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text-transform: none; white-space: normal; widows: 2; wor The comments below seem puzzling at first sight. Reflecting DW's comment (who seems to be knowledgeable about soil chemistry), how is it that CaSO4.2H2O (gypsum) could act as a buffer for anything? Calcium sulphate dihydrate is slightly soluble in water, and neither the completely dissociated Ca or SO4 ions produced from the salt in solution would be expected to have buffering properties, or am I missing something? Is it that the calcium releases something from its interaction with some soil component, and that this indirect effect can then produce some buffering? Gypsum apparently has been used, in the past at least, to enhance crop growth (wheat), but I'm guessing that this effect could be due to fertilizing supplementation of either low calcium or low sulphate (calcium is involved in lots of cell functions) -- something other than buffering. It would be interesting to hear some detail on both counts: how any buffering effect from dissolved gypsum is thought to come about, and how agricultural application of gypsum can sometimes increase crop yield. Maybe someone knows? Steve, Halifax ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Quoting Doug Linzey <doug.linzey@gmail.com>: > On 15/11/2011 7:38 PM, Dusan Soudek wrote: >> As minerals go, gypsum is probably environmentally the most >> benign one there is. It even neutralizes the acid rain that is >> ruining our Atlantic salmon, speckled trout, and other fish >> populations. > (& Doug Linzey wrote) If you have to have a mine in your back yard, gypsum would be a good choice. It's a pretty benign mineral. The walls of our houses are made of it. It's in some of the food we eat. It's a common soil additive. And to address Dusan's last point, it is a salt with buffering properties: it can raise the pH of acidic soils and lower the pH of alkaline soils...
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