{"product_id":"sulphate-of-potash","title":"Sulphate of Potash","description":"\u003c!-- Dr Forest — Sulphate of Potash Product Page — Design System v1.0 (granulate only) --\u003e\n\u003c!-- Prefix: sp --\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cstyle\u003e\n  .drf-wrap *, .drf-wrap *::before, .drf-wrap *::after { box-sizing: border-box; margin: 0; padding: 0; }\n  .drf-wrap { font-family: 'Jost', sans-serif; font-weight: 400; color: #2c2c2c; font-size: 14px; line-height: 1.65; width: 100%; max-width: 100%; overflow: hidden; }\n  :root {\n    --drf-grn:        #1B3D2F;\n    --drf-grn-dark:   #0F2A1F;\n    --drf-grn-light:  #E8F0EB;\n    --drf-grn-mid:    #4a7a5e;\n    --drf-cream:      #F5F2EC;\n    --drf-gold:       #C5A55A;\n    --drf-gold-light: #FAF7F0;\n    --drf-muted:      #3A4A40;\n    --drf-white:      #FFFFFF;\n    --drf-border:     #d4cfc5;\n  }\n  .drf-wrap h2 { font-family: 'Cormorant Garamond', serif; font-weight: 400; font-size: 1.9em; color: var(--drf-grn); line-height: 1.25; 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background: var(--drf-grn-light); border-bottom-color: var(--drf-grn); font-weight: 700; }\n  #drf-sp-tab1:checked ~ .drf-panels #drf-sp-panel1,\n  #drf-sp-tab2:checked ~ .drf-panels #drf-sp-panel2,\n  #drf-sp-tab3:checked ~ .drf-panels #drf-sp-panel3,\n  #drf-sp-tab4:checked ~ .drf-panels #drf-sp-panel4 { display: block; }\n\n  \/* CALLOUTS *\/\n  .drf-callout { background: var(--drf-grn-light); border-left: 3px solid var(--drf-grn); padding: 1em 1.2em; margin: 1.2em 0; }\n  .drf-callout-gold { background: var(--drf-gold-light); border-left-color: var(--drf-gold); }\n  .drf-callout p:last-child { margin-bottom: 0; }\n  .drf-callout-title { font-size: 0.72em; font-weight: 600; letter-spacing: 0.18em; text-transform: uppercase; color: var(--drf-grn); margin-bottom: 0.4em; display: block; }\n  .drf-callout-gold .drf-callout-title { color: var(--drf-gold); }\n  .drf-callout-dark { background: var(--drf-grn-dark); border-left: 3px solid var(--drf-gold); padding: 1.1em 1.3em; margin: 1.2em 0; 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border-bottom: 1px solid var(--drf-gold); }\n  .drf-uses li:nth-child(even) { border-bottom-color: var(--drf-grn); }\n  .drf-uses li:last-child { border-bottom: none; }\n  .drf-uses li strong { color: var(--drf-grn); }\n\n  \/* COMPARISON BOXES *\/\n  .drf-compare { margin: 1.2em 0; }\n  .drf-compare-box { border: 1px solid var(--drf-border); padding: 1em 1.2em; margin-bottom: 0.8em; background: var(--drf-grn-light); }\n  .drf-compare-box h4 { margin-top: 0; color: var(--drf-grn); text-transform: none; letter-spacing: 0; font-size: 1.1em; font-family: 'Cormorant Garamond', serif; font-weight: 400; border-bottom: 1px solid var(--drf-gold); padding-bottom: 0.4em; margin-bottom: 0.6em; }\n\n  \/* PULL QUOTE *\/\n  .drf-pullquote { font-family: 'Cormorant Garamond', serif; font-style: italic; font-size: 1.3em; color: var(--drf-grn); text-align: center; line-height: 1.4; max-width: 90%; margin: 1.4em auto; padding: 0.8em 0; border-top: 1px solid var(--drf-gold); border-bottom: 1px solid var(--drf-gold); }\n\n  \/* FAQ *\/\n  .drf-faq { border-bottom: 1px solid var(--drf-border); }\n  .drf-faq:last-child { border-bottom: none; }\n  .drf-faq input[type=\"checkbox\"] { display: none; }\n  .drf-faq-q { display: flex; justify-content: space-between; align-items: center; padding: 0.8em 0; cursor: pointer; font-weight: 500; color: var(--drf-grn); font-size: 0.95em; }\n  .drf-faq-q::after { content: '+'; font-size: 1.2em; font-weight: 300; color: var(--drf-gold); width: 1.5em; height: 1.5em; border-radius: 0; border: 1px solid var(--drf-gold); background: var(--drf-white); display: flex; align-items: center; justify-content: center; flex-shrink: 0; margin-left: 0.6em; }\n  .drf-faq-a { max-height: 0; overflow: hidden; transition: max-height 0.3s ease; font-size: 0.92em; color: var(--drf-muted); line-height: 1.7; }\n  .drf-faq-a \u003e div { padding: 0 0 1em; }\n  .drf-faq input:checked ~ .drf-faq-q::after { content: '−'; background: var(--drf-grn); color: #fff; border-color: var(--drf-grn); }\n  .drf-faq input:checked ~ .drf-faq-a { max-height: 700px; }\n\n  \/* REFERENCES *\/\n  .drf-refs { font-size: 0.78em; color: var(--drf-muted); line-height: 1.5; margin-top: 