Magnesium sulphate is a secondary nutrient and is used to correct magnesium deficiency in the soil. Magnesium sulphate also improves nitrogen and phosphorous uptake by crops. It is best for crops that required magnesium-rich soil for growth, it is also widely used in pot mixes too. Magnesium is the central atom of chlorophyll. Magnesium is necessary to achieve high concentrations of starch in potatoes, sugar beet and fats in oil seeds.