{"product_id":"granulated-gypsum-clay-breaker","title":"Granulated Gypsum | Clay Breaker \u0026 Calcium Sulphur Feed","description":"\u003c!-- Dr Forest — Granulated Gypsum Product Page --\u003e\u003c!-- Prefix: drf-gg- (granulated gypsum) --\u003e\u003c!-- Design System v1.0 · 5-tab · Pure CSS, no JavaScript · Shopify-safe --\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-light:  #E8F0EB;\n    --drf-grn-mid:    #4a7a5e;\n    --drf-grn-dark:   #0F2A1F;\n    --drf-gold:       #C5A55A;\n    --drf-gold-light: #FAF7F0;\n    --drf-cream:      #F5F2EC;\n    --drf-white:      #FFFFFF;\n    --drf-border:     #d4cfc5;\n    --drf-muted:      #3A4A40;\n  }\n  .drf-wrap h2 { font-family: 'Cormorant Garamond', serif; 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margin-top: 0.25em; }\n\n  \/* ── TABS ── *\/\n  .drf-tabs-wrap { max-width: 100%; overflow: hidden; }\n  .drf-tabs-wrap input[type=\"radio\"] { display: none; }\n  .drf-tab-labels { display: flex; align-items: stretch; border-bottom: 2px solid var(--drf-border); margin-bottom: 1.2em; }\n  .drf-tab-labels label { flex: 1 1 0; padding: 0.75em 0.4em; font-size: 0.72em; font-weight: 600; letter-spacing: 0.04em; text-transform: uppercase; color: #8b6914; background: var(--drf-gold-light); cursor: pointer; text-align: center; display: flex; align-items: center; justify-content: center; border-bottom: 3px solid var(--drf-gold); margin-bottom: -2px; transition: all 0.15s; }\n  .drf-tab-labels label:hover { color: var(--drf-grn); background: var(--drf-grn-light); border-bottom-color: var(--drf-grn); }\n  .drf-panel { display: none; }\n  #drf-gg-tab1:checked ~ .drf-tab-labels label[for=\"drf-gg-tab1\"],\n  #drf-gg-tab2:checked ~ .drf-tab-labels label[for=\"drf-gg-tab2\"],\n  #drf-gg-tab3:checked ~ .drf-tab-labels label[for=\"drf-gg-tab3\"],\n  #drf-gg-tab4:checked ~ .drf-tab-labels label[for=\"drf-gg-tab4\"],\n  #drf-gg-tab5:checked ~ .drf-tab-labels label[for=\"drf-gg-tab5\"] { color: var(--drf-grn); background: var(--drf-grn-light); border-bottom-color: var(--drf-grn); font-weight: 700; }\n  #drf-gg-tab1:checked ~ .drf-panels #drf-gg-panel1,\n  #drf-gg-tab2:checked ~ .drf-panels #drf-gg-panel2,\n  #drf-gg-tab3:checked ~ .drf-panels #drf-gg-panel3,\n  #drf-gg-tab4:checked ~ .drf-panels #drf-gg-panel4,\n  #drf-gg-tab5:checked ~ .drf-panels #drf-gg-panel5 { 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); 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color: var(--drf-gold); line-height: 1; }\n  .drf-mech h4 { margin-top: 0.2em; color: var(--drf-grn); text-transform: none; letter-spacing: 0; font-size: 1em; }\n  .drf-mech p { font-size: 0.92em; color: var(--drf-muted); margin-bottom: 0; }\n\n  \/* ── RATE CARDS ── *\/\n  .drf-rate { border: 1px solid var(--drf-border); padding: 1em 1.2em; margin: 0.8em 0; background: var(--drf-grn-light); }\n  .drf-rate h4 { margin-top: 0; color: var(--drf-grn); text-transform: none; letter-spacing: 0; font-size: 1em; font-family: 'Cormorant Garamond', serif; border-bottom: 1px solid var(--drf-gold); padding-bottom: 0.5em; margin-bottom: 0.6em; }\n  .drf-rate-meta { font-size: 0.85em; color: var(--drf-muted); margin-bottom: 0.5em; }\n  .drf-rate-meta strong { color: var(--drf-gold); }\n  .drf-rate p { font-size: 0.92em; color: var(--drf-muted); margin-bottom: 0; }\n\n  \/* ── STEPS ── *\/\n  .drf-steps { counter-reset: drf-step; list-style: none; padding: 0; }\n  .drf-steps li { counter-increment: drf-step; 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color: var(--drf-grn); text-transform: none; letter-spacing: 0; font-size: 1.05em; font-family: 'Cormorant Garamond', serif; border-bottom: 1px solid var(--drf-gold); padding-bottom: 0.4em; margin-bottom: 0.6em; }\n\n  \/* ── TABLES ── *\/\n  .drf-wrap table { width: 100%; border-collapse: collapse; margin: 1.2em 0; font-size: 0.92em; }\n  .drf-wrap table th { background: var(--drf-grn); color: #fff; font-weight: 600; text-align: left; padding: 0.6em 0.8em; font-size: 0.85em; letter-spacing: 0.04em; }\n  .drf-wrap table td { padding: 0.55em 0.8em; border-bottom: 1px solid var(--drf-border); }\n  .drf-wrap table tr:nth-child(even) td { background: var(--drf-grn-light); }\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: 600; 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: 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); border-color: var(--drf-grn); color: #fff; }\n  .drf-faq input:checked ~ .drf-faq-a { max-height: 900px; }\n\n  \/* ── REFERENCES \u0026 RULE ── *\/\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 ol { padding-left: 1.4em; margin: 0; }\n  .drf-refs li { margin-bottom: 0.3em; }\n  .drf-sep { border: none; border-top: 1px solid var(--drf-gold); width: 200px; margin: 1.8em auto; }\n\u003c\/style\u003e\n\u003cdiv class=\"drf-wrap\"\u003e\n\u003cdiv class=\"drf-tabs-wrap\"\u003e\n\u003cinput checked id=\"drf-gg-tab1\" name=\"drf-gg-tabset\" type=\"radio\"\u003e \u003cinput id=\"drf-gg-tab2\" name=\"drf-gg-tabset\" type=\"radio\"\u003e \u003cinput id=\"drf-gg-tab3\" name=\"drf-gg-tabset\" type=\"radio\"\u003e \u003cinput id=\"drf-gg-tab4\" name=\"drf-gg-tabset\" type=\"radio\"\u003e \u003cinput id=\"drf-gg-tab5\" name=\"drf-gg-tabset\" type=\"radio\"\u003e\n\u003cdiv class=\"drf-tab-labels\"\u003e\n\u003clabel for=\"drf-gg-tab1\"\u003eOverview\u003c\/label\u003e \u003clabel for=\"drf-gg-tab2\"\u003eThe Science\u003c\/label\u003e \u003clabel for=\"drf-gg-tab3\"\u003eHow to Use\u003c\/label\u003e \u003clabel for=\"drf-gg-tab4\"\u003eRates by Crop\u003c\/label\u003e \u003clabel for=\"drf-gg-tab5\"\u003eFAQ\u003c\/label\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-panels\"\u003e\n\n\u003c!-- ══════════════ TAB 1 — OVERVIEW ══════════════ --\u003e\n\u003cdiv id=\"drf-gg-panel1\" class=\"drf-panel\"\u003e\n\n\u003cdiv class=\"drf-badge-row\"\u003e\n\u003cspan class=\"drf-badge drf-badge-green\"\u003e40% SO₃\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003e30% CaO\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003e3% MgO\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-green\"\u003e2–5mm Granule\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-gold\"\u003eNaturally Mined\u003c\/span\u003e \u003cspan class=\"drf-badge drf-badge-gold\"\u003eWon't Change Soil pH\u003c\/span\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eGranulated gypsum for clay soil, lawns and calcium-hungry crops\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eGranulated gypsum is a naturally mined mineral — calcium sulphate — screened into 2–5mm granules. It feeds plants calcium and sulphur, and it helps break up sticky clay, without changing your soil's pH.\u003c\/strong\u003e The calcium is what does the work on clay. It swaps places with the sodium clinging to the clay particles, and once that happens the particles stop smearing together and start clumping into crumbs. Crumbs are what let water drain away and roots push through.\u003c\/p\u003e\n\n\u003cp\u003eThe analysis is \u003cstrong\u003e40% SO₃, 30% CaO and 3% MgO\u003c\/strong\u003e plus trace elements. In plain numbers that is \u003cstrong\u003e16% sulphur, 21% calcium and just under 2% magnesium\u003c\/strong\u003e. Magnesium is unusual in a gypsum, so a single granule covers all three of the nutrients that sit just behind N-P-K in importance. This is mined rock, not the gypsum recovered from power station chimneys or recycled out of old plasterboard. The granules spread to \u003cstrong\u003e36 metres\u003c\/strong\u003e from a tractor spreader and do not blow about the way a powder does.\u003c\/p\u003e\n\n\u003cdiv class=\"drf-stats\"\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e40%\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eSulphur (SO₃)\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e30%\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eCalcium (CaO)\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e3%\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eMagnesium (MgO)\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e2–5mm\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eGranule Size\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003e36m\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eMax Spread Width\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-stat\"\u003e\n\u003cspan class=\"drf-stat-number\"\u003eZero\u003c\/span\u003e\u003cspan class=\"drf-stat-label\"\u003eChange To Soil pH\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cp\u003eWorth knowing: the national fertiliser guide British farmers work from (RB209, published by the AHDB) lists quarried gypsum at 40% SO₃. This sits exactly on the figure British growers already use to work out how much sulphur to put on, so the rates further down translate straight across.\u003c\/p\u003e\n\n\u003ch3\u003eWhat it does\u003c\/h3\u003e\n\n\u003cul class=\"drf-uses\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eLoosens sticky clay.\u003c\/strong\u003e Calcium pushes sodium off the surface of the clay particles, and they clump into crumbs instead of slumping into an airless pan.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFeeds sulphur in the form roots can use immediately.\u003c\/strong\u003e Plants take sulphur up as sulphate, and that is exactly what gypsum is. Yellow powdered sulphur has to be converted by soil bacteria first, which stalls in cold or dry ground.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAdds calcium without liming.\u003c\/strong\u003e Lime and shell meal both make soil more alkaline. Gypsum does not, so it is one of the few ways to feed calcium to soil that is already where you want it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eKeeps phosphorus out of ditches and ponds.\u003c\/strong\u003e In American field trials, two annual applications cut the phosphorus washing off the surface by around 40%.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStops the surface crusting over.\u003c\/strong\u003e The hard cap that forms after heavy rain is what traps seedlings underground. Gypsum keeps the top centimetre crumbly enough for them to get through.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAdds magnesium as well.\u003c\/strong\u003e 3% MgO, which most agricultural gypsums do not carry at all.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003chr class=\"drf-sep\"\u003e\n\n\u003ch3\u003eGranulated, micronised or liquid?