1.5em; padding-top: 0.8em; border-top: 1px solid var(--drf-border); }\n  .drf-refs h4 { color: var(--drf-muted); }\n  .drf-refs ol { padding-left: 1.4em; margin: 0; }\n  .drf-refs li { margin-bottom: 0.3em; }\n\n  \/* HAIRLINE RULE *\/\n  .drf-sep { border: none; border-top: 1px solid var(--drf-gold); width: 200px; margin: 1.5em auto; }\n\u003c\/style\u003e\n\u003cdiv class=\"drf-wrap\"\u003e\n\u003cdiv class=\"drf-tabs-wrap\"\u003e\n\u003cinput checked id=\"drf-sp-tab1\" name=\"drf-sp-tabset\" type=\"radio\"\u003e \u003cinput id=\"drf-sp-tab2\" name=\"drf-sp-tabset\" type=\"radio\"\u003e \u003cinput id=\"drf-sp-tab3\" name=\"drf-sp-tabset\" type=\"radio\"\u003e \u003cinput id=\"drf-sp-tab4\" name=\"drf-sp-tabset\" type=\"radio\"\u003e\n\u003cdiv class=\"drf-tab-labels\"\u003e\n\u003clabel for=\"drf-sp-tab1\"\u003eOverview\u003c\/label\u003e \u003clabel for=\"drf-sp-tab2\"\u003eThe Science\u003c\/label\u003e \u003clabel for=\"drf-sp-tab3\"\u003eHow to Use\u003c\/label\u003e \u003clabel for=\"drf-sp-tab4\"\u003eFAQ\u003c\/label\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-panels\"\u003e\n\u003cdiv class=\"drf-panel\" id=\"drf-sp-panel1\"\u003e\n\u003ch2\u003eOrganic sulphate of potash — 50% K₂O chloride-free potassium \u0026amp; 18% sulphur\u003c\/h2\u003e\n\u003cdiv class=\"drf-badge-row\"\u003e\n\u003cspan class=\"drf-badge drf-badge-green\"\u003e50% K₂O Potash\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003e18% Sulphur\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003eChloride-Free\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003eLow Salt Index\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003eCertified Organic Input\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003eRecyclable Packaging\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cp\u003eSulphate of potash is a chloride-free potassium fertiliser — 50% K2O plus 18% sulphur — used as a high potash feed for fruit, flowers and roots. Potassium drives sugar transport, fruit ripening, flower colour, drought tolerance and disease resistance. Most budget potash supplies it as potassium chloride, which builds up in soil and damages sensitive crops. Dr Forest's is naturally mined potassium sulphate (K₂SO₄), certified for use in organic production under Regulation (EC) 834\/2007 and handmade in small batches in Stockport.\u003c\/p\u003e\n\u003cp\u003eAt 50% K₂O and 18% sulphur this isn't a diluted compound or a blend — it's pure potassium sulphate in a uniform granulate that spreads evenly and dissolves on contact with soil moisture. Two essential macronutrients, immediately available, with no chloride, no nitrogen and no phosphorus to upset a carefully balanced feeding programme.\u003c\/p\u003e\n\u003cdiv class=\"drf-stats\"\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e50%\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eK₂O (Potash)\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e18%\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eSulphur (S)\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e0%\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eChloride\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e0-0-50\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eNPK Analysis\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003ch3\u003eWhat sulphate of potash is used for in the garden\u003c\/h3\u003e\n\u003cul class=\"drf-uses\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eFruiting and flowering crops\u003c\/strong\u003e — potassium regulates sugar transport, speeds ripening and intensifies flower colour; essential for tomatoes, strawberries, peppers, roses and all fruiting plants\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlavour and quality\u003c\/strong\u003e — research consistently links potassium sulphate to higher soluble sugars, vitamin C and dry matter than untreated controls\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eChloride-sensitive crops\u003c\/strong\u003e — berries, grapes, potatoes, tomatoes, citrus and salad crops all perform better on a sulphate-based source that avoids chloride build-up\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDrought and frost resistance\u003c\/strong\u003e — potassium controls stomatal opening and cell turgor, cutting water