Here are some links explaining the benefits and failures of using gypsum _http://http://walterreeves.com/landscaping/article.phtml/… (http://walterreeves.com/landscaping/article.phtml/…) _http://http://allacademic.com/meta/… 07_index.html_ (http://allacademic.com/meta/…) (a little erudite) _http://http://agry.purdue.edu/turf/tips/… (http://agry.purdue.edu/turf/tips/…) I find the third link interesting because it states that the use of gypsum's effectiveness is affected by chemicals that are already in the soil. So it will work for some but not all. I guess the clay that I got stuck with was one of the types where the gypsum worked well. Based on what other members are saying, it has been ineffective for most users so back to the drawing board ! Cherry G