\u003c\/h3\u003e\n\n\u003cdiv class=\"drf-compare\"\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eGranulated gypsum (this product)\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003e2–5mm granule, spread-tested to 36m from a tractor-mounted broadcast spreader, with none of the dust of a powder\u003c\/li\u003e\n\u003cli\u003eBest for whole lawns, beds, allotments, paddocks and field-scale work\u003c\/li\u003e\n\u003cli\u003eDissolves progressively with rainfall rather than all at once\u003c\/li\u003e\n\u003cli\u003eHandles and stores like any granular fertiliser, and mixes straight in with your other dry feeds in the spreader\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eMicronised gypsum powder\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eDissolves faster, because ground-up powder has far more surface touching the soil\u003c\/li\u003e\n\u003cli\u003eBetter for potting mixes, small containers and precise dosing by the gram\u003c\/li\u003e\n\u003cli\u003eDusty in wind; awkward to spread evenly over a large area\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eLiquid gypsum\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eA ready-mixed liquid you put on through a watering can or sprayer\u003c\/li\u003e\n\u003cli\u003eFastest to act; useful for spot-treating a patch or an established lawn you don't want to walk a spreader over\u003c\/li\u003e\n\u003cli\u003eCarries far less material per pound spent, so a poor choice when you need tonnage on the ground\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-callout drf-callout-gold\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eRead this before you buy\u003c\/span\u003e\n\u003cp\u003eWorth being straight about this: gypsum does not work on every clay. It works where the clay has gone \u003cem\u003eslumped\u003c\/em\u003e — where sodium has pushed the calcium off the particles and the soil has collapsed into a greasy mud that sets hard. Plenty of British clay is simply heavy rather than slumped, and on that sort of ground gypsum does far less. The RHS puts it carefully: \u003cem\u003e\"Some, but not all, clay soils respond to extra calcium.\"\u003c\/em\u003e Our advice is theirs — do a marked patch first and look at it after a winter. A quick test: if your soil crumbles when you squeeze a moist handful, it is not slumped, and compost will do more for it than gypsum.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cp\u003eBagged and dispatched from Stockport, Greater Manchester. A mined mineral, carrying no animal by-products — here or anywhere else in the Dr Forest range. Safe around children, pets, bees and wildlife once watered in.\u003c\/p\u003e\n\n\u003c\/div\u003e\n\n\u003c!-- ══════════════ TAB 2 — THE SCIENCE ══════════════ --\u003e\n\u003cdiv id=\"drf-gg-panel2\" class=\"drf-panel\"\u003e\n\n\u003ch2\u003eThe science\u003c\/h2\u003e\n\n\u003cp\u003eGypsum is one of the better-studied soil amendments and one of the most oversold. Here is what the evidence actually shows, and where it runs out. If you only want to know how much to put down, skip to the next two tabs.\u003c\/p\u003e\n\n\u003ch3\u003eWhat is actually in it\u003c\/h3\u003e\n\n\u003cp\u003eCalcium sulphate comes in two forms: one with water locked into the crystal, one without. The chemistry puts a hard ceiling on how much calcium and sulphur any gypsum can possibly contain, which makes the table below a useful lie-detector for label claims.\u003c\/p\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003e\u003c\/th\u003e\n\u003cth\u003eAnhydrite (no water)\u003c\/th\u003e\n\u003cth\u003eGypsum (water in the crystal)\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCalcium (Ca)\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e29.44%\u003c\/td\u003e\n\u003ctd\u003e23.28%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eSulphur (S)\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e23.55%\u003c\/td\u003e\n\u003ctd\u003e18.62%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eas SO₃\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e58.81%\u003c\/td\u003e\n\u003ctd\u003e46.50%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eas CaO\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e41.19%\u003c\/td\u003e\n\u003ctd\u003e32.57%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eWater locked in the crystal\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e0%\u003c\/td\u003e\n\u003ctd\u003e20.93%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cp\u003eSo any product claiming more than 29.44% calcium or 58.81% SO₃ is either measuring it a different way, printing CaO where it means Ca, or is not what it says on the bag. To convert between the two ways of writing it: sulphur × 2.5 gives SO₃, and calcium × 1.4 gives CaO.\u003c\/p\u003e\n\n\u003cp\u003eGypsum dissolves at about 2.5 grams per litre of water, roughly 200 times more readily than ground limestone. That is why it acts in weeks rather than years. A 2–5mm granule has far less surface touching the soil than a powder, so it releases more slowly and keeps going for longer.\u003c\/p\u003e\n\n\u003ch3\u003eWhy it will not change your pH\u003c\/h3\u003e\n\n\u003cp\u003eLime raises pH because the carbonate in it mops up acid. Gypsum contains no carbonate at all — it splits into calcium and sulphate, and sulphate cannot mop up anything. So the calcium gets on with its job while the pH stays exactly where it was. The trade term for this is a neutralising value of zero, and it is the single most useful thing about gypsum.\u003c\/p\u003e\n\n\u003cp\u003eThe field data agree. Chaganti and colleagues found no pH change at either rate they tested (\u003cem\u003eAgronomy Journal\u003c\/em\u003e, 2019). Anderson and colleagues found no pH rise on acid Australian soils (\u003cem\u003eAgronomy\u003c\/em\u003e, 2021). Where any shift shows up at all it is slightly \u003cem\u003edownward\u003c\/em\u003e, a tenth to three tenths of a point. That is why gypsum is the calcium you reach for on blueberries, rhododendrons and camellias — anything where you have spent years getting the soil acid and would rather not undo it.\u003c\/p\u003e\n\n\u003cdiv class=\"drf-pullquote\"\u003eGypsum is not lime. It will not raise your pH, and it is not a substitute for anything that does.\u003c\/div\u003e\n\n\u003ch3\u003eHow calcium unsticks clay\u003c\/h3\u003e\n\n\u003cp\u003eClay particles are microscopic flat plates with a negative charge on the surface, and something has to balance that charge. What balances it makes all the difference. Sodium holds the plates apart, so they slide over each other like wet playing cards — that is the greasy, structureless mud that dries into a pan you could pave a drive with. Calcium has twice the charge in a smaller package, and it lets the plates pull together into crumbs. Crumbs stack up, and the gaps between them are the drainage, the air and the room for roots.\u003c\/p\u003e\n\n\u003cp\u003eThere is a second half to it, and it is the part most explanations leave out. Quirk and Schofield showed back in 1955 that soil stops draining once the water sitting in it becomes too \u003cem\u003epure\u003c\/em\u003e — clean rainwater falling on a sodium-heavy clay is the worst case there is. Gypsum dissolving into that water fixes the problem straight away, holding the structure together while the slower calcium-for-sodium swap gets on with the real work. The more sodium a soil is carrying, the more dissolved calcium it needs: roughly nine times more on badly affected ground than on clean ground.\u003c\/p\u003e\n\n\u003ch4\u003eResearch findings\u003c\/h4\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e01\u003c\/span\u003e\n\u003ch4\u003eRain soaked in twice as fast\u003c\/h4\u003e\n\u003cp\u003eOn soils prone to crusting, gypsum at 5 tonnes per hectare under simulated heavy rain roughly doubled the rate water soaked in, and cut the amount of soil washed off the surface by 30–50%. Miller, \u003cem\u003eSoil Science Society of America Journal\u003c\/em\u003e 51:1314–1320, 1987. The trial used phosphogypsum, an industrial by-product that dissolves faster than mined rock, so expect the same effect from mined gypsum spread over a longer period (Keren and Shainberg, 1981).\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e02\u003c\/span\u003e\n\u003ch4\u003eLooser soil, water reaching deeper\u003c\/h4\u003e\n\u003cp\u003eThe soil went from tightly packed to noticeably looser, water penetrated 27cm instead of 17cm, and it kept soaking in for 158 minutes instead of 102. Air space in the soil rose by 3.7%. Luo et al., \u003cem\u003eAgronomy\u003c\/em\u003e 15:35, 2025. Read with the caveat attached: this was phosphogypsum on a Chinese salt-affected soil, and you should not assume it carries straight across to a British garden.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e03\u003c\/span\u003e\n\u003ch4\u003eStill working twenty-six years later\u003c\/h4\u003e\n\u003cp\u003eOne application, measured again more than a quarter of a century on: sodium was still down, most noticeably between 25cm and a metre deep, and calcium had worked its way to 1.25 metres. Gypsum is slow, but it is not temporary. Green et al., \u003cem\u003eSoil and Tillage Research\u003c\/em\u003e 233:105780, 2023.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e04\u003c\/span\u003e\n\u003ch4\u003eCrumb structure survived the frosts\u003c\/h4\u003e\n\u003cp\u003eFreezing and thawing is what smashes soil crumbs apart over a British winter. Calcium sulphate at just 0.2% by weight kept crumbs measurably more stable through freeze–thaw across six different soils. Lime, tested alongside, made almost no difference. Lehrsch, Sojka \u0026amp; Jolley, \u003cem\u003eCATENA Supplement\u003c\/em\u003e 24:115–127, 1993.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e05\u003c\/span\u003e\n\u003ch4\u003ePhosphorus stayed in the field instead of the stream\u003c\/h4\u003e\n\u003cp\u003eOn ground testing very high for phosphorus, two annual applications at 2.24 tonnes per hectare cut the phosphorus washing off the surface by about 40%. King, Williams, Dick \u0026amp; LaBarge, \u003cem\u003eJournal of Environmental Quality\u003c\/em\u003e 45:1722–1730, 2016. This trial used gypsum recovered from power station flue gas rather than mined rock.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e06\u003c\/span\u003e\n\u003ch4\u003eThe same result on clay, in a wet climate\u003c\/h4\u003e\n\u003cp\u003eFinland is the closest published match to British conditions — clay soil, plenty of rain. Gypsum at 4 tonnes per hectare across 91% of the farmland in a small river catchment cut phosphorus washing off the land by 57–64%, depending on which analysis you read, and the benefit ran four to five years. Ekholm et al., \u003cem\u003eAgricultural and Food Science\u003c\/em\u003e 21(3), 2012.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e07\u003c\/span\u003e\n\u003ch4\u003eA quarter more cauliflower\u003c\/h4\u003e\n\u003cp\u003eGypsum at 4 tonnes per hectare raised cauliflower yield by 25%, and sulphur treatments raised broccoli by up to 14%. The same trial recorded a small downward pH shift under gypsum, and an upward one under lime. \u003cem\u003eActa Horticulturae\u003c\/em\u003e 627:22.