loss and improving survival in temperature extremes\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDisease resistance\u003c\/strong\u003e — adequate potassium strengthens cell walls and activates plant defence enzymes, lowering susceptibility to fungal and bacterial problems\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSulphur supply\u003c\/strong\u003e —  18% sulphur supports amino acid synthesis, chlorophyll production and nitrogen use; particularly important for brassicas and alliums\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLawns and turf\u003c\/strong\u003e — potassium hardens turf for winter and improves drought tolerance and spring green-up without an excess-nitrogen flush\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBalancing NPK feeds\u003c\/strong\u003e — zero nitrogen and zero phosphorus make it ideal for lifting the K of any feeding programme without touching the N or P\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eWhy sulphate of potash instead of muriate of potash?\u003c\/h3\u003e\n\u003cdiv class=\"drf-compare\"\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eSulphate of potash (K₂SO₄) — this product\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003e50% K₂O — high-concentration, chloride-free potassium\u003c\/li\u003e\n\u003cli\u003e18% sulphur — a second essential macronutrient in every application\u003c\/li\u003e\n\u003cli\u003eAlmost zero chloride — safe for sensitive fruit and veg\u003c\/li\u003e\n\u003cli\u003eLow salt index — minimal osmotic stress on roots\u003c\/li\u003e\n\u003cli\u003eCertified for use in organic production under Regulation (EC) 834\/2007\u003c\/li\u003e\n\u003cli\u003eSulphate-S improves nitrogen uptake efficiency\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eMuriate of potash (KCl)\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003e60% K₂O — more potassium per kg, but at a cost\u003c\/li\u003e\n\u003cli\u003e47% chloride — accumulates in soil and the root zone over time\u003c\/li\u003e\n\u003cli\u003eNo sulphur — delivers a single nutrient\u003c\/li\u003e\n\u003cli\u003eHigher salt index — greater risk of root burn and osmotic stress\u003c\/li\u003e\n\u003cli\u003eLinked to lower starch, dry matter and vitamin C in potatoes (Koch et al., 2022)\u003c\/li\u003e\n\u003cli\u003ePoorly suited to containers and tunnels where leaching is limited\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-callout\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eHandcrafted in Stockport\u003c\/span\u003e\n\u003cp\u003eEvery Dr Forest product is made by hand in small batches at our workshop in Stockport, Greater Manchester. Recyclable packaging throughout, ingredients chosen for quality rather than cost, and no slaughterhouse by-products in this product.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-panel\" id=\"drf-sp-panel2\"\u003e\n\u003ch2\u003eThe science of potassium and sulphur in plant nutrition\u003c\/h2\u003e\n\u003ch3\u003ePotassium: the quality nutrient\u003c\/h3\u003e\n\u003cp\u003ePotassium is the most abundant cation in plant tissue and the single most important nutrient for fruit quality. It never becomes part of an organic molecule — instead it works as a free ion, regulating water pressure, activating over 60 enzymes, balancing electrical charge and moving sugars from leaves into developing fruit. Plants short of potassium produce smaller, blander fruit with poorer shelf life and weaker resistance to disease and stress.\u003c\/p\u003e\n\u003cp\u003eUnlike nitrogen, which drives leafy growth and is easily over-applied, potassium can't really be made excessive in a practical garden. It is the nutrient most often under-supplied in container growing and intensive vegetable production.\u003c\/p\u003e\n\u003cdiv class=\"drf-pullquote\"\u003ePotassium decides size, flavour and shelf life — not just yield.\u003c\/div\u003e\n\u003chr class=\"drf-sep\"\u003e\n\u003ch3\u003eWhy the potassium source matters\u003c\/h3\u003e\n\u003cp\u003eRoughly 96% of the world's potassium fertiliser is sold as potassium chloride, or muriate of potash. It's cheap and concentrated. But the chloride ion it carries isn't inert — it accumulates in soil, raises salinity and damages sensitive crops directly. The choice between chloride and sulphate as the accompanying anion has measurable consequences for crop quality.