When can MgSO4 be used as fertilizer?

Magnesium-deficient soils, magnesium-loving plants and potted plants describe the uses of MgSO4 as fertilizer. The formula in question is magnesium sulfate and shows up, perhaps most famously, in Epsom salt. It may be used with magnesium-hungry plants such as carrots, lemon trees, peppers, potatoes, roses and tomatoes because, unlike dolomitic lime, it does not change the soil pH (power of hydrogen) and, unlike limestone, it has no alkaline salts and since it is highly soluble and works in foliar feeding.