North American Fruit Explorers mailing list at ibiblio

["Heath Flax" <8orge.onx@gmail.com>]

Alan,
in contemplating, and also trying to read up on your soil amending
question...partly just to supplement or expand upon the numerous
suggestions and moot points made already in the answers and your
followups so far...I find, alas, that I come away mostly with just new
or additional questions.
..and also, I do, or try to do--the two not necessarily being
equal...)"my share" or maybe more,with blueberries and might have my
biases.....but I think I have come across  a couple of  "points to
ponder" which seem to be presented as simple fact, while if I add my
own commentary, not so certain as objectivity with the latter... both
being from the well known book, "Highbush Blueberry Production Guide"
{Northeast Regional Agricultural Engineering Service, 1992}
:
1.from Chapter 3, Site Selection and Preparation
page 18:
"Growers can reduce the soil pH if it is slightly above the desired
level;  however, lowering the pH of some soils can release high levels
of certain elements that can be toxic to the blueberry plant"
...my personal comments:  yes, if you feel it'd be enough pH
reduction to bring it down by one pH point,
that "probably" will be not too hard to do, unless the soil happens to
be what I think is usually known as a highly "buffered" one which
potentially can unfortunately take _many_  times the amount of
amendment, than more usual soils.  The technical term for this high
buffering situation, such as you may or may not know depending on your
approach to understanding soil matters, may be, level of "Cation
Exchange Capacity," or "C.E.C." that by chance is a high one...which
according to my reading, seems pretty hard, or impossible, to tell
without lab testing.  Likely true by mathmatical probability that.,
the "lighter" the soil, the more apt to be low C.E.C and thus
comparatively more readily pH amendable, but given all the complexity
and variation of soils, not what could really be called a sure thing.

2.from Chapter 11, Nutrient management,
page 103:
"Table 6. Deficient, sufficient, and excessive nutrient concentrations
in blueberry leaves."

...This table, covers the situation herein, for eleven nutrients, both
macro and micro, and includes (but is not limited to) most or all that
have come, and also  up in this discussion of what you may face in
your clients situation:
N; P; K; Ca; Mg; S; B; Cu; Fe; Mn; Zn.

Since my email service seems to always condense most open space I try
to create in an email, I think it'd be futile of me to try to
transcribe the chart, so I won;t go that far--and anyway, the title of
the chart, just by itself, would seem to indicate that there does
exist in blueberry growing, nutrient upper limits, as well as lower
ones...and the soils you describe, sure do seem to some very unusual
nutrient levels, apt to  appear extreme at one end of the scale or the
other, to blueberry growing.

I "do" note here, that this chart specifies "leaf" cutrient
concentrations, rather than "soil" concentrations--these latter being
something I find completely absent in this book, which to me, is if
anything something of a further cautioning about blueberry nutrition
and blueberry growing and maybe also about soils-and-growing in
general:  that plant nutrition and, by extension, perhaps soil
nutrient content, availability and absorbtion,  is so complicated that
current scientific approach about it (such as  specialized cases, e.g.
blueberries) may have only reached the symptom level (leaf analysis).
The soil level of content of nutrients and nutrient uptake may in
current practical terms just have too many variables and complexity to
allow it to have been addressed very much.

Just my take overall, of course, except for the book material included
for the sake of the facts and science side of thing.  Though, of
course, sincere "good luck" to you If you do end up experimenting and
trying your luck (and maybe learning a lot) lowering pH with something
like Sulfur (which by the way, I think is often suggested to be used
sparingly or if not sparingly, gradually, since it may be pretty harsh
stuff--I know from having probably done years and years worth of harm
to a few of my plants when my "moderate" application apparently
"burned" either the soil biota, or the blueberries fragile roots. or
both),
Unusually "conservative", though, that it may seem (to me) for me to
be concluding, and again, just my subjective "take:",  I do seem to
find myself thinking it'd  hardly seem surprising if, in perhaps
taking on this  major soil adjustment  (instead of soil replacement or
change of item to be grown), you end up with a kind of  big and
ongoing challenge.

Heathflax