\u003c\/p\u003e\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e01\u003c\/span\u003e\n\u003ch4\u003ePotato quality — starch, sugars \u0026amp; vitamin C\u003c\/h4\u003e\n\u003cp\u003eA two-year field trial by Koch et al. (2022) compared K₂SO₄ and KCl on two potato cultivars. Potassium sulphate held higher starch and ascorbic acid (vitamin C), while KCl-treated tubers built up more reducing sugars in storage — the precursors to acrylamide during cooking. The KCl treatment also carried more lipid-derived off-flavour compounds.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e02\u003c\/span\u003e\n\u003ch4\u003eFruit weight \u0026amp; soluble solids\u003c\/h4\u003e\n\u003cp\u003eIn pineapple, swapping KCl for K₂SO₄ at 20% less total potassium produced larger fruit and better bromatological quality, including total soluble solids and vitamin C (Arias-Vázquez et al., 2018). The sulphate-fed plants won on less total potassium — source matters as much as quantity.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e03\u003c\/span\u003e\n\u003ch4\u003eChloride accumulation \u0026amp; root-zone salinity\u003c\/h4\u003e\n\u003cp\u003ePotassium sulphate adsorbs to soil particles more strongly than KCl, so it leaches less (Tisdale et al., 1999). In containers, where leaching is limited, that matters. Chloride from KCl accumulates in the root zone, raising osmotic potential and reducing water uptake. Sulphate ions don't carry that risk.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e04\u003c\/span\u003e\n\u003ch4\u003eSulphur, the fourth macronutrient\u003c\/h4\u003e\n\u003cp\u003eSulphur is essential for the amino acids cysteine and methionine — without them protein synthesis stalls. It's a structural part of coenzyme A and thiamine and is needed for chlorophyll. Sulphur deficiency caps nitrogen efficiency: adding N to a sulphur-short soil gives diminishing returns. Every application here delivers 18% S alongside the potassium.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e05\u003c\/span\u003e\n\u003ch4\u003ePotassium \u0026amp; disease resistance\u003c\/h4\u003e\n\u003cp\u003eAdequate potassium thickens cell walls, increases cuticle wax and activates pathogenesis-related (PR) proteins. Potassium-sufficient plants show fewer fungal problems including powdery mildew, botrytis and fusarium wilt. The mechanism is mostly physical — stronger walls are harder for fungal hyphae to penetrate — backed by faster enzymatic defence.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e06\u003c\/span\u003e\n\u003ch4\u003ePotassium \u0026amp; water regulation\u003c\/h4\u003e\n\u003cp\u003ePotassium is the main ion controlling stomatal aperture. When it's adequate, guard cells close stomata quickly under water stress to cut transpiration — which makes potassium the single most important nutrient for drought tolerance. Well-supplied plants also recover faster from frost, since potassium lowers the freezing point of cell sap and protects membranes.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-refs\"\u003e\n\u003ch4\u003eScientific references\u003c\/h4\u003e\n\u003col\u003e\n\u003cli\u003eKoch, M. et al. (2022). Comparison of the effects of potassium sulphate and potassium chloride fertilisation on quality parameters of potato tubers. \u003cem\u003eFrontiers in Plant Science\u003c\/em\u003e, 13, 920212.\u003c\/li\u003e\n\u003cli\u003eArias-Vázquez, E.L. et al. (2018). Effects of potassium chloride and potassium sulphate on 'MD-2' pineapple fruit yield and quality. \u003cem\u003eActa Horticulturae\u003c\/em\u003e.\u003c\/li\u003e\n\u003cli\u003eTisdale, S.L. et al. (1999). \u003cem\u003eSoil Fertility and Fertilizers\u003c\/em\u003e. 5th ed. Prentice Hall.\u003c\/li\u003e\n\u003cli\u003eMengel, K. \u0026amp; Kirkby, E.A. (2001). \u003cem\u003ePrinciples of Plant Nutrition\u003c\/em\u003e. 5th ed. Kluwer Academic.\u003c\/li\u003e\n\u003cli\u003eSharma, U.C. \u0026amp; Sud, K.C. (2001). Effect of potassium sources on potato yield and quality in acidic and alluvial soils. \u003cem\u003eJ. Indian Potato Assoc.\u003c\/em\u003e, 28, 70–71.\u003c\/li\u003e\n\u003cli\u003eKumar, P. et al. (2004). Effect of sulphate and muriate of potash on quality of potato. \u003cem\u003eAnnals of Agricultural Research\u003c\/em\u003e, 25(3).