Xref: news7 rec.arts.bonsai:59051

I buried (in one of my large grow boxes where assorted cuttings, seedlings,
and other "stuff" also live) two small (mame/small shohin size) pots that had
heavy deposits of lime around the pot rims.
The soil was quite heavy -- a mixture of various old bonsai soils and
horse-manure compost
the compost breaks down into a very mucky substance.

The mucky substance is humic acid. I don't know the pH, but I suspect it is
very low. Exposing the lime deposits to a weak acid for months at a time would
have the expected effect.

Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)