Potassium Sulphate Solution Grade is a fine-grind, fully water-soluble potassium sulphate (SOP) built for fertigation and foliar feeding. It carries roughly 51 to 52% soluble potash (K2O) and 18.7% sulphur (S) with very low chloride and no nitrogen, so you feed potassium and sulphur together without loading salt or chloride into the root zone. Sulphate of potash is one of the milder potassium sources, and the fine grind meters, dissolves, and injects cleanly through drip and irrigation lines with almost no residue in the tank.
As a sulphate rather than a muriate (chloride) source, this grade carries a very low salt index, well below muriate of potash (potassium chloride). That makes it a gentler choice for salt- and chloride-sensitive crops and for concentrated fertigation, and it performs across a range of soil pH, in both acidic and alkaline soils.
What potassium and sulphur do in the plant
Potassium Sulphate Solution Grade supplies two of the nutrients plants draw on most heavily, in a form that moves straight into solution.
Potassium (K2O): Potassium regulates water movement and turgor, drives the opening and closing of stomata, and activates dozens of enzymes involved in photosynthesis and in moving sugars and starches into fruit, tubers, and storage tissue. Well-supplied potassium supports firmer fruit, better sizing and finish, sugar accumulation and colour, and stronger tolerance of drought and heat, and it can help produce and hold up better through storage and transport. Demand climbs through fruit sizing and finishing, which is where a clean, soluble potassium source earns its place in a feed program.
Sulphur (S): Sulphur is a building block of amino acids and proteins, and it is needed to form chlorophyll along with several plant enzymes and vitamins. Here it is supplied as sulphate, the form plant roots take up directly. Sulphur also improves how efficiently the plant uses nitrogen, so a sulphur shortfall often shows up looking like a nitrogen shortage. Feeding sulphur alongside potassium keeps both pathways supplied at once.
Why the sulphate form
How potassium is delivered matters as much as how much you deliver. Supplying it as a sulphate carries several advantages over muriate and nitrate potassium sources.
Low chloride and salt index: Delivering potassium as a sulphate avoids the chloride that comes with muriate of potash, with chloride held to a guaranteed maximum of 1% (typically around 0.6%). It also carries the lowest salt index of the three common potash sources (sulphate, muriate, and nitrate), which makes it well suited to chloride-sensitive crops, protected cropping, and repeated fertigation, where chloride and salt can otherwise build up in the root zone.
Less leaching: Potassium sulphate is less prone to leaching than muriate or nitrate potassium sources, particularly in light, sandy soils, so more of what you apply stays in reach of the roots.
Nitrogen-free: Because it carries no nitrogen, you can raise potassium without adding nitrogen at the same time. That is useful through fruit growth and into the run-up to harvest, when you often want potassium high while nitrogen tapers off.
Works across soil pH: It performs in both alkaline and acidic soils. Its mildly acidic solution helps lower the pH right at the root surface in alkaline or salt-affected soils, which keeps phosphorus, iron, and other micronutrients more available, and that same mild acidity helps keep drip lines and emitters from scaling and clogging.
Who it's for
Potassium Sulphate Solution Grade fits growers who feed through water and want a clean, soluble potassium and sulphur source.
Fertigation and drip operations: Greenhouse, container, and market-garden growers, along with orchards and vineyards on drip, sprinkler, or centre pivot, can meter it directly into irrigation. Fast, near-complete dissolution and very low residue keep injectors and emitters clean.
Foliar programs: The fine grind goes into solution quickly for foliar sprays that top up potassium and sulphur during high-demand stages such as fruit sizing and finishing.
Salt- and chloride-sensitive crops: Low chloride and a very low salt index make it a good fit where chloride or salt buildup is a concern, including protected cropping and repeated fertigation.
Commercial cannabis: Growers running fertigated or hand-fed potassium and sulphur through bloom can use it as a soluble K and S source.
