What Is Sulphate of Potash Used For?

Sulphate of potash (SOP) is potassium sulphate, a straight potassium fertiliser. The supplier technical data sheet for our 25 kg bag gives a typical analysis of potassium 41% and sulphur 18%, as a general grade prill of 2 to 4 mm. This guide explains what those numbers mean, what SOP is used for, how it differs from muriate of potash and what to check before you buy.

Stock update: our 25 kg Sulphate of Potash is out of stock at the moment. Join the waiting list on its page and we will email you when it is back. It is a straight potassium and sulphur fertiliser (41% K, 18% S), and we do not currently stock another straight potassium product, so there is no like-for-like swap. If you want a general feed that includes potassium, YaraMila Complex 12-11-18 (18% K₂O, $68.20 for 25 kg) and CK 55 (marked 14-15-13, $64.35 for 25 kg) also supply nitrogen and phosphorus. Not sure what suits your plants? Call 07 5537 4585.

What is sulphate of potash used for?

Sulphate of potash is potassium sulphate (K₂SO₄). It is used as a source of two nutrients: potassium (K) and sulphur (S). The data sheet for our bag lists a typical potassium of 41% and sulphur of 18%. Fertiliser labels often show potassium as K₂O, and 41% potassium is about 49% K₂O. It is a straight fertiliser, so the analysis does not include nitrogen or phosphorus.

The plants and rates a product suits are set by the directions on its pack. We do not hold a label with directions for this product, so we do not list plants or rates here.

Sulphate of potash or muriate of potash?

Muriate of potash is potassium chloride and sulphate of potash is potassium sulphate, so in one the potassium comes with chloride and in the other with sulphate. If a plant label or your supplier tells you to avoid chloride, check which form a product uses before you buy. We do not give advice here on which plants tolerate chloride. Ask the maker of your product or call us.

What to check before you buy

• Analysis: the data sheet gives a typical potassium of 41% and sulphur of 18%. Check the pack for the analysis of the bag you receive.
• Pack size: 25 kg bag, general grade prill 2 to 4 mm.
• Directions: the only document we hold for this product is the supplier technical data sheet, so the directions for use are the ones printed on the pack.
• Your soil: a soil test shows whether your soil needs potassium.

How much to use and when

We do not give a rate or a timing here. The supplier data sheet gives the analysis and prill size, not directions for use. Read the directions and safety statements printed on the pack before use and follow the rate on the pack.

Safety

Read the full safety statements on the pack and the Safety Data Sheet (SDS) on the Sulphate of Potash product page. Keep out of reach of children.

Frequently asked questions

What is sulphate of potash? It is potassium sulphate, a straight fertiliser that supplies potassium and sulphur. The supplier data sheet for our 25 kg bag gives a typical analysis of potassium 41% and sulphur 18%.

Is sulphate of potash the same as muriate of potash? No. Muriate of potash is potassium chloride and sulphate of potash is potassium sulphate. They are different products with different analyses.

How much sulphate of potash should I use? Use the rate printed on the pack. We do not hold a label with directions for this product online, only the supplier data sheet, so we do not give a rate. A soil test shows whether your soil needs potassium.

Is the 25 kg Sulphate of Potash in stock? Not at the moment. Join the waiting list on the product page and we will email you when it is back, or call us on 07 5537 4585.

Where do I find the safety data sheet? On the Sulphate of Potash product page, under Safety Data Sheet (SDS). Read the safety statements on the pack as well.

Where to buy in the Gold Coast

Garden Nursery Products is based at Arundel on the Gold Coast. Order online with delivery from $17, priced by weight and postcode at checkout, or pick up at our Arundel store (Monday to Friday 7:30am to 4pm). Not sure which fertiliser to choose? Call us on 07 5537 4585 before you buy.

Last reviewed 12 November 2026 against the supplier technical data sheet and our product pages. Always read and follow the label.