Magnesium Sulphate (Epsom salts)
Magnesium Sulphate, also called Epsom salts, is a soluble salt that supplies magnesium and sulphur, 10.00% magnesium and 13.00% sulphur. It suits growers correcting a magnesium deficiency on flowering, fruiting or vegetable crops, as a foliar spray or through the soil.
At a glance
- Type: soluble mineral salt (amendment)
- Supplier certificate on file: BioGro licence 297. See the certificate and its dates.
- Analysis: magnesium 10.00%, sulphur 13.00%
- Use for: correcting magnesium deficiency on flowering, fruiting and vegetable crops
- Rate: foliar 110 g (6 tablespoons) per 10 litres of water once a month
What it is
Magnesium sulphate heptahydrate, the crystalline salt sold as Epsom salts. It dissolves fully in water, so it is quick acting as a soil drench or foliar spray and does not change soil pH.
What it does
- Magnesium is the atom at the centre of chlorophyll, so a shortage shows as yellowing between green veins on the older leaves first.
- Magnesium is also a cofactor for many plant enzymes, including those involved in energy transfer and sugar movement.
- The sulphate half supplies sulphur, used for proteins, oils and flavour compounds.
- Because it is fully soluble it corrects a deficiency faster than dolomite lime, which is the slow, pH raising magnesium source.
Analysis
- Sulphur (S) 13.00%
- Magnesium (Mg) 10.00%
How to use
- Foliar spray: 6 tablespoons (110 g) per 10 litres of water once a month.
- For more frequent use, cut the dose to 3 tablespoons (55 g) per 10 litres of water once a week.
- Spray with the lights off or in the cool of the day and wet both sides of the leaf.
Watch out
Magnesium competes with potassium and calcium for uptake, so adding magnesium a soil does not need can induce a potassium or calcium shortage. Yellowing between the veins has other causes too; confirm with a soil or leaf test before treating. Magnesium sulphate does not lift pH; if the soil is acid and short of magnesium, dolomite lime does both jobs.
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Handling and storage
- Wear a mask to avoid inhaling particles and open in a well ventilated area.
- Wear gloves and eye protection, and wash hands after use.
- Once opened, keep sealed and dry.
- If ingested, or if the product comes into contact with eyes or skin irritation is present, rinse the area well and call the National Poisons Centre on 0800 POISON (0800 764 766).
Shipping and returns
We ship nationwide across New Zealand. Orders are usually dispatched within 1 to 2 business days and rural delivery can take longer. Unopened products can be returned within 30 days.