\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-panel\" id=\"drf-sp-panel3\"\u003e\n\u003ch2\u003eHow to use sulphate of potash: application rates \u0026amp; guide\u003c\/h2\u003e\n\u003cdiv class=\"drf-callout drf-callout-gold\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eMeasuring \u0026amp; spreading\u003c\/span\u003e\n\u003cp\u003eA level teaspoon of granulate is roughly \u003cstrong\u003e5g\u003c\/strong\u003e. The granules are free-flowing — broadcast by hand or spreader, top-dress around plants, or stir into compost and potting mixes. Always water in after a soil application so the potassium reaches the root zone.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003ch3\u003eApplication rates — soil\u003c\/h3\u003e\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eSoil mix — potting and container preparation\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 1–2g per litre of compost  |  \u003cstrong\u003eWhen:\u003c\/strong\u003e at planting\u003c\/div\u003e\n\u003cp\u003eMix thoroughly through compost or potting soil before planting. Provides baseline potassium and sulphur for the first 4–6 weeks. Ideal for tomatoes, peppers, strawberries and other fruiting crops.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eTop dressing — established containers\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 2–6g per 10-litre pot  |  \u003cstrong\u003eFrequency:\u003c\/strong\u003e every 4–6 weeks in the growing season\u003c\/div\u003e\n\u003cp\u003eScatter granules evenly over the soil surface and water in well. Use the higher rate for heavy-fruiting crops at peak production. Work lightly into the top centimetre of soil where you can.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eOutdoor beds and borders\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 20–50g per m²  |  \u003cstrong\u003eFrequency:\u003c\/strong\u003e every 6–12 weeks, spring to autumn\u003c\/div\u003e\n\u003cp\u003eBroadcast evenly across the soil surface and water in. Lower rate for maintenance; higher rate for heavy-fruiting crops, new plantings, or where soil potassium is known to be low.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eLawns and turf\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 20–35g per m²  |  \u003cstrong\u003eFrequency:\u003c\/strong\u003e twice a year — spring and autumn\u003c\/div\u003e\n\u003cp\u003eApply in spring for active growth and in autumn to harden turf for winter. Water in immediately. Potassium improves drought tolerance, wear resistance and winter colour.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003ch3\u003eDissolving for liquid feed\u003c\/h3\u003e\n\u003cdiv class=\"drf-callout\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eGranulate dissolves more slowly\u003c\/span\u003e\n\u003cp\u003eThe granulate is fully water-soluble, but it dissolves more slowly than a fine grade. Stir well, or dissolve in warm water and leave to stand for a few minutes before topping up. For a foliar spray, dissolve completely and strain through fine mesh first to protect your sprayer.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eLiquid feed \/ fertigation — root drench\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 1–2g per litre of water  |  \u003cstrong\u003eFrequency:\u003c\/strong\u003e weekly to fortnightly during fruiting\/flowering\u003c\/div\u003e\n\u003cp\u003eDissolve, then apply at the base of the plant. Ideal for topping up potassium when demand peaks. Lower rate for maintenance, higher rate when plants are in full production.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eFoliar spray\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 5–10g per litre of water  |  \u003cstrong\u003eFrequency:\u003c\/strong\u003e every 2 weeks during fruiting\u003c\/div\u003e\n\u003cp\u003eApply to both leaf surfaces in early morning or late evening. Foliar potassium is absorbed quickly and can ease deficiency within days. Dissolve fully and strain before spraying.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003ch3\u003eStep-by-step\u003c\/h3\u003e\n\u003col class=\"drf-steps\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eIdentify your potassium need.