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-mech\"\u003e\n\u003cspan class=\"drf-mech-num\"\u003e08\u003c\/span\u003e\n\u003ch4\u003eThe sulphur reached the plants, quickly\u003c\/h4\u003e\n\u003cp\u003eSulphur in the soil rose three- to eightfold after gypsum, and the sulphur measured in the leaves of the crop rose between 15% and 97% depending on the site. Chaganti, Culman, Dick \u0026amp; Kost, \u003cem\u003eAgronomy Journal\u003c\/em\u003e 111:1109–1117, 2019.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003chr class=\"drf-sep\"\u003e\n\n\u003ch3\u003eWhy British soils ran out of sulphur\u003c\/h3\u003e\n\n\u003cp\u003eFor most of the industrial era, British crops were fertilised with sulphur by accident. Coal smoke put it there. Then the Clean Air Acts cleaned up the smoke, power stations were fitted with scrubbers, and coal generation ended altogether. The free sulphur went with it, and nobody replaced it.\u003c\/p\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eMeasure\u003c\/th\u003e\n\u003cth\u003eFigure\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eUK SO₂ emissions, 1990\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e3,744 kilotonnes\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eUK SO₂ emissions, 2024\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e84 kilotonnes — the lowest on record, a 98% fall\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePhasing of the decline\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e−9% 1970–1991 · −83% 1991–2005 · −99% 2005–2022\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eSulphur deposited on farmland, 1996\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e5–25 kg S\/ha\/yr\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eProjected by 2010\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e5–10 kg S\/ha\/yr\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePlant-available soil S worldwide, 2000–2020\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eDown 34–86%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cp\u003eSulphur is what plants build protein with, and it is the element behind flavour in a whole category of crops. The compounds that make cabbage taste of cabbage, mustard taste hot and an onion make you cry are all sulphur compounds. A plant short of sulphur cannot use its nitrogen properly either, so the nitrogen you paid for washes away instead of going into growth.\u003c\/p\u003e\n\n\u003cp\u003eBritish trial data are specific about this. The levy board that funds farming research monitored four crops across England and Wales and found worthwhile yield increases from sulphur in \u003cstrong\u003e32% of oilseed rape trials, 15% of spring barley, 13% of winter barley and 10% of winter wheat\u003c\/strong\u003e. Light, sandy ground responded more than twice as often as heavy ground did. The biggest single result was an \u003cstrong\u003e81% yield increase\u003c\/strong\u003e in oilseed rape on light soil.\u003c\/p\u003e\n\n\u003cp\u003eRothamsted's work on malting barley found worthwhile responses in five trials out of eight. The sites that responded had markedly less sulphur in the soil than the ones that did not, and a simple lab test — the ratio of nitrogen to sulphur in the grain — told the two groups apart every time. That test is still the most reliable way to know whether you have a problem.\u003c\/p\u003e\n\n\u003cdiv class=\"drf-callout\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eDiagnosing sulphur shortage\u003c\/span\u003e\n\u003cp\u003eLook at which leaves are going yellow. Sulphur shortage shows on the \u003cem\u003eyoungest\u003c\/em\u003e growth; nitrogen shortage shows on the oldest. The reason is simple: a plant can pull nitrogen back out of its old leaves to feed new growth, but it cannot do that with sulphur, so the newest leaves are the ones that go pale. A leaf analysis measuring the nitrogen-to-sulphur ratio will confirm it if you want certainty.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003chr class=\"drf-sep\"\u003e\n\n\u003ch3\u003eWhere gypsum does not help\u003c\/h3\u003e\n\n\u003cp\u003eA page that only lists benefits will disappoint somebody. Here is where gypsum genuinely does not deliver, and the evidence is solid on all of it.\u003c\/p\u003e\n\n\u003cdiv class=\"drf-compare\"\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eIt does not fix compaction\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eGypsum changes soil chemistry, not soil physics. In American trials on ordinary soil it made no measurable difference to how hard the ground was to push a probe through.\u003c\/li\u003e\n\u003cli\u003eCompaction from machinery, footfall or waterlogging needs aeration, deep-rooting cover crops or a fork.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eIt does not reliably fix blossom end rot\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eIt is a watering problem far more than a calcium problem. Calcium only travels around a plant in the water the roots draw up, and when a fruit is swelling fastest the plant sends that water to the leaves first. The end of the fruit runs short no matter how much calcium is sitting in the soil.\u003c\/li\u003e\n\u003cli\u003eUC Cooperative Extension: \u003cem\u003e\"Adding calcium to the soil rarely alleviates the problem\"\u003c\/em\u003e and \u003cem\u003e\"blossom-end rot is primarily a water issue.\"\u003c\/em\u003e Consistent watering does more than any amendment.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eIt does not work on carrot cavity spot\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eCavity spot is caused by \u003cem\u003ePythium\u003c\/em\u003e, a soil-borne mould. The AHDB's own guidance states plainly that gypsum will not reduce it. Lime does help, cutting it by a quarter to a half, but that works by shifting the pH rather than by adding calcium.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eIt does not correct bitter pit in apples by itself\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eTorres and colleagues (\u003cem\u003eFrontiers in Plant Science\u003c\/em\u003e 15:1383645, 2024) conclude that the calcium shortage in a bitter-pitted apple \u003cem\u003e\"is minimally corrected through improved Ca fertilization\"\u003c\/em\u003e — put plainly, adding calcium to the soil barely touches it. The balance between potassium, magnesium and calcium inside the fruit predicts bitter pit better than the amount of calcium does.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"drf-compare-box\"\u003e\n\u003ch4\u003eIt will not \"balance\" your soil\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eThe idea that soil needs a fixed ratio of calcium to magnesium to potassium — sold as cation balancing, or the Albrecht method — has not survived testing. Kopittke and Menzies (\u003cem\u003eSoil Science Society of America Journal\u003c\/em\u003e 71:259–265, 2007) found soil fertility cannot be pinned to nutrient ratios at all, and that the original experiments failed to allow for pH.\u003c\/li\u003e\n\u003cli\u003eYields were unaffected across calcium-to-magnesium ratios running from 0.25:1 all the way to 31:1. Within any sensible range, the ratio simply does not matter.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-callout-dark\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eMore is not better\u003c\/span\u003e\n\u003cp\u003eAt 20 tonnes per hectare — roughly ten times any garden rate — gypsum halved earthworm numbers and cut their total weight by two thirds over five months (Chen et al., \u003cem\u003eJournal of Environmental Quality\u003c\/em\u003e 43:263–272, 2014). Heavy rates on soil that is not acid can also strip out potassium and magnesium, because the sulphate pairs up with magnesium and washes it away as Epsom salt. Stay inside the rates on the next tab and none of this applies.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-refs\"\u003e\n\u003ch4\u003eReferences\u003c\/h4\u003e\n\u003col\u003e\n\u003cli\u003eQuirk, J.P. \u0026amp; Schofield, R.K. (1955) The effect of electrolyte concentration on soil permeability. \u003cem\u003eJournal of Soil Science\u003c\/em\u003e 6:163–178.\u003c\/li\u003e\n\u003cli\u003eMiller, W.P. (1987) Infiltration and soil loss of three gypsum-amended Ultisols under simulated rainfall. \u003cem\u003eSoil Science Society of America Journal\u003c\/em\u003e 51(5):1314–1320.\u003c\/li\u003e\n\u003cli\u003eLehrsch, G.A., Sojka, R.E. \u0026amp; Jolley, P.M. (1993) Freezing effects on aggregate stability of soils amended with lime and gypsum. \u003cem\u003eCATENA Supplement\u003c\/em\u003e 24:115–127.\u003c\/li\u003e\n\u003cli\u003eKeren, R. \u0026amp; Shainberg, I. (1981) Effect of dissolution rate on the efficiency of industrial and mined gypsum in improving infiltration of a sodic soil. \u003cem\u003eSoil Science Society of America Journal\u003c\/em\u003e 45.\u003c\/li\u003e\n\u003cli\u003eOster, J.D. (1982) Gypsum usage in irrigated agriculture: a review. \u003cem\u003eFertilizer Research\u003c\/em\u003e 3(1):73–89.\u003c\/li\u003e\n\u003cli\u003eCampbell, G.W. \u0026amp; Smith, R.I. (1996) Spatial and temporal trends in atmospheric sulphur deposition to agricultural surfaces in the United Kingdom. \u003cem\u003eInternational Fertiliser Society\u003c\/em\u003e Proceeding 378.\u003c\/li\u003e\n\u003cli\u003eKopittke, P.M. \u0026amp; Menzies, N.W. (2007) A review of the use of the basic cation saturation ratio and the \"ideal\" soil. \u003cem\u003eSoil Science Society of America Journal\u003c\/em\u003e 71:259–265.\u003c\/li\u003e\n\u003cli\u003eChen, L., Kost, D., Tian, Y. et al. (2014) Effects of gypsum on trace metals in soils and earthworms. \u003cem\u003eJournal of Environmental Quality\u003c\/em\u003e 43:263–272.\u003c\/li\u003e\n\u003cli\u003eKing, K.W., Williams, M.R., Dick, W.A. \u0026amp; LaBarge, G.A. (2016) Decreasing phosphorus loss in tile-drained landscapes using flue gas desulfurization gypsum. \u003cem\u003eJournal of Environmental Quality\u003c\/em\u003e 45(5):1722–1730.\u003c\/li\u003e\n\u003cli\u003eEkholm, P. et al. (2012) Gypsum amendment of soils reduces phosphorus losses in an agricultural catchment. \u003cem\u003eAgricultural and Food Science\u003c\/em\u003e 21(3).\u003c\/li\u003e\n\u003cli\u003eChaganti, V.N., Culman, S.W., Dick, W.A. \u0026amp; Kost, D. (2019) \u003cem\u003eAgronomy Journal\u003c\/em\u003e 111(3):1109–1117. DOI 10.2134\/agronj2018.10.0683.\u003c\/li\u003e\n\u003cli\u003eAnderson, G.C., Pathan, S., Hall, D.J.M. et al. (2021) \u003cem\u003eAgronomy\u003c\/em\u003e 11(5):826. DOI 10.3390\/agronomy11050826.\u003c\/li\u003e\n\u003cli\u003eGreen, H., Larsen, P., Koci, J. et al. (2023) Long-term effects of gypsum on the chemistry of sodic soils. \u003cem\u003eSoil and Tillage Research\u003c\/em\u003e 233:105780.