Paul Parent, a respected (and degreed) horticulturist recommends gypsum.
See http://www.paulparent.com and search for "gypsum". Here's one quote
from his page.
Clean your gardens of branches, leaves, and dead foliage you forgot to
remove in the fall from your plants. It's also a good time to apply
limestone if your soils tend to be on the acid side and moss is a problem.
If your soil is heavy and water seems to sit there, apply some
garden gypsum to soften the soil and improve drainage.



"RoyDMercer" wrote in message
...
Actually it's a myth that gypsum will break down clay soils. Gypsum is
useful for some things like reducing the salt content in soil, but is
almost
never needed for residential use.

The most effective way to improve clay soil is by adding organic material.

"William W. Plummer" wrote in
message
news:EPjfc.38014$wP1.144408@attbi_s54...
That's exactly what gypsum is for. It binds to the clay and allows
water
to
get in to the soil.

"Tyshun Hampton" wrote in message
...
I have hard soil im my garden. When it gets wet its sticky and very
hard
to
manage. Should I remove most of the soil I have now and replace it
with
some
store brought topsoil? or can I add anything to my soil to correct
this?