Soil Conditioner
Humic Acid Granules | 100% Soluble, 70% Humic Acid
70% humic acid to improve soil structure and uptake.
from £7.99
How to mix
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Mix in a heatproof mug with a little boiling water
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Stir 60 seconds
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Dilute
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Liquid Gypsum for clay soil and lawns: micronised calcium sulphate
If water sits on your lawn or beds after rain, the cause is often a sealed surface: rain breaks bare clay into fine particles that clog the top few millimetres. Liquid gypsum is natural calcium sulphate, mined, milled to a 5 micron average and suspended in water, so you can water it on with no digging and no lifting turf. Gypsum mixed into the surface water keeps the clay particles together, so the surface stays open and rain soaks in. It also supplies calcium and sulphur without changing soil pH.
- For water that sits after rain. Gypsum stops a clay surface sealing over. It works hardest on clay that comes apart in water, and a quick crumb test tells you whether yours does.
- Reaches clay you can't dig. Watered onto established lawns and borders, no lifting or forking.
- Spring or autumn. Three monthly applications in autumn and three in spring, finished by the end of May.
- Calcium and sulphur for plants. Before planting and again before flowering or fruiting, with no change to soil pH.
- Pairs with the wetting agent. Natural Wetting Agent in the same can gives better ground penetration and better results on a crusted lawn.
19.55% Ca (27.35% CaO)
15.31% S (38.23% SO₃)
5 μm average particle
No change to soil pH
Naturally mined
Packed in Stockport
Part of our clay soil range. Not sure gypsum will help? Take the two-minute test or read liquid gypsum for clay soil.
What's in Liquid Gypsum
A thick, creamy suspension: the micronised gypsum is physically present in the liquid, which is why it is opaque.
Natural gypsum (calcium sulphate), micronised
Mined and milled to a 5 micron average. 19.55% w/v calcium (195 g per litre) and 15.31% w/v sulphur.
Fulvic acid
Added to the suspension.
Water
The carrier, so it can be diluted in a watering can or sprayer.
How to use Liquid Gypsum: tests, rates and timing
Is gypsum the answer? Four tests before you buy
Waterlogging has three causes: a sealed surface, a compacted layer, or water with nowhere to go. Gypsum stops the first. These tests tell you which you have. You need a long screwdriver, a spade, a glass and some rainwater.
- Ribbon test: is it clay at all? Squeeze a lump of moist soil between thumb and forefinger into a flat ribbon. Clay forms a smooth, shiny ribbon 5 cm or longer. No ribbon: your problem is not clay, so look at the other two causes.
- Crumb test: does your clay come apart in water? Take a crumb of soil from about 10 cm down and let it dry. Drop it into a glass of rainwater, leave it still, and look at ten minutes and again at two hours. A milky halo spreading from the crumb: your clay disperses, so it seals over in rain, and gypsum is the fix. Clear water: your clay holds together. Gypsum still helps where the surface seals over after rain, though less than on clay that disperses; check for compaction and drainage too. Full protocol: does liquid gypsum work on clay soil?
- Screwdriver test: is it compacted? Push a long screwdriver into moist soil. Uncompacted soil usually lets it in 15 to 20 cm under moderate hand pressure. A hard layer within 5–10 cm: a compaction pan. Fork, broadfork or hollow-tine aerate it first, then apply gypsum straight afterwards.
- Hole test