In article ,
Chris Hogg wrote:

Can't help you with the MSDS question, but as to adding calcium
nitrate and limestone, I was always under the impression that it's
high pH caused by lime or limestone that's the problem with ericaceous
plants, not the calcium per se. One of my books on rhodos advocates
gypsum as a soil improver for rhodos and azaleas. Proper mineral
gypsum (not the plaster of Paris commonly available from builders'
merchants these days), is naturally slightly acidic, being the salt of
a weakish base and a strong acid.

That's not the reason. There is some reason that magnesium behaves
very differently from most metals, and its salts cause what is
effectively acidity. It's not just totting up the strengths, but
I don't know the details. The effect is also used in brewing.


Regards,
Nick Maclaren.