GYPSUM

[Phil_SK]

I don't use gypsum. But if you mix Plaster of Paris with water, let it set and dry and then break it up this will be the same as if you had gypsum.

[DaveW]

"Not sure that you'd really want to use plasterboard. The gypsum used to manufacture it is often a waste product of other industrial processes such as flue gas desulphurisation in power stations."

I think they still used "flue gas gypsum" it in agriculture in my original link. However as you say with industrial products you can never be sure that the composition of the product remains constant. Look at the rubbish we now get sold as John Innes composts which are nothing like the old original recipes, containing poorly rotted garden waste instead of peat. Landfill in a bag!

[Rene G]

You can get Gypsum alright, but you may have to buy a 25kg bag! I have used it for over 20 years and Cacti thrive on it if you use it wisely. I guess it helps to unlock some of the base key elerments and nutrients for the plants to absorb. Use it sparingly, I use a table spoon full to a bucket of potting medium.
Good thing about it is that it does not effect or increase the pH as lime wood.

[Roberto A]

You can get Gypsum alright, but you may have to buy a 25kg bag! I have used it for over 20 years and Cacti thrive on it if you use it wisely. I guess it helps to unlock some of the base key elerments and nutrients for the plants to absorb. Use it sparingly, I use a table spoon full to a bucket of potting medium.
Good thing about it is that it does not effect or increase the pH as lime wood.

ehhh... as I wrote before, my problem is that I can't find Gypsum (that is: natural or "agricultural" gypsum) here.... I have seen there are many quarries selling it on main-land Italy, but not on my Island... :-(

[gerald]

I have a 1kg bag, I can send you a few hundred grammes if you can paypal the postage costs. Just pm your address.