\u003c\/strong\u003e Fruiting and flowering crops have the highest demand. Scorched leaf edges, poor fruit set and weaker disease resistance are classic deficiency signs.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMeasure the rate.\u003c\/strong\u003e Use the rates above as a starting guide — a level teaspoon of granulate is about 5g.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApply and water in.\u003c\/strong\u003e For soil, scatter evenly and water thoroughly. For liquid feeding, dissolve fully before applying. Watering in moves potassium into the root zone.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTime it to demand.\u003c\/strong\u003e Potassium demand peaks through flowering and fruit development. Start when the first flowers appear and carry on to harvest.\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cdiv class=\"drf-callout\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eWorks well combined with…\u003c\/span\u003e\n\u003cp\u003ePair with Dr Forest crop feeds — \u003cstrong\u003eTomato\u003c\/strong\u003e, \u003ca href=\"\/products\/organic-rose-fertiliser\"\u003eRose \u0026amp; Flower\u003c\/a\u003e and \u003ca href=\"\/products\/organic-fruit-vegetable-fertiliser\"\u003eFruit \u0026amp; Vegetable\u003c\/a\u003e — where extra potassium is wanted during peak fruiting. Combine with \u003cstrong\u003eSeaweed\u003c\/strong\u003e for biostimulant activity and \u003cstrong\u003eCal-Mag\u003c\/strong\u003e where calcium is also needed. Zero nitrogen means it won't disturb bloom-phase ratios.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-callout drf-callout-gold\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eFurther reading\u003c\/span\u003e\n\u003cp\u003eNew to potassium minerals? See our guide to \u003ca href=\"\/blogs\/the-dr-forest-blog\/what-is-polyhalite\"\u003epolyhalite\u003c\/a\u003e, a multi-nutrient potassium mineral, and \u003ca href=\"\/blogs\/the-dr-forest-blog\/why-are-my-tomato-leaves-turning-yellow\"\u003ewhy tomato leaves turn yellow\u003c\/a\u003e — often a potassium or magnesium signal.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-panel\" id=\"drf-sp-panel4\"\u003e\n\u003ch2\u003eFrequently asked questions about sulphate of potash\u003c\/h2\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq1\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq1\"\u003eWhat is the difference between sulphate of potash and muriate of potash?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eBoth deliver potassium, but the accompanying ion differs. Muriate of potash (potassium chloride) carries 47% chloride, which can accumulate in soil and damage sensitive crops. Sulphate of potash is almost chloride-free and adds 18% sulphur. For container growing, tunnel crops and chloride-sensitive plants like tomatoes, strawberries and potatoes, sulphate of potash is the safer, better-quality choice.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq2\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq2\"\u003eIs sulphate of potash suitable for organic growing?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eYes. This sulphate of potash is certified for use in organic production under Regulation (EC) 834\/2007 as a naturally mined crude mineral salt — no synthetic processing and no chemical additives. It's approved for use in organic growing systems. (In the EU and Northern Ireland the equivalent regulation is now (EU) 2018\/848.)\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq3\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq3\"\u003eWhen should I apply sulphate of potash?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003ePotassium demand peaks through flowering and fruiting — begin when the first flowers appear and continue to harvest. For lawns, apply in spring and autumn. For general soil maintenance, once or twice in the growing season. Leaf-edge scorching, poor fruit set or rising disease are deficiency signs that warrant an immediate application.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq4\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq4\"\u003eHow much sulphate of potash should I use?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eAs a guide: 1–2g per litre when mixing into compost, 2–6g per 10-litre pot as a top dressing every 4–6 weeks, 20–50g per m² on outdoor beds, and 20–35g per m² on lawns. A level teaspoon of granulate is roughly 5g. Start at the lower end and increase for heavy-fruiting crops.