Liquid gypsum · FAQ

Your liquid gypsum questions, answered

Seventeen questions, each answered in full on its own page. Start with whichever one is yours.

Dr Forest Liquid Gypsum, white bottle with ribbed cap

Mined natural mineral

Liquid Gypsum

Micronised natural calcium sulphate with fulvic acid, for clay soil and calcium feeding. 500ml · 1 litre

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19.55% Calcium15.31% Sulphur5µm average particleZero neutralising value

This page is an index, not the product. Below are seventeen questions gardeners actually ask, each answered in full on its own page, with sources: what it is, how it works on clay, the rates and timings, the safety, and the places where the evidence runs out.

For the product itself, its full analysis and how to use it, see Dr Forest Liquid Gypsum, which comes in 500ml and 1 litre alongside the rest of the liquid range.

Not sure where to start?

If your question is whether it will do anything in your particular garden, begin with a crumb of your own soil in a jar of rainwater. Nobody has surveyed how much British garden clay actually disperses, which is why that test is worth more to you than any average: it costs nothing and it tells you about your own soil.

Every question, answered

What it is (micronised calcium sulphate) →Micronised natural calcium sulphate, suspended in fulvic acid.What it does on clay →Feeds calcium and sulphur, and helps dispersive clay drain, without raising pH.How the calcium mechanism works →Calcium gathers dispersed clay into crumbs so water gets through. Strongest on dispersive clay.Dispersion test: will it help your clay? →On dispersive clay, yes. On clay that does not disperse, the structural effect is small, not nil.What ‘clay breaker’ actually means →A marketing term, not soil science. Nothing breaks clay; gypsum is the active ingredient in most clay improvers.Why is my garden soil sticky and heavy? →Because it is clay. Texture is fixed, structure is not, and structure is where the effort goes.Why is my soil like concrete when it dries out? →Usually capping rather than compaction. Dig down with a trowel and find out which you have.Why does clay soil crack in summer? →Clay minerals shrink as they dry. Normal behaviour, and no feed or conditioner stops it.How to apply (rates and watering can) →Shake, dilute, water on. Lawn clay conditioning: 15 ml/L at 1 L/m² fortnightly for three months.How often and when →One rate carries a frequency: lawn clay conditioning, fortnightly for three months. Otherwise repeat on the symptom.How long before you see change →We do not put a clock on it, and the effect is durable rather than permanent.On lawns and turf →Yes, especially on clay, because it works without digging in. Lawn rates inside.Why is moss taking over my lawn? →Moss fills gaps, it does not create them. Change the conditions, not the moss.Liquid vs granular gypsum →Same mineral, calcium sulphate. The liquid dissolves faster, by surface area, and needs no digging in.Does it change soil pH? →Its neutralising value is zero, so it is not a liming material. Use lime if you need to raise pH.Pets and children →Keep pets and children off while you are applying it, and treat it as you would any garden concentrate.Can you use too much? →You can. Stick to the rates, and do a dispersion test to check gypsum has a job to do.

Start here if you have clay

Start with a crumb of your own soil in a jar of rainwater, because no average tells you what your clay actually does. The full dispersion test →

Dr Forest Liquid Gypsum, white bottle with ribbed cap

Ready to buy?

Liquid Gypsum

19.55% calcium and 15.31% sulphur (27.35% CaO, 38.23% SO₃), milled to a 5 micron average and suspended in fulvic acid.

Zero neutralising value, not a liming material · No digging in · Mined mineral · No synthetic dispersants · 500ml and 1 litre

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Sources

  1. Oster, J.D., Shainberg, I. and Wood, J.D. (1980). Flocculation value and gel structure of sodium/calcium montmorillonite and illite suspensions. Soil Science Society of America Journal 44(5), 955–959.
  2. GRDC (2020). Dealing with dispersive soils. Western region fact sheet.
  3. Anderson, G.C. et al. (2021). Agronomy 11(5), 826.
  4. Lingenfelter, D. and Beegle, D.B. Soil acidity and aglime. Penn State Extension.
  5. Fleuridor, L. et al. (2021). Agronomy Journal 113(5), 4220–4230.
  6. Chen, L. and Dick, W.A. (2011). Gypsum as an agricultural amendment, Bulletin 945. Ohio State University Extension.
  7. Royal Horticultural Society. Clay soils. rhs.org.uk

Soil notes

Get the evidence, not the marketing

Occasional notes from Stockport on feeding, soil structure and what the research actually supports, including the things that turn out not to work.

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