somewhat concerned about your very high levels of Phosphorus and
Potassium. You might consider growing corn and potatoes now, because
they will use up some of the excess. Also if you plant Sweet Clover as a
cover crop this winter (but don’t till it into the soil, just cut it down),
that will take out some of the excess as well.
Thank you for growing organically
Question 2:
Thanks for the reply, and for the interesting links. Indeed a good
idea to back off on the Azomite!
I guess I’m still not clear as to what I should do at this point about
the high pH. As I mentioned, I put out 50 lbs of gypsum (CalCM+) near
the end of February. Should that take care of it? Would another soil
test show any difference?
Answer 2:
Something I did not talk about is the fact that as K, Mg, and Ca (which
are considered “Base” cations) break down through weathering and are
released, they raise pH. The levels of these minerals in your soil are so
high it’s no wonder the pH continues to rise! Until those levels are
brought down, the pH will be alkaline. I would suggest that you do what you
can to leach out those excesses (lots of corn and potatoes!) and hopefully
the pH will balance out. The gypsum you recently applied might help for this
season, but perhaps take another soil test next season. You might consider
also using Soil Sulfur if your pH continues to increase.
Have a good day!
Tags: alkaline, Ca, K, Mg, Mn, pH, phosphorus, Potassium, soil test, sulfur
