"Epsom salt is neutral in pH value and has no effect on soil pH levels when applied to soil in dry application or as drench"
"Magnesium availability, which is linked to soil pH levels, is equally as important as magnesium levels. Soil pH levels are a measure of hydrogen ions in soil, with high concentrations of hydrogen representative of acidic soils. When soil has low pH levels, magnesium is generally deficient. However, soils with pH levels above 7.0 can have adequate magnesium, but the magnesium cannot be used by plants because of competition from calcium and potassium. Although soil amendment with elemental sulfur lowers soil pH levels through the release of hydrogen ions into the soil, Epsom salt does not release an increase in hydrogen ions, so it has no effect on pH."
"In almost all cases, Epsom salt has little influence on the pH of the growing medium."
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. So what does this mean? In most cases, a plant will take up the same number of magnesium ions as sulfate ions so the net result is that there is no change in the pH of the growing medium around the plant root.
Epsom salt is 10 percent magnesium and 13 percent sulfur,
