Answer: Epsom salt (magnesium sulphate) is used as a source of magnesium and if applied, is used as a side-dressing or foliar spray as needed during the growing season. Certain crops, including peppers, tomatoes and roses, sometimes benefit from the additional magnesium. Rarely is there a deficiency in soils that would require the supplementing of this nutrient and, if you're using other complete fertilizers, you're already adding magnesium and sulfur.
Unless you have had a soil test done showing this deficiency or your foliage has signs of it, it's seldom applied to citrus. Citrus is however a heavy user of nitrogen, which should be applied 3 times per year, each application containing one-third of the tree's annual requirement.
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