A soluble Source of Magnesium. In agriculture and gardening, magnesium sulfate is used to correct magnesium deficiency in soil (magnesium is an essential element in the chlorophyll molecule). Magnesium Sulphate is most commonly applied to potted plants, or to magnesium-hungry crops, such as potatoes, roses, and tomatoes. The advantage of magnesium sulfate over other magnesium soil amendments (such as dolomitic lime) is its high solubility. Magnesium Sulphate is used to correct plant yellowing and encourages white blooms on hydrangeas. Also excellent for using on palms.