Sulphate of Potash chloride-free potassium fertiliser
Sulphate of Potash chloride-free potassium for crop nutrition
Premium potassium. No chloride. No compromise.
SoilWorx Sulphate of Potash (SOP) is a high-analysis potassium fertiliser supplying 50% K2O in a chloride-free, low-salt form. It is the potassium source of choice in crop nutrition programmes where crops are sensitive to chloride, including potatoes, soft fruit, vegetables, protected crops and hops. The chloride content of cheaper muriate of potash (MOP) can damage quality, reduce yields and affect marketable output.
Sulphate of potash also provides sulphur (typically 18% SO3), making it doubly useful in sulphur-responsive crops where deficiency is now widespread following reductions in atmospheric sulphur deposition across the UK and Ireland.
Product specifications
|
Parameter
|
Value
|
|---|---|
|
Total Nitrogen
|
0.1 %w/w
|
|
P2O5
|
0.0 %w/w
|
|
K2O
|
50.4 %w/w
|
|
Sulphur (SO3)
|
Approximately 18%
|
|
Chloride content
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Chloride-free
|
|
Salt index
|
Low
|
|
Pack sizes
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1,250 kg bulk bags
|
|
Form
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Granular / mini-granular
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Why Sulphate of Potash?
Chloride-free and low salt index. Unlike muriate of potash (KCl, 60% K2O), sulphate of potash contains no chloride. Chloride can accumulate in the soil, increasing osmotic stress, reducing water uptake and, in potatoes, increasing the risk of blackspot bruising and reducing dry matter content. SOP’s low salt index also reduces the risk of fertiliser scorch on seedlings and sensitive root systems.
Sulphur bonus. The sulphate form of SOP delivers readily available sulphur alongside potassium. Sulphur deficiency has increased substantially across UK and Ireland’s arable and grassland soils in recent decades. SOP addresses both deficiencies in one application.
Which crops benefit most?
Sulphate of potash is the preferred potassium source for:
- Potatoes: prevents blackspot bruising, maintains dry matter, improves tuber quality for fresh and processing markets
- Soft fruit: strawberries, raspberries, blackcurrants and gooseberries
- Vegetables: brassicas, alliums, salads and root crops where chloride tolerance is low
- Protected crops: tomatoes, cucumbers, peppers and other high-value glasshouse crops
- Hops: chloride-sensitive perennial crop with high potassium demand
SOP vs Muriate of Potash: which to choose?
|
Factor
|
Sulphate of Potash (SOP)
|
Muriate of Potash (MOP)
|
|---|---|---|
|
K2O
|
50%
|
60%
|
|
Chloride
|
Chloride-free
|
Contains chloride (46%)
|
|
Sulphur
|
approximately 18% SO3
|
None
|
|
Salt index
|
Low
|
High
|
|
Best for
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Potatoes, soft fruit, vegetables, protected crops, hops
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Cereals, oilseed rape, grassland (where chloride is tolerated)
|
Application rates & timing
At soil K index 1, typical rates range from 175–250 kg K2O per ha, equivalent to 350–500 kg per ha of SOP. Adjust based on your soil analysis. Use our Fertiliser Calculator for crop-specific guidance.
Apply pre-planting as a base dressing for potatoes and root crops. For soft fruit and protected crops, split applications across the growing season are often more effective. Timing should be guided by soil analysis and crop demand.
SOP in SoilWorx blends
SoilWorx incorporates Sulphate of Potash into our K-Boost 3-2-17 organic NPK blend, specifically formulated for potato and root crop production. SOP can also be incorporated into bespoke custom blends through our custom manufacturing service.
Frequently asked questions
Can I use sulphate of potash on potatoes?
Yes. SOP is the preferred potassium fertiliser for potatoes. Chloride from MOP can reduce dry matter content, increase blackspot bruising and affect tuber quality, particularly for pre-pack and crisping markets. SOP delivers potassium without these risks, while the sulphur can also help with scab control.
Is SOP available as part of a blended fertiliser?
Yes. SoilWorx incorporates Sulphate of Potash into our K-Boost 3-2-17 organic NPK blend, specifically formulated for potato and root crop production. It can also be incorporated into bespoke custom blends through our custom manufacturing service.
What application rate for potatoes?
At soil K index 1, typical rates range from 175–250 kg K2O per ha, equivalent to 350–500 kg per ha of SOP. Adjust based on your soil analysis. Use our Fertiliser Calculator for crop-specific guidance.
About SoilWorx
SoilWorx is produced at the UK and Ireland’s largest organic fertiliser plant in Newry, Northern Ireland, part of a circular economy that transforms agricultural by-products into high-value fertilisers. Find out more about how we make our products.
Enquire about Sulphate of Potash
Contact our team for trade pricing and availability, or use the Fertiliser Calculator for rate guidance. Also available as part of our K-Boost 3-2-17 blend.