Be careful with mushroom compost - or how to kill a citrus tree

My citrus never grew well and I always thought it is a lack of something. I applied blood and bone and Epsom salt and and and....
But the reason was not that there was something missing, the reason was an excess of salt.
I used mushroom compost in quantity because our soil is non existent. What I did not know that mushroom compost contains quite some
salt and citrus hate salt. Mushroom compost contains some nasties too. Now I go VERY easy on mushroom compost.