Lorn, your simple mention of your pH anecdote in the other thread is understood; the particulars aren't important there.
You are correct in your first paragraph, except for your assumption that an acid must be present to liberate usable elements. It is true that that considerably more elements and compounds become more plant-available with the decrease of pH (to an extent, of course, say pH 5-5.5), but not always. Molybdenum and selenium availability, for example, increase with increasing pH.
Soil chemistry and soil biochemistry (along with everything else that is pertinent) are extremely complex - no new news there, and I hardly begin to understand all the goings on myself. Keep in mind that there are hardly any absolutes. High pH soils, for instance, still have some H+ anions, but just increasing tiny amounts. Even water (H2O) is both an acid and base, as it brakes into H+ and OHˉ ions. (Incidentally, that is why things dissolve in it so well in it.)
Thanks for expounding on your pH decreasing foray. I didn't realize that nitrogen itself acted that way, but in general, your experience is what I would have expected.
For those of you who don't know, pH is measured in a logarithmic method. Each integer change is ten times more acidic or basic, depending on whether you move up the scale (more basic) or down (more acidic). For example, pH 5 is ten times more acidic than pH 6, and pH 4 is ten times more acidic than pH 5 (and one hundred times more acidic than pH 6).
If the aim was to change a whole pH point in just six weeks, that is drastic (as you found out). Usually, my preference is to use sulfur flakes that assimilate into the soil very slowly for acidifying. Even after a year, I can find individual flakes, still not completely dissolved.
The release of "banked" nutrients (and probably not only nitrogen) is normal with big pH changes. Temperature and dried or waterlogged soils can also have major effects on soil health and chemistry.
Fortunately, for most situations there is an ingredient that works pretty much like magic in large enough quantities. - compost. It practically does it all:
--- slightly acidic where most plants prefer
--- buffers pH (helps prevent otherwise drastic pH changes)
--- great aeration (that also affects nutrient/element availability)
--- provides nutrients
--- good CEC (the ability to hold nutrients)
--- good water holding capacity
--- supports a healthy balance of soil organisms and soil micro-organisms
--- more too, that I can't think of right now
--- smells good, too
That was a good lesson, Lorn:
"Don't mess with Mother Nature."
Just help it along.
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postscript: Did I conjure up that Chiffon margarine commercial?