\u003c\/li\u003e\n\u003cli\u003eTorres, E., Kalcsits, L. \u0026amp; Nieto, L.G. (2024) Is calcium deficiency the real cause of bitter pit? A review. \u003cem\u003eFrontiers in Plant Science\u003c\/em\u003e 15:1383645.\u003c\/li\u003e\n\u003cli\u003eLuo, A., Li, J., Xiao, Y., He, Z. \u0026amp; Liang, J. (2025) \u003cem\u003eAgronomy\u003c\/em\u003e 15:35. DOI 10.3390\/agronomy15010035.\u003c\/li\u003e\n\u003cli\u003eChen, L. \u0026amp; Dick, W.A. (2011) \u003cem\u003eGypsum as an Agricultural Amendment: General Use Guidelines.\u003c\/em\u003e Ohio State University Extension Bulletin 945.\u003c\/li\u003e\n\u003cli\u003eAHDB, \u003cem\u003eNutrient Management Guide (RB209)\u003c\/em\u003e, Sections 3–7, 2020–2023 editions.\u003c\/li\u003e\n\u003cli\u003eDefra (2026) \u003cem\u003eEmissions of air pollutants in the UK — Sulphur dioxide.\u003c\/em\u003e\n\u003c\/li\u003e\n\u003cli\u003eAHDB projects PR374 (Carver) and PR369 (Zhao, Rothamsted Research), sulphur monitoring and malting barley.\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n\n\u003c!-- ══════════════ TAB 3 — HOW TO USE ══════════════ --\u003e\n\u003cdiv id=\"drf-gg-panel3\" class=\"drf-panel\"\u003e\n\n\u003ch2\u003eHow to use granulated gypsum\u003c\/h2\u003e\n\n\u003cdiv class=\"drf-callout drf-callout-gold\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eMeasuring and coverage\u003c\/span\u003e\n\u003cp\u003eA rounded tablespoon holds roughly 20g of granules and a standard 250ml cup roughly 300g. At the general soil-conditioning rate of 200 g\/m², a 1.5kg bag covers about 7.5 m², 4kg covers 20 m², 9kg covers 45 m², 15kg covers 75 m² and 30kg covers 150 m². At the 50 g\/m² lawn maintenance rate those same bags cover 30, 80, 180, 300 and 600 m². On a lawn there is no need to rake them in; they work their way down through the grass on their own.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch3\u003eTwo very different jobs, two very different rates\u003c\/h3\u003e\n\n\u003cp\u003eThis trips people up, so it is worth being blunt about it. Gypsum is used at one order of magnitude to \u003cem\u003efeed\u003c\/em\u003e a crop sulphur and calcium, and at another to \u003cem\u003echange the structure\u003c\/em\u003e of a soil.\u003c\/p\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003ePurpose\u003c\/th\u003e\n\u003cth\u003eProduct rate\u003c\/th\u003e\n\u003cth\u003eDelivers\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cstrong\u003eSulphur nutrition\u003c\/strong\u003e (most vegetables, potatoes, peas)\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003e25 kg SO₃\/ha\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cstrong\u003eSulphur nutrition\u003c\/strong\u003e (vegetable brassicas, oilseed rape)\u003c\/td\u003e\n\u003ctd\u003e12.5–18.8 g\/m², up to 20 g\/m² for oilseed rape\u003c\/td\u003e\n\u003ctd\u003e50–80 kg SO₃\/ha\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eLawn maintenance\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e50–100 g\/m²\u003c\/td\u003e\n\u003ctd\u003e0.5–1 t\/ha\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eGeneral soil conditioning\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e200 g\/m²\u003c\/td\u003e\n\u003ctd\u003e2 t\/ha\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eHeavy clay improvement\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e400–600 g\/m²\u003c\/td\u003e\n\u003ctd\u003e4–6 t\/ha\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDigging into a new lawn or bed before planting\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e500 g\/m²\u003c\/td\u003e\n\u003ctd\u003e5 t\/ha\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cp\u003eIf you apply 200 g\/m² for structure, you have also applied 800 kg SO₃\/ha — vastly more sulphur than any crop needs in a season. That is fine as a one-off, because the surplus simply washes through over the winter. It is not fine every year on the same ground.\u003c\/p\u003e\n\n\u003chr class=\"drf-sep\"\u003e\n\n\u003ch3\u003eDirections by application\u003c\/h3\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eNew beds and borders\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 200 g\/m² | \u003cstrong\u003eTiming:\u003c\/strong\u003e Autumn or early spring, before planting | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Once, then review after a winter\u003c\/div\u003e\n\u003cp\u003eBroadcast evenly over the cleared bed and fork into the top 5cm. Water in, or apply before rain is forecast. On very heavy or previously waterlogged ground go to 400 g\/m². Leave a month before re-working the soil, and try a marked test patch alongside an untreated strip so you can see whether your particular clay is responding.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eHeavy clay improvement\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 400 g\/m², rising to 600 g\/m² on very heavy clay | \u003cstrong\u003eTiming:\u003c\/strong\u003e Autumn after rough digging | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Annually for up to three years, then assess\u003c\/div\u003e\n\u003cp\u003ePublished UK granular gypsum guidance for clay soils. Spread and incorporate to 10cm where you can; where you cannot dig, apply to the surface and let winter rain carry it down. Expect softer soil within twelve months and the full effect over two to three seasons. Pair with generous compost — organic matter improves clay unconditionally, gypsum only conditionally.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eEstablished lawns\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 50–100 g\/m² | \u003cstrong\u003eTiming:\u003c\/strong\u003e Spring and autumn | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Once or twice a year\u003c\/div\u003e\n\u003cp\u003eUse a walk-behind spreader set to the right rate, ideally just before rain. Drop spreaders lay a neater stripe; the spinning sort covers ground faster but drifts on a dry windy day. If rain does not turn up within a couple of days, water it in. Ordinary lawns can be done any time the ground is not frozen or sitting under water. Fine, closely-mown turf is happiest treated between late winter and early summer.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eCompacted, waterlogged or slow-draining turf\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 200 g\/m² after aeration, or 100–400 g\/m² brushed into tine holes | \u003cstrong\u003eTiming:\u003c\/strong\u003e Autumn, immediately after spiking or hollow-tining | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Up to twice a year where compaction is severe\u003c\/div\u003e\n\u003cp\u003eThe holes are the whole point — they get the gypsum down where the roots are instead of leaving it sitting on the thatch. Hollow-tine first, sweep up the cores, spread the granules and brush them into the holes with a stiff broom or a drag mat. Be clear about what is doing what: the aeration relieves the compaction, and the calcium then helps the new air spaces survive rather than closing straight back up. On soil that was never slumped in the first place, trials found no measurable change in how compacted it was.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eNew lawns, before seeding or turfing\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 500 g\/m², incorporated | \u003cstrong\u003eTiming:\u003c\/strong\u003e While you are preparing the ground | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Once\u003c\/div\u003e\n\u003cp\u003eThis is the one chance you will ever get to work calcium right through the depth of the soil instead of waiting years for rain to carry it down. Rotavate or fork into the top 10–15cm, level, firm, water thoroughly and leave it a week before seeding. On heavy clay it is worth the extra afternoon.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eVegetable plots and allotments\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 6–20 g\/m² for nutrition, or 200 g\/m² for structure | \u003cstrong\u003eTiming:\u003c\/strong\u003e At or soon after planting for nutrition; autumn for structure | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Annually\u003c\/div\u003e\n\u003cp\u003eTwo jobs, two very different rates — see the table above, and the crop-by-crop list on the next tab. If you are not chasing a specific problem and just want a sensible default, 20 g\/m² raked in at planting covers the sulphur needs of almost everything on a plot and adds useful calcium with it.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eContainers, raised beds and potting mixes\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e about 1g per litre of compost | \u003cstrong\u003eTiming:\u003c\/strong\u003e When mixing | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Each fresh batch\u003c\/div\u003e\n\u003cp\u003eRoughly 60g in a 60-litre bag of compost, or 600g to 1.2kg per cubic metre. Peat-free and coir composts are often short of calcium, and gypsum is one of the few ways to top it up without pushing the pH up too. Mix it through while the compost is still dry. For raised beds, use the bed rates above instead — the per-litre rate is for containers.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eSalt damage — de-icing spray, pet spots, coastal flooding\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 122–244 g\/m² on well-drained ground | \u003cstrong\u003eTiming:\u003c\/strong\u003e As soon as the soil has dried enough to walk on | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Single application, repeat the following season if needed\u003c\/div\u003e\n\u003cp\u003eThis is gypsum doing the thing it is genuinely best at — swapping calcium in for salt so the salt can be washed out. Spread it, then water heavily or wait for a proper spell of rain to carry the salt down and away. For ground flooded with seawater, UK guidance is a single dose of 500 g\/m² once it has dried out. One caveat worth taking seriously: on ground that drains badly, gypsum without enough water to flush it through can leave roots drier than before, not wetter.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eCompost heaps\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e around 450g per barrow load, or 20 kg per tonne of dry matter | \u003cstrong\u003eTiming:\u003c\/strong\u003e As you build the heap | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Each new heap\u003c\/div\u003e\n\u003cp\u003eThat sharp ammonia smell off a hot heap is nitrogen escaping into the air. Gypsum grabs it and holds it in the heap as a plant food instead. Trial work on dairy manure halved the nitrogen lost this way. It also firms up the greasy, slumped texture heaps get when they are too wet. This is for an open heap you turn, with air moving through it. Never add gypsum to a sealed or waterlogged manure or slurry store — see the warning below.