permaculture

["robscott@freeshell.org" <robscott@freeshell.org>]

Gypsum occurs naturally as Hydrated Calcium Sulfate (CaSO4 2H2O) which
precipitated out of saline water over millions of years and was deposited 
as sediments which are mined today. Board production involves heating 
mineral gypsum to 250C to release the H20 as steam. (This is H20 from the 
age of dinosaurs!) H20 can be readded and the gypsum is thus easy to 
transport as a mineral rock, powder, or paper bound construction board.

In Northern Illinois gypsum is applied to peanut fields becuase peanuts
deplete soil calcium. Peanut plants need calcium so that the nuts can fill
the pods. Farmers export calcium every year by exporting the peanut crop.
So they apply calcium every year, but they don't apply lime (CaCO3) 
because it will raise pH. Instead, farmers use gypsum, which supplies 
calcium without altering pH. This is important because they are adding 
calcium every year. They refer to gypsum as "land plaster" !

I say it is safe to recycle gypsum board into crop soils, so long as it 
isn't treated with rot-resistant chemicals or covered with paint.

Rob Scott
Urbana Permaculture Project
Urbana, IL