Sulphur Nutrient & Fertiliser Rate for the Crop
Source gypsum
Product rate = target sulphur ÷ product S% — enter the target S per hectare, the fertiliser's sulphur content and the area to get the product rate per hectare and the total product to buy.
Size your sulphur dose
Next: buy 9 kg of 90%-S product and spread 22.2 kg/ha evenly across 0.4 ha.
Lower-grade sources (gypsum ~18%, ammonium sulphate ~24%) need far more product per ha than concentrated bentonite sulphur.
Sulphur fertiliser — key facts
- Product rate
- target S ÷ (product S% ÷ 100)
- Total product
- rate × area
- Gypsum
- ≈ 15–18% S
- Ammonium sulphate
- ≈ 24% S
- Elemental sulphur
- ≈ 90–100% S
- Typical target
- ≈ 15–40 kg S/ha
- Uptake form
- sulphate
- Privacy
- Runs in your browser; nothing uploaded
Turn a sulphur target into bags to spread
A recommendation gives sulphur as kg S per hectare, but the bag is only part sulphur — so you divide the nutrient target by the product's sulphur fraction to get the real weight of product to spread. Want 30 kg S/ha from an 18% product? That's 30 ÷ 0.18 ≈ 167 kg/ha. Skip this conversion and you under-apply badly, leaving crops sulphur-short with pale leaves and poor protein and oil.
This tool gives the product rate per hectare, the total product over the area, the area and the target sulphur from the target S/ha and the product's sulphur percentage. Use it to order the right number of bags and set the spreader. Pair it with the Fertiliser Blend, Nutrient Removal and Lime Requirement tools for a full nutrition plan.
Nutrient to product
Convert kg S/ha into kg of fertiliser.
Buy the right amount
Total product across the whole area.
Any sulphur source
Gypsum, ammonium sulphate or elemental S.
Avoid deficiency
Apply enough to match the tested target.
Frequently Asked Questions
How is the sulphur fertiliser rate calculated?+
By dividing the nutrient target by the product's nutrient content: product rate (kg/ha) = target sulphur (kg S/ha) ÷ (product S% ÷ 100). For example, to apply 30 kg S/ha using a fertiliser that is 18% S, you need 30 ÷ 0.18 ≈ 167 kg of product per hectare. Multiply that rate by the field area to get the total product to buy.
Why divide by the product's sulphur percentage?+
Because fertiliser bags are sold as product, not as pure nutrient. A bag is only part sulphur — the rest is calcium, nitrogen, potassium or a carrier. Dividing the nutrient you want by the fraction that is sulphur converts a nutrient target into the actual weight of product to spread. Forgetting this step badly under-applies the nutrient.
What sulphur percentages do common products have?+
Roughly: elemental sulphur 90–100% S, gypsum (calcium sulphate) 15–18% S, ammonium sulphate 24% S, single superphosphate 11–12% S, sulphate of potash about 17–18% S, and bentonite sulphur near 90% S. Always use the actual analysis on the bag, since blends and grades vary; enter that figure for an accurate rate.
How much sulphur does a crop need?+
It depends on the crop and soil. Many field crops respond to roughly 15–40 kg S/ha, with oilseeds, brassicas and legumes among the hungriest because sulphur builds protein and oil. A soil or tissue test, or a local recommendation, gives the target S/ha to enter; the calculator then turns that into a product rate.
Is elemental sulphur the same as sulphate sulphur?+
No. Plants take up sulphur as sulphate, which is immediately available, so sulphate products (gypsum, ammonium sulphate) act this season. Elemental sulphur must first be oxidised by soil microbes to sulphate, which takes weeks to months and depends on warmth, moisture and fineness — so it is slower-release. The rate maths is the same, but timing differs.
How do I get the total product to buy?+
Multiply the product rate per hectare by the field area in hectares. The calculator shows both the per-hectare rate and the total product across your area, so you can order whole bags. Round up to the next bag and keep a little spare for calibration and overlap.
Does sulphur affect soil pH?+
Elemental sulphur acidifies soil as it oxidises, which is why it is also used to lower pH on alkaline soils — a useful side effect or a caution depending on your soil. Sulphate forms like gypsum are pH-neutral and supply sulphur without acidifying. Choose the product to match both your sulphur and your pH goals.
Can I use this for other single nutrients too?+
The same target ÷ content logic works for any single nutrient — phosphorus, potassium, magnesium and so on — as long as you enter that nutrient's target and the product's percentage of it. This tool is set up for sulphur; for compound fertilisers you would run the calculation for each nutrient and reconcile the rates.
Are the figures precise?+
They are accurate for the nutrient maths, but the field result depends on the real bag analysis, spreader calibration, and how much applied sulphur is actually taken up versus leached, especially the mobile sulphate form. Use the rate to order and set the spreader, then verify with tissue testing during the season.
What happens if I apply too little or too much sulphur?+
Too little leaves crops sulphur-deficient — pale young leaves, poor protein and oil, and reduced yield, since sulphur cannot move freely from old tissue. Too much wastes money and, with sulphate, can leach to groundwater, while excess elemental sulphur over-acidifies soil. Matching the rate to a tested target avoids both.