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-rate\"\u003e\n\u003ch4\u003eClearing a muddy pond\u003c\/h4\u003e\n\u003cdiv class=\"drf-rate-meta\"\u003e\n\u003cstrong\u003eRate:\u003c\/strong\u003e 146–336 g\/m² of pond surface | \u003cstrong\u003eTiming:\u003c\/strong\u003e Autumn works best | \u003cstrong\u003eFrequency:\u003c\/strong\u003e Once; repeat if runoff re-muddies the water\u003c\/div\u003e\n\u003cp\u003eMuddy pond water is clay hanging in suspension — the same problem as slumped soil, and calcium settles it the same way, by clumping the particles until they are heavy enough to sink. Published rates vary depending on whether they are measured by surface area or by volume of water, so the sensible approach is to start at the low end and give it a few days before adding more. Mix it into a slurry with pond water and spread it about rather than tipping dry granules in one spot. It does not kill fish, does not change the water's pH and does not harm livestock drinking from it.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003chr class=\"drf-sep\"\u003e\n\n\u003ch3\u003eApplying it, step by step\u003c\/h3\u003e\n\n\u003col class=\"drf-steps\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eWork out which job you are doing.\u003c\/strong\u003e Feeding sulphur and calcium, or changing soil structure? The rates differ by a factor of ten to thirty. Weigh out for the area rather than eyeballing it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest a patch first on clay.\u003c\/strong\u003e Mark out a few square metres, treat it at 400 g\/m², leave an untreated strip beside it and compare them after a winter. Some clays respond dramatically and some barely at all, and no soil test predicts which reliably.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSpread evenly.\u003c\/strong\u003e Broadcast or drop spreader for anything over a few square metres; by hand in two passes at right angles for small beds. The 2–5mm granule throws to 36 metres, so halve your spreader setting and do two overlapping passes rather than one heavy one.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIncorporate where you can.\u003c\/strong\u003e Fork or rotavate into the top 5–10cm on bare ground. Rates above 250 g\/m² work considerably better incorporated than left on the surface. On established turf, leave it on top and let rain do the work.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWater it in.\u003c\/strong\u003e Granules need moisture to start dissolving. Roughly 25mm of rainfall dissolves about 53 g\/m² of gypsum, so a heavy autumn will work through a 200 g\/m² dressing over a season. Apply before rain if you can and save yourself the hose.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGive it time, then look again.\u003c\/strong\u003e Sulphur and calcium are available within weeks. Structural change takes longer — expect softer soil inside twelve months and the full benefit over two to three years.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003cdiv class=\"drf-callout-dark\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eOne thing never to do\u003c\/span\u003e\n\u003cp\u003e\u003cstrong\u003eNever mix gypsum into stored manure or slurry.\u003c\/strong\u003e Under anaerobic conditions the sulphate can be reduced to hydrogen sulphide, a genuinely dangerous gas. Spreading gypsum onto ground \u003cem\u003eafter\u003c\/em\u003e manure has been applied is fine and is a recognised conservation practice, and so is adding it to an open, turned compost heap. The hazard is specific to sealed or waterlogged stores where air cannot get in.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch3\u003eWhat it goes with\u003c\/h3\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eCombination\u003c\/th\u003e\n\u003cth\u003eVerdict\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eGarden lime\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eCompatible, and often complementary — lime lifts pH, gypsum opens structure without touching pH. Apply together or in rotation.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDry granular fertilisers\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eYes. A 2–5mm granule mixes evenly with other granular feeds in the spreader. Powdered gypsum does not — the fine stuff sinks to the bottom and comes out first.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCompost and organic amendments\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eYes, applied to the same ground. The two do different jobs and the combination beats either alone.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eManure or slurry, mixed in storage\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eNo. See the warning above.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eOther sulphur sources\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eCount the total. If you are already applying polyhalite, Epsom salt or an ammonium sulphate feed, reduce the gypsum accordingly.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eEricaceous plantings\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eYes, and this is where gypsum earns its keep. It has no effect on pH at all, so nothing you have done to acidify the soil for blueberries, rhododendrons, azaleas or camellias gets undone.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cdiv class=\"drf-callout\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eWhat to pair it with\u003c\/span\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"\/products\/organic-granulated-polyhalite-fertiliser-mined-yorkshire-14\"\u003eGranulated Polyhalite\u003c\/a\u003e: Yorkshire-mined, adds potassium alongside more calcium, magnesium and sulphur, and goes out of the same spreader.\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/products\/organic-granulated-volcanic-rock-minerals-basalt-soil-conditioner\"\u003eGranulated Rock Dust\u003c\/a\u003e: basalt, for the trace minerals gypsum does not carry.\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/products\/liquid-gypsum-micronised-calcium-sulphate\"\u003eLiquid Gypsum\u003c\/a\u003e: for spot-treating a patch, or an established lawn you would rather not walk a spreader across.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eWorth reading: \u003ca href=\"\/blogs\/the-dr-forest-blog\/how-to-feed-a-lawn-organically\"\u003ehow to feed a lawn the organic way\u003c\/a\u003e and \u003ca href=\"\/blogs\/the-dr-forest-blog\/organic-dry-amendments\"\u003ewhat organic dry amendments actually do\u003c\/a\u003e.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n\n\u003c!-- ══════════════ TAB 4 — RATES BY CROP ══════════════ --\u003e\n\u003cdiv id=\"drf-gg-panel4\" class=\"drf-panel\"\u003e\n\n\u003ch2\u003eRates by crop and site\u003c\/h2\u003e\n\n\u003cp\u003eThe sulphur rates below follow RB209, the national fertiliser guide British farmers work from, converted from kilos per hectare into grams per square metre at this product's 40% SO₃ analysis. RB209 is explicit that these are conditional: apply \u003cem\u003e\"where sulphur deficiency has been recognised or is expected.\"\u003c\/em\u003e The risk is highest on sandy soils in any rainfall, on loam and light silty soils in a wet region, and on clay only where more than 375mm of rain falls over the winter.\u003c\/p\u003e\n\n\u003ch3\u003eVegetables\u003c\/h3\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eCrop\u003c\/th\u003e\n\u003cth\u003eRate\u003c\/th\u003e\n\u003cth\u003eTiming \u0026amp; notes\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cstrong\u003eBrassicas\u003c\/strong\u003e — cabbage, sprouts, cauliflower, calabrese, kale, broccoli\u003c\/td\u003e\n\u003ctd\u003e12.5–18.8 g\/m²\u003c\/td\u003e\n\u003ctd\u003eAt or soon after planting. The hungriest group in the garden for sulphur, because the compounds that give cabbage and mustard their flavour are built from it. One trial lifted cauliflower yield by 25%.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eOnions, leeks, garlic, shallots\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003eAt or soon after planting. Onions and garlic build their heat and pungency out of sulphur. Trials show sulphur-fed bulbs taste noticeably sharper, though they do not grow any bigger.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePotatoes\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003eIn the seedbed. Gypsum is preferred to lime on acid ground because it adds calcium without raising pH.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePeas and beans\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003eAt or soon after planting. Peas and beans need sulphur to build protein, and to run the root nodules that fix their own nitrogen.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eTomatoes, peppers, chillies, aubergine\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m² for nutrition; 56–112 g\/m² pre-plant where soil calcium tests low\u003c\/td\u003e\n\u003ctd\u003eWorked into the bed before planting. Steady, even watering matters far more here than anything you add; see the note below.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCarrots, parsnips, beetroot, swede, turnip\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003eAt or soon after planting. On heavy ground it also means less clay clinging to the roots when you lift them.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eLettuce and leafy salads\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003eAt or soon after planting. No published source links gypsum to tipburn — that is caused by water stress and muggy, still conditions, not by a shortage of calcium.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCourgette, squash, pumpkin, cucumber\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003eAt or soon after planting.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eSweetcorn, radish, celery, asparagus, herbs\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e6–7 g\/m²\u003c\/td\u003e\n\u003ctd\u003eAt or soon after planting; early spring for established asparagus.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cdiv class=\"drf-callout drf-callout-gold\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eTomatoes and blossom end rot — the honest version\u003c\/span\u003e\n\u003cp\u003eCalcium only travels around a plant in the water the roots draw up. When a fruit is swelling fastest, the plant sends that water to the leaves in preference to the fruit, and the end of the fruit runs short no matter how much calcium is sitting in the soil. Californian extension research is direct about it: \u003cem\u003e\"Adding calcium to the soil rarely alleviates the problem.