are epsom salts alkaline or acidic?
In the case of Epsom salt, for every magnesium (Mg+2) ion taken up by the roots, it gives off two hydrogen (H+1) ions, which can decrease the growing medium's pH around the root. For every sulfate (SO4-2) ion, the root releases two hydroxide (OH-1) ions, which raises the pH of the growing medium around the root.