North American Fruit Explorers mailing list at ibiblio

[Jim Fruth <jfruth@uslink.net>]

    I keep hearing folks suggesting that eggs shells be added to compost
because they contain calcium.  While that is true, perhaps 99%, or more, of
that calcium is not available to plants.  The reason being that neither
plants nor soil bacteria can take up crushed shells.  To be immediately
available, the shells must be reduced to the equivalent of dust.
    One section of my orchard used to be a garden whose owner added crushed
egg shells thinking he was adding calcium.  A scoopful of the dirt yields
hundreds or thousands of eggshell pieces and I wouldn't be surprised if 96%
of them will still be visible a thousand years from now.
    So, am I suggesting that folks stop adding eggshells to their compost?
No.  Even if eggshell pieces are not available to plants, perhaps soil
bacteria can break them down one molecule at a time.  But, if you want your
compost to get the benefit of the calcium contained in the eggshells, crush
your eggshells just as absolutely fine as you can possibly crush them.

Jim Fruth
Pequot Lakes, MN