\"\u003c\/em\u003e Sprays on the leaves do not help much either, because calcium will not travel back down out of a leaf once it has arrived. Mulching and watering steadily does more than anything you can buy. Gypsum is worth adding where a soil test shows calcium genuinely is low. It is not a fix for erratic watering.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch3\u003eFruit\u003c\/h3\u003e\n\n\u003cp\u003eRB209 notes that \u003cem\u003e\"fruit crops are not generally thought to respond to sulphur\"\u003c\/em\u003e and recommends 15–25 kg SO₃\/ha only where deficiency is recognised or expected — roughly \u003cstrong\u003e4–6 g\/m²\u003c\/strong\u003e, applied in spring.\u003c\/p\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eCrop\u003c\/th\u003e\n\u003cth\u003eRate\u003c\/th\u003e\n\u003cth\u003eTiming \u0026amp; notes\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eApples and pears\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e0.9–1.4 kg per established tree, or 2.24–4.48 t\/ha across a block\u003c\/td\u003e\n\u003ctd\u003eLate autumn, spread on the ground under the branches, out as far as the outermost tips. One USDA review reports better rooting density and larger fruit where phosphogypsum was applied together with lime. Do not rely on it for bitter pit — the small sunken brown spots that appear in stored apples. That is about how calcium moves inside the fruit, not how much is in the ground.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eYoung fruit trees\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e4.5–9 kg per tree, spread under the branches\u003c\/td\u003e\n\u003ctd\u003eAt planting or in the first dormant season. Also 0.5–1 kg per tree is the garden-scale figure, watered in well.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eStrawberries, raspberries, currants\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e4–6 g\/m²\u003c\/td\u003e\n\u003ctd\u003eSpring. No gypsum-specific published rate exists for soft fruit; this is the RB209 fruit figure.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eBlueberries and other ericaceous fruit\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e4–6 g\/m², or as part of a container mix at 1 g\/litre\u003c\/td\u003e\n\u003ctd\u003eSpring. One of the few sensible ways to give an acid-loving plant calcium, since carbonate sources would undo your soil acidification. No gypsum-specific rate is published for ericaceous crops, so this is the RB209 fruit figure applied cautiously.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eOrnamentals\u003c\/h3\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003ePlanting\u003c\/th\u003e\n\u003cth\u003eRate\u003c\/th\u003e\n\u003cth\u003eTiming \u0026amp; notes\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eRoses\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e227–454g per bush\u003c\/td\u003e\n\u003ctd\u003eTwice a year, spring and autumn. Work lightly into the surface and soak.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eHerbaceous borders\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e200 g\/m² as a soil conditioner\u003c\/td\u003e\n\u003ctd\u003eAutumn or early spring, forked into the top 5cm before replanting.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eShrubs\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e450–900g per shrub\u003c\/td\u003e\n\u003ctd\u003eLate autumn, spread over the root area and watered in.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eEvergreens and conifers\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eAround 2.25kg per established tree\u003c\/td\u003e\n\u003ctd\u003eMid to late autumn.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eRhododendrons, azaleas, camellias, heathers\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e4–6 g\/m²\u003c\/td\u003e\n\u003ctd\u003eSpring. No effect on pH, so your carefully acidified soil stays acidic. As above, no rate is published specifically for acid-loving plants, so start low.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eField scale and grassland\u003c\/h3\u003e\n\n\u003cp\u003eUK sulphur recommendations from RB209, with the equivalent rate of this product at 40% SO₃.\u003c\/p\u003e\n\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eCrop\u003c\/th\u003e\n\u003cth\u003eRB209 rate\u003c\/th\u003e\n\u003cth\u003eThis product\u003c\/th\u003e\n\u003cth\u003eTiming\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eOilseed rape\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e50–80 kg SO₃\/ha\u003c\/td\u003e\n\u003ctd\u003e125–200 kg\/ha\u003c\/td\u003e\n\u003ctd\u003eLate February to early March\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eWinter and spring cereals\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e25–50 kg SO₃\/ha\u003c\/td\u003e\n\u003ctd\u003e62.5–125 kg\/ha\u003c\/td\u003e\n\u003ctd\u003eEarly March to end April\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eGrass for silage\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e40 kg SO₃\/ha per cut\u003c\/td\u003e\n\u003ctd\u003e100 kg\/ha per cut\u003c\/td\u003e\n\u003ctd\u003eBefore each cut\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eGrazed grass\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e20–30 kg SO₃\/ha per 100 kg N\/ha\u003c\/td\u003e\n\u003ctd\u003e50–75 kg\/ha\u003c\/td\u003e\n\u003ctd\u003eSpring and mid-season\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eForage brassicas, fodder beet\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e25 kg SO₃\/ha\u003c\/td\u003e\n\u003ctd\u003e62.5 kg\/ha\u003c\/td\u003e\n\u003ctd\u003eSoils at risk\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eSoil structure, arable\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e—\u003c\/td\u003e\n\u003ctd\u003e2.5–5 t\/ha\u003c\/td\u003e\n\u003ctd\u003eAfter harvest or early in a fallow, incorporated to 10cm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePhosphorus runoff mitigation\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e—\u003c\/td\u003e\n\u003ctd\u003e2.24 t\/ha\u003c\/td\u003e\n\u003ctd\u003eBroadcast where soil P is high; within 5 days after manure\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cdiv class=\"drf-callout\"\u003e\n\u003cspan class=\"drf-callout-title\"\u003eMaximum rates\u003c\/span\u003e\n\u003cp\u003eDo not exceed \u003cstrong\u003e1 kg per square metre in any single application or in any one year\u003c\/strong\u003e. In practice, garden rates should sit at or below 600 g\/m², and there is very little evidence that going higher achieves anything except washing magnesium and potassium out of the soil. If you are applying every year, get a soil test every few years to check where you have got to.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n\n\u003c!-- ══════════════ TAB 5 — FAQ ══════════════ --\u003e\n\u003cdiv id=\"drf-gg-panel5\" class=\"drf-panel\"\u003e\n\n\u003ch2\u003eFrequently asked questions\u003c\/h2\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq1\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq1\" class=\"drf-faq-q\"\u003eWhat is granulated gypsum and what does it do?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eIt is a naturally mined mineral — calcium sulphate — screened into 2–5mm granules. It does two jobs at once. It feeds plants calcium and sulphur in forms the roots can take up straight away, and it unsticks slumped clay: the calcium swaps places with the sodium clinging to the clay particles, and they clump into crumbs instead of collapsing into an airless pan. The analysis is 40% SO₃, 30% CaO and 3% MgO, which works out at 16% sulphur, 21% calcium and just under 2% magnesium.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq2\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq2\" class=\"drf-faq-q\"\u003eDoes gypsum really work on clay soil?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eOn some clays, dramatically. On others, not at all — and it is worth knowing which you have before you spend money. Gypsum works by swapping calcium in for sodium. If your clay is not carrying much sodium, there is nothing for the calcium to swap with and very little happens. British rain washes sodium out of most soils over time, so plenty of our clay is simply heavy rather than salt-affected. The RHS puts it as \u003cem\u003e\"some, but not all, clay soils respond to extra calcium\"\u003c\/em\u003e and suggests testing a small area first, which is exactly right. Mark out a few square metres, apply 400 g\/m², leave an untreated strip next to it, and compare the two after a winter. A rough field test in the meantime: squeeze a moist handful. If it crumbles when you open your hand, the structure is sound and compost will do more for it than gypsum will.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq3\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq3\" class=\"drf-faq-q\"\u003eDoes gypsum change soil pH?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eNo, and that is the main reason to choose it. Lime raises pH because the carbonate in it mops up acid. Gypsum contains no carbonate — it splits into calcium and sulphate, and neither has any effect on acidity. Field trials confirm no measurable change at normal rates; where any shift has been recorded at all it is slightly downward, a tenth to three tenths of a point. This is exactly why gypsum is the calcium of choice for blueberries, rhododendrons, azaleas and camellias. The flip side: it is not a substitute for lime, and it will not fix an acid soil.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq4\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq4\" class=\"drf-faq-q\"\u003eHow long does gypsum take to work?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eThe feeding side is quick — calcium and sulphur are available within weeks, because gypsum dissolves about 200 times more readily than ground limestone. As a rule of thumb, an inch of rain dissolves around 53 g\/m². The soil-structure side is slower. Expect noticeably softer, more workable soil within twelve months, and the full effect over two to three seasons. It is not a weekend job. In its favour, one study went back twenty-six years after a single application and could still measure the calcium a metre and a quarter down.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq5\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq5\" class=\"drf-faq-q\"\u003eGranulated or powdered gypsum — which should I buy?