How to use
Application rates vary with soil type, crop, and growth stage, and are best set from a professional soil or tissue analysis. Warm water and continuous stirring speed dissolution; cold or poor-quality water slows it. Rates below are starting points; a soil test sets them precisely.
Home and garden
Topdressing: 25 to 50 g per cubic yard of soil, or about 0.15 to 0.25 g per gallon of soil (roughly 1 g per 5-gallon container). Work into the top 2 to 3 inches and water in. Reapply at the start of each cycle.
Liquid feed: 0.25 to 0.75 g/L. Apply to the soil. Delivers 107 to 321 ppm K. Use the low end for routine feeding, the high end during fruiting and bulking. Adds 0.3 to 0.9 mS/cm EC.
Foliar feed: 1 to 2 g/L, or about 1 tsp per 3 to 6 L, for rapid correction of potassium deficiency. The solution is naturally acidic; check the pH of your mixed spray and adjust to 5.5 to 6.5 if needed, as most source water buffers it into an acceptable range on its own. Spray early morning or evening, never in midday sun. Spot-test a few leaves and wait 48 hours before treating a full crop. Foliar feeding supplements soil potassium; it does not replace it.
Commercial fertigation
Potassium Sulphate Solution Grade is designed for injection through drip, sprinkler, and centre-pivot systems. Keep the stock solution at or below 100 g/L (10 kg per 100 L of water), the highest practical concentration, and inject to the target potassium level for your crop and growth stage. Typical delivered concentrations are 0.25 to 0.75 g/L in the final solution, supplying approximately 107 to 321 ppm K and 47 to 140 ppm S, and contributing 0.3 to 0.9 mS/cm of EC on its own.
As a guide, daily fertigation rates for field vegetables commonly fall between 1 and 8 kg/ha depending on crop and stage, while tree fruit and vine crops are typically fed to seasonal totals of roughly 150 to 500 kg/ha split across growth stages. Detailed per-crop, per-stage programs are available on request.
Mixing, water quality, and compatibility
Fill the tank to about two-thirds, add the product with continuous stirring, then top up with water and confirm it has fully dissolved before injecting. If your source water is highly alkaline (pH above 8), acidify the stock solution before adding the product. When combining with other fertilizers, dissolve Potassium Sulphate Solution Grade first, especially before adding any magnesium-containing product. It is compatible with most other soluble fertilizers within normal concentration ranges; the main exception is calcium-containing fertilizers, since calcium and sulphate combine into a low-solubility precipitate (calcium sulphate) that can foul lines. Filtering the injected solution and running a small-scale compatibility trial before a full batch are both good practice.
Guaranteed analysis:
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Soluble Potash (K2O): minimum 51% (nominal 52% grade)
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Sulphur (S): 18.7% (as sulphate)
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Chloride (Cl): maximum 1% (low chloride)
Form and particle size: Fine white powder. Sieve analysis: about 20% retained on 50 mesh (over 0.300 mm), 60 to 70% retained on 120 mesh (over 0.125 mm), and 30 to 40% passing 120 mesh (under 0.125 mm). Bulk density about 1.21 kg/L loose and 1.46 kg/L struck.
Solubility and purity: Solubility about 120 g/L in pure water at 25°C; roughly 90% dissolved within three minutes of stirring; residue 0.03% (5% solution after 10 minutes); moisture 0.02%; pH about 2.9 in a 1% solution.
Storage and handling
Store Potassium Sulphate Solution Grade sealed and dry to keep it free-flowing and fully soluble; its very low moisture content means it stays stable when kept out of humidity. Keep it away from children and pets, avoid breathing the fine dust, and rinse off any skin or eye contact after handling. Wash hands after use.
Solution grade vs the powder
This is the solution grade, made by reacting potassium chloride with sulphuric acid to yield a very pure, fast-dissolving, low-chloride potassium sulphate. That route is what makes it so well suited to fertigation, but because it is a manufactured form of potassium sulphate rather than a mined, naturally-occurring one, it is not permitted for use in organic production. For a potassium sulphate suited to organic growing, use our Potassium Sulphate powder.
