Sulphur Nutrient & Fertiliser Rate for the Crop

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.