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eGranulated for anything you are spreading over an area: lawns, beds, allotments, paddocks, fields. It does not dust, spreads to 36 metres from a broadcast spreader, mixes evenly with other granular fertilisers in the spreader and dissolves gradually rather than all at once. Powder for potting mixes, small containers and precise dosing by the gram, where the extra surface area makes it dissolve faster. Powder is genuinely unpleasant to spread on a windy day.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq6\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq6\" class=\"drf-faq-q\"\u003eHow much gypsum do I need, and how far does a bag go?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eAt 200 g\/m² for general soil conditioning: 1.5kg covers 7.5 m², 4kg covers 20 m², 9kg covers 45 m², 15kg covers 75 m², 30kg covers 150 m². At the 50 g\/m² lawn maintenance rate those bags cover 30, 80, 180, 300 and 600 m². For heavy clay at 400 g\/m², halve the soil-conditioning coverage figures. For sulphur nutrition on vegetables the rate is far lower — 6 to 20 g\/m² — so a single 1.5kg bag will treat between 75 and 250 m².\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq7\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq7\" class=\"drf-faq-q\"\u003eIs gypsum good for lawns?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eOn lawns over clay, or where soil is compacted, waterlogged or salt-damaged, yes. Use 50–100 g\/m² in spring and autumn with a calibrated spreader, ideally before rain. The best return comes from applying 200 g\/m² straight after hollow-tining and brushing the granules into the tine holes — that gets the calcium down where the roots are, instead of leaving it sitting in the layer of dead grass on top. Be clear about what it does not do: gypsum does not decompact soil by itself. Aeration does the physical work; the calcium keeps the structure open afterwards.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq8\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq8\" class=\"drf-faq-q\"\u003eWill gypsum fix blossom end rot in my tomatoes?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eProbably not, and it is worth knowing why before you spend money. Blossom end rot is a plumbing problem far more than a feeding one. Calcium only travels around a plant in the water the roots draw up, and when a fruit is swelling fastest the plant sends that water to the leaves first. The end of the fruit runs short whatever is in the soil. Californian extension research puts it bluntly: adding calcium to the soil rarely helps, because it is primarily a water issue. Steady, even watering and a good mulch will do more than any product. If a soil test shows your calcium genuinely is low, gypsum is worth adding; if your watering has been up and down, fix that first.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq9\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq9\" class=\"drf-faq-q\"\u003eCan I use too much gypsum?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eYes, though you would have to try. Keep any single application at or below 1 kg per square metre, and in a garden there is rarely a reason to go above 600 g\/m². Overdo it and the surplus sulphate pairs up with magnesium and washes it out of the soil as Epsom salt, taking potassium with it. Field trials have found yields actually dropping at very heavy rates for that reason, and at ten times any garden rate one study recorded earthworm numbers halving over five months. If you are applying every year, get a soil test every few years to check where you are.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq10\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq10\" class=\"drf-faq-q\"\u003eIs gypsum safe around children, pets, bees and fish?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eYes. Calcium sulphate is non-caustic and non-toxic — it will not scorch grass or leaves the way a strong synthetic feed can, and it presents no hazard to children, pets, birds, bees or wildlife once spread and watered in. It is used deliberately in fish ponds to clear muddy water without killing fish, changing pH or harming livestock. Wash edible foliage before eating if you have applied granules over a growing crop. The one real hazard is chemical rather than biological: never mix gypsum into stored manure or slurry, because sulphate can be reduced to hydrogen sulphide under anaerobic conditions.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq11\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq11\" class=\"drf-faq-q\"\u003eIs this organic?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eIt is a naturally mined mineral rather than a manufactured or synthetic one, and it carries no animal by-products. Calcium sulphate is an inorganic mineral, so it is not an organic input in the chemical sense, and we hold no organic certification for it. Gypsum is widely accepted in organic and regenerative growing, and it works alongside no-dig, biodynamic and natural farming methods. If you are working to a specific certification standard, check your certifier's list of permitted inputs.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq12\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq12\" class=\"drf-faq-q\"\u003eCan I mix gypsum with other fertilisers?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eYes, with two provisos. Granular gypsum mixes evenly with other granular products in the spreader because the particle sizes match — powdered gypsum does not, and segregates. Applied to the same ground, it is compatible with lime, compost and every Dr Forest feed. Count your total sulphur: if you are already applying polyhalite, Epsom salt or an ammonium sulphate feed, reduce the gypsum accordingly. The exception is stored manure or slurry — apply gypsum to the ground after manure rather than mixing the two.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq13\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq13\" class=\"drf-faq-q\"\u003eWhen is the best time of year to apply it?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eAutumn is the classic timing for soil conditioning — after rough digging, or after aeration on turf — because winter rain does the dissolving for you. For sulphur nutrition, apply at or soon after planting, or in early spring for established crops; that is when the crop is building protein and when sulphate is least likely to have leached. Fine turf is best treated between late winter and early summer. Beyond that, granulated gypsum can go down any time of year when the ground is neither frozen nor waterlogged.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq14\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq14\" class=\"drf-faq-q\"\u003eHow is gypsum different from garden lime?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eBoth supply calcium; only lime changes your pH. Lime is calcium carbonate, and the carbonate mops up acid, which makes the soil more alkaline — useful if it is too acid, unhelpful if it is not. Gypsum is calcium sulphate, and it has no effect on acidity at all, so it feeds calcium to soil that is already where you want it. Gypsum also supplies sulphur, which lime does not, and dissolves roughly 200 times more readily, so it acts far faster. Where soil is both too acid and badly slumped, the answer is usually both: lime for the pH, gypsum for the structure.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq15\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq15\" class=\"drf-faq-q\"\u003eWhere does it come from, and where is it packed?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eIt is a naturally occurring mined calcium sulphate mineral, screened and granulated to 2–5mm. It is not gypsum scrubbed out of power station chimneys, not recycled plasterboard, and not phosphogypsum, a by-product of fertiliser manufacture. Those three industrial routes are where most cheap gypsum comes from. Mined rock avoids the mercury found in power station gypsum and the low-level radioactivity found in phosphogypsum entirely. It is bagged and dispatched by Dr Forest from Stockport, Greater Manchester.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"drf-faq\"\u003e\n\u003cinput id=\"drf-gg-faq16\" type=\"checkbox\"\u003e\u003clabel for=\"drf-gg-faq16\" class=\"drf-faq-q\"\u003eHow should I store it?\u003c\/label\u003e\n\u003cdiv class=\"drf-faq-a\"\u003e\u003cdiv\u003eDry, sealed and off a concrete floor. Granulated gypsum has an indefinite shelf life — it is a mineral, and nothing in it degrades — but it will absorb moisture from damp air and cake if the bag is left open. If it does cake, it has not lost any nutritional value; break it up and spread as normal. Keep it away from stored manure and slurry.\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@graph\": [\n    {\n      \"@type\": \"FAQPage\",\n      \"mainEntity\": [\n        {\n          \"@type\": \"Question\",\n          \"name\": \"What is granulated gypsum and what does it do?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"It is a naturally mined mineral, calcium sulphate, screened into 2-5mm granules. It does two jobs at once. It feeds plants calcium and sulphur in forms the roots take up straight away, and it unsticks slumped clay: the calcium swaps places with the sodium clinging to the clay particles, and they clump into crumbs instead of collapsing into an airless pan. The analysis is 40% SO3, 30% CaO and 3% MgO, which works out at 16% sulphur, 21% calcium and just under 2% magnesium.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Does gypsum really work on clay soil?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"On some clays, dramatically; on others, not at all. Gypsum works by swapping calcium in for sodium, so if your clay is not carrying much sodium there is nothing to swap with and very little happens. British rain washes sodium out of most soils over time, so plenty of our clay is simply heavy rather than salt-affected. The RHS says some, but not all, clay soils respond to extra calcium, and suggests testing a small area first. Mark out a few square metres, apply 400 g\/m2, leave an untreated strip beside it and compare after a winter. A rough field test: squeeze a moist handful, and if it crumbles when you open your hand the structure is sound and compost will do more than gypsum.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Does gypsum change soil pH?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"No, and that is the main reason to choose it. Lime raises pH because the carbonate in it mops up acid. Gypsum contains no carbonate, so it has no effect on acidity at all. Field trials confirm no measurable change at normal rates; where any shift is recorded it is slightly downward, a tenth to three tenths of a point. This is why gypsum is the calcium of choice for blueberries, rhododendrons, azaleas and camellias. The flip side is that it will not fix an acid soil either.