Epsom Salt & Magnesium for Yellow Leaves
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Get the Epsom salt to apply as a low-concentration foliar spray for a quick fix, or per hectare to the soil for a lasting one — plus the magnesium supplied to correct yellowing.
Epsom salt magnesium dose
Next: dissolve 4 kg Epsom salt in 200 L water and spray on a cool, dry morning for a quick 0.4 kg Mg correction.
Magnesium is ~9.8% of Epsom salt (MgSO₄·7H₂O). Keep foliar concentration at/under 2% to avoid leaf scorch; soil application acts more slowly but lasts longer.
Epsom salt & magnesium — key facts
- Epsom salt
- magnesium sulphate, MgSO4
- Magnesium content
- ≈ 9.8% Mg
- Sulphur content
- ≈ 13% S
- Deficiency sign
- interveinal yellowing, old leaves
- Foliar mix
- ≈ 1–2% (10–20 g/L)
- Foliar effect
- fast, within days
- Soil effect
- lasting, season-long
- Privacy
- Runs in your browser; nothing uploaded
Green up yellow leaves without guessing the dose
Magnesium sits at the heart of every chlorophyll molecule, so when it runs short the older leaves yellow between their veins while the veins stay green — the tell-tale interveinal chlorosis seen on sandy, acidic and high-potassium soils. Epsom salt, magnesium sulphate at about 9.8% magnesium, is the quick remedy: sprayed on leaves at a low concentration it works within days, or worked into the soil per hectare it fixes the shortage for the season.
This tool returns the Epsom salt to apply, the magnesium that supplies, and the application mode from your spray volume and concentration or your area and per-hectare rate. Use it for a fast foliar rescue and a lasting soil correction. Pair it with the Micronutrient Spray, Foliar Urea Spray and Fertilizer (NPK) tools to balance the whole nutrition plan.
Fix yellow leaves fast
Low-concentration foliar spray works in days.
Correct it for good
Soil application feeds roots all season.
Get the dose right
Convert magnesium to Epsom salt and back.
Avoid leaf scorch
Keep foliar concentrations safely low.
Frequently Asked Questions
What does Epsom salt do for plants?+
Epsom salt is magnesium sulphate (MgSO4), a soluble source of magnesium and sulphur. Magnesium sits at the centre of the chlorophyll molecule, so it is essential for photosynthesis; supplying it corrects deficiency, greens up pale leaves and supports vigorous growth and fruiting.
How do I know my crop is short of magnesium?+
The classic sign is interveinal chlorosis on older leaves — the leaf veins stay green while the tissue between them turns yellow, because the plant moves mobile magnesium up to younger growth. It shows first on lower, older leaves, often on sandy, acidic or high-potassium soils. A leaf or soil test confirms it.
How much magnesium does Epsom salt contain?+
Magnesium sulphate heptahydrate, the usual Epsom salt, is about 9.8% magnesium and around 13% sulphur. So to supply a given amount of magnesium you need roughly ten times that mass of Epsom salt. The calculator handles this conversion both ways for you.
Foliar spray or soil application — which should I use?+
Use a low-concentration foliar spray for a quick fix when symptoms appear, because leaves absorb magnesium directly within days. Use a soil application per hectare for a lasting correction that feeds the crop through its roots over the season. Many growers do a foliar rescue first, then address the soil.
What concentration is safe for a foliar spray?+
Epsom salt foliar sprays are usually mixed at a low concentration — commonly around 1–2% solution, or roughly 10–20 grams per litre of water — to avoid leaf scorch. Spray in cool conditions, cover the foliage to run-off, and repeat every couple of weeks if needed rather than over-concentrating.
How does the calculator work?+
Choose foliar or soil mode and enter your target — a spray volume and concentration, or an area and per-hectare rate. The tool returns the Epsom salt to apply and the magnesium that supplies, using the 9.8% magnesium content of magnesium sulphate. Mode is shown so you can plan the right kind of application.
Can I use too much Epsom salt?+
Yes. Excess magnesium can unbalance soil cations and compete with calcium and potassium uptake, and strong foliar sprays scorch leaves. Only apply it where a deficiency is real — confirmed by symptoms or a test — rather than as a routine tonic, and keep foliar concentrations low.
Is Epsom salt the only magnesium source?+
No. Dolomitic lime supplies magnesium while raising pH on acid soils, kieserite is a slower-release magnesium sulphate, and compound fertilisers can include magnesium. Epsom salt is favoured for its high solubility, making it ideal for foliar sprays and fertigation where a fast, water-soluble source is needed.
Will magnesium help blossom-end rot or leaf curl?+
Magnesium deficiency causes interveinal yellowing, not blossom-end rot — that is a calcium problem, and adding magnesium can even worsen it by competing with calcium. Diagnose the actual deficiency before reaching for Epsom salt; it is a magnesium and sulphur supplement, not a cure-all.
Are the figures precise?+
They are accurate for the 9.8% magnesium content of standard Epsom salt, but real plant response depends on soil magnesium, pH, competing nutrients and how thoroughly foliage is wetted. Treat the dose as a starting point, verify deficiency with a test, and adjust based on the crop's recovery.