On Tue, 15 May 2012 09:07:09 -0500, Hell Toupee
wrote:

It is awfully good for the soil, though, and as you mentioned, it is a
valuable source of calcium, especially necessary for tomatoes. I
always advise people growing tomatoes in pots to add calcium to the
soil to reduce the risk of blossom-end rot.

I believe it also helps in moisture retention for the soil. When I've
cored / aerated a lawn I add some gypsum. Get it into the soil.