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq5\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq5\"\u003eCan I dissolve the granulate in water?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eYes. Potassium sulphate is water-soluble, though the granulate dissolves more slowly than a fine grade. Stir well, or dissolve in warm water and let it stand for a few minutes. For foliar spraying, dissolve completely and strain through fine mesh first to protect your sprayer. For most gardeners, applying to the soil and watering in is the simplest route.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq6\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq6\"\u003eWill it burn my plants?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eSulphate of potash has a low salt index compared with muriate of potash, so it's much less likely to scorch roots. Apply at the recommended rates, water in afterwards and keep granules off stems. At normal garden rates the risk is very low.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq7\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq7\"\u003eHow is sulphate of potash different from tomato feed?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eMost liquid tomato feeds are balanced NPK fertilisers with nitrogen, phosphorus and potassium together. Sulphate of potash is a \u003cem\u003esingle-nutrient supplement\u003c\/em\u003e — only potassium and sulphur. That makes it ideal for lifting potassium on its own, without adding nitrogen (which pushes leafy growth at the expense of fruit) or phosphorus.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq8\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq8\"\u003eWhat crops benefit most from sulphate of potash?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eAll fruiting and flowering crops: tomatoes, peppers, chillies, strawberries, raspberries, grapes, courgettes, cucumbers, roses, dahlias and sweet peas. Root crops like potatoes and carrots benefit too, since potassium improves starch and storage quality. Brassicas and alliums make particular use of the sulphur.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq9\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq9\"\u003eCan I use it alongside Dr Forest fertilisers?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eYes. It pairs naturally with any Dr Forest blend where extra potassium is wanted — usually at peak fruiting or flowering. With zero nitrogen and zero phosphorus, it won't disturb the NPK ratio of your base feed. Many growers run a crop-specific fertiliser as the base and add sulphate of potash as a targeted booster during heavy production.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-sp-faq10\" type=\"checkbox\"\u003e\u003clabel class=\"drf-faq-q\" for=\"drf-sp-faq10\"\u003eHow should I store sulphate of potash?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\n\u003cdiv\u003eKeep it cool and dry in the sealed bag. Potassium sulphate isn't hygroscopic under normal conditions, so it won't draw in moisture and clump if kept sealed. Stored properly, shelf life is effectively indefinite — it's a stable mineral salt.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e","brand":"Dr Forest","offers":[{"title":"500g","offer_id":53587298615670,"sku":"DF-SOP-500G","price":6.25,"currency_code":"GBP","in_stock":true},{"title":"1.5kg","offer_id":37684919992507,"sku":"DF-SOP-1.5","price":11.0,"currency_code":"GBP","in_stock":true},{"title":"4kg","offer_id":37684920025275,"sku":"DF-SOP-4","price":21.99,"currency_code":"GBP","in_stock":true},{"title":"9kg","offer_id":37684920090811,"sku":"DF-SOP-9","price":40.0,"currency_code":"GBP","in_stock":true},{"title":"15kg","offer_id":44740949409979,"sku":"DF-SOP-15","price":60.0,"currency_code":"GBP","in_stock":true},{"title":"36kg","offer_id":57119511740790,"sku":"DF-SOP-36","price":117.49,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0049\/8194\/8504\/files\/dr-forests-organic-sulphate-potash-fertiliser-50-fertiliser-pile-707.webp?v=1785512767","url":"https:\/\/www.drforest.co.uk\/products\/sulphate-of-potash","provider":"Dr Forest","version":"1.0","type":"link"}