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"How long does gypsum take to work?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"The feeding side is quick: calcium and sulphur are available within weeks, because gypsum dissolves about 200 times more readily than ground limestone. An inch of rain dissolves around 53 g\/m2. The soil-structure side is slower. Expect noticeably softer, more workable soil within twelve months and the full effect over two to three seasons. One study went back twenty-six years after a single application and could still measure the calcium a metre and a quarter down.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Granulated or powdered gypsum — which should I buy?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Granulated for anything you spread over an area: lawns, beds, allotments, fields. It does not blow about, it mixes evenly with other granular feeds in the spreader and it releases steadily rather than all at once. Powder for potting compost, small containers and precise dosing by the gram, where the finer grind dissolves faster. Powder is unpleasant to spread on a windy day.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"How much gypsum do I need, and how far does a bag go?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"At 200 g\/m2 for general soil conditioning: 1.5kg covers 7.5 m2, 4kg covers 20 m2, 9kg covers 45 m2, 15kg covers 75 m2, 30kg covers 150 m2. At the 50 g\/m2 lawn maintenance rate those bags cover 30, 80, 180, 300 and 600 m2.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Is gypsum good for lawns?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"On lawns over clay, or where the ground is compacted, waterlogged or salt-damaged, yes. Use 50-100 g\/m2 in spring and autumn with a walk-behind spreader, ideally just before rain. The best return comes from 200 g\/m2 straight after hollow-tining, brushed into the holes. Be clear about what does what: the aeration relieves the compaction, and the calcium then helps the new air spaces survive rather than closing straight back up.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Will gypsum fix blossom end rot in my tomatoes?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Probably not. Blossom end rot is a plumbing problem far more than a feeding one. Calcium only travels around a plant in the water the roots draw up, and when a fruit is swelling fastest the plant sends that water to the leaves first, so the end of the fruit runs short whatever is in the soil. Californian extension research puts it bluntly: adding calcium to the soil rarely helps, because it is primarily a water issue. Steady, even watering and a good mulch do more than any product.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Can I use too much gypsum?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Yes, though you would have to try. Keep any single application at or below 1 kg per square metre, and in a garden there is rarely a reason to exceed 600 g\/m2. Overdo it and the surplus sulphate pairs up with magnesium and washes it out of the soil as Epsom salt, taking potassium with it. Field trials have found yields dropping at very heavy rates for that reason, and at ten times any garden rate one study recorded earthworm numbers halving over five months.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Is gypsum safe around children, pets, bees and fish?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Yes. Calcium sulphate is non-caustic and non-toxic, presenting no hazard to children, pets, birds, bees or wildlife once spread and watered in. It is used deliberately in fish ponds to clear muddy water without killing fish or changing pH. Wash edible foliage before eating if applied over a growing crop. Never mix gypsum into stored manure or slurry, because sulphate can be reduced to hydrogen sulphide under anaerobic conditions.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Is this organic?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"It is a naturally mined mineral rather than a manufactured one, and it carries no animal by-products. Calcium sulphate is inorganic, so it is not an organic input in the chemical sense, and we hold no organic certification for it. Gypsum is widely accepted in organic and regenerative growing and works alongside no-dig, biodynamic and natural farming methods.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Can I mix gypsum with other fertilisers?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Yes. Granular gypsum mixes evenly in the spreader with other granular products because the particle sizes match; powdered gypsum separates out. Applied to the same ground it works alongside lime, compost and every Dr Forest feed. Count your total sulphur if you are also using polyhalite, Epsom salt or an ammonium sulphate feed. The one exception is stored manure or slurry: spread gypsum on the ground after manure rather than mixing the two.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"When is the best time of year to apply it?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Autumn is the classic timing for soil conditioning, after rough digging or after aeration on turf, because winter rain does the dissolving. For sulphur nutrition, apply at or soon after planting, or early spring for established crops. Fine turf is best treated between late winter and early summer. Otherwise any time the ground is neither frozen nor waterlogged.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"How is gypsum different from garden lime?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Both supply calcium; only lime changes your pH. Lime is calcium carbonate, and the carbonate mops up acid, making soil more alkaline. Gypsum is calcium sulphate, which has no effect on acidity, so it feeds calcium to soil that is already where you want it. Gypsum also supplies sulphur, which lime does not, and dissolves roughly 200 times more readily, so it acts far faster. Where soil is both too acid and badly slumped, the answer is usually both.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"Where does it come from, and where is it packed?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"It is a naturally occurring mined mineral, screened and granulated to 2-5mm. It is not gypsum scrubbed out of power station chimneys, not recycled plasterboard, and not phosphogypsum, a by-product of fertiliser manufacture. Those three industrial routes are where most cheap gypsum comes from. Mined rock avoids the mercury found in power station gypsum and the low-level radioactivity found in phosphogypsum entirely. It is bagged and dispatched by Dr Forest from Stockport, Greater Manchester.\"\n          }\n        },\n        {\n          \"@type\": \"Question\",\n          \"name\": \"How should I store it?\",\n          \"acceptedAnswer\": {\n            \"@type\": \"Answer\",\n            \"text\": \"Dry, sealed and off a damp concrete floor. Granulated gypsum has an indefinite shelf life, but it absorbs moisture from damp air and will cake if left open. Caking does not reduce nutritional value — break it up and spread as normal. Keep away from stored manure and slurry.\"\n          }\n        }\n      ]\n    },\n    {\n      \"@type\": \"HowTo\",\n      \"name\": \"How to apply granulated gypsum\",\n      \"description\": \"Applying granulated gypsum for soil conditioning, lawn care and crop nutrition.\",\n      \"supply\": [\n        {\n          \"@type\": \"HowToSupply\",\n          \"name\": \"Granulated gypsum 2-5mm\"\n        }\n      ],\n      \"tool\": [\n        {\n          \"@type\": \"HowToTool\",\n          \"name\": \"Broadcast or drop spreader\"\n        },\n        {\n          \"@type\": \"HowToTool\",\n          \"name\": \"Garden fork or rotavator\"\n        },\n        {\n          \"@type\": \"HowToTool\",\n          \"name\": \"Hose or watering can\"\n        }\n      ],\n      \"step\": [\n        {\n          \"@type\": \"HowToStep\",\n          \"name\": \"Choose the right rate\",\n          \"text\": \"Decide whether you are feeding sulphur and calcium (6-20 g\/m2) or changing soil structure (200-600 g\/m2). The rates differ by a factor of ten to thirty. Weigh out for the area rather than estimating.\"\n        },\n        {\n          \"@type\": \"HowToStep\",\n          \"name\": \"Test a patch on clay\",\n          \"text\": \"Mark out a few square metres, treat at 400 g\/m2, leave an untreated strip beside it and compare after a winter. Some clays respond dramatically and some barely at all.\"\n        },\n        {\n          \"@type\": \"HowToStep\",\n          \"name\": \"Spread evenly\",\n          \"text\": \"Use a spreader for anything over a few square metres, or spread by hand in two passes at right angles for small beds. A walk-behind spreader throws two to four metres; set it to half rate and do two overlapping passes rather than one heavy one.\"\n        },\n        {\n          \"@type\": \"HowToStep\",\n          \"name\": \"Incorporate where possible\",\n          \"text\": \"Fork or rotavate into the top 5-10cm on bare ground; rates above 250 g\/m2 work considerably better dug in than left on top. On an established lawn, leave it on the surface and let the rain carry it down.\"\n        },\n        {\n          \"@type\": \"HowToStep\",\n          \"name\": \"Water it in\",\n          \"text\": \"Granules need moisture before anything happens. An inch of rain dissolves around 53 g\/m2 of gypsum, so put it down before rain if you can and save yourself the hose.\"\n        },\n        {\n          \"@type\": \"HowToStep\",\n          \"name\": \"Allow time and reassess\",\n          \"text\": \"Calcium and sulphur are available within weeks. Soil structure takes longer: noticeably softer ground within twelve months, and the full benefit over two to three years.\"\n        }\n      ]\n    }\n  ]\n}\n\u003c\/script\u003e\n\u003c\/div\u003e\n","brand":"Dr Forest","offers":[{"title":"1.5kg","offer_id":58371392766326,"sku":"DF-GYPGRAN-1.5","price":10.49,"currency_code":"GBP","in_stock":true},{"title":"4kg","offer_id":58371392799094,"sku":"DF-GYPGRAN-4","price":19.35,"currency_code":"GBP","in_stock":true},{"title":"9kg","offer_id":58371392831862,"sku":"DF-GYPGRAN-9","price":30.99,"currency_code":"GBP","in_stock":true},{"title":"15kg","offer_id":58371392864630,"sku":"DF-GYPGRAN-15","price":44.49,"currency_code":"GBP","in_stock":true},{"title":"30kg","offer_id":58371392897398,"sku":"DF-GYPGRAN-30","price":89.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0049\/8194\/8504\/files\/sulfcal.jpg?v=1785520961","url":"https:\/\/www.drforest.co.uk\/products\/granulated-gypsum-clay-breaker","provider":"Dr Forest","version":"1.0","type":"link"}