A couple of weeks ago I wrote about the importance of soil
testing and the role of pH in plant health. I gave instructions
on how to collect a soil sample and have it tested. In the days
following, several questions came in asking for clarification or
further information. The questions are good ones. Let’s deal
with them one at a time. M.H. wrote, “After building some walls
in the basement I had several pieces of Sheetrock(tm) wallboard
left over. As you know, wallboard is made from gypsum (calcium
sulfate). Garden lime is calcium carbonate. I wondered if I
could till the wallboard into the soil to lower the acidity
instead of buying lime?” Although calcium sulfate and calcium
carbonate do seem like similar chemicals, in the soil they act
differently. It is the sulfate and the carbonate parts of the
molecules that have the potential to decrease the acidity of the
soil. It turns out that carbonate combines with positively
charged hydrogen ions set loose by calcium to form carbon
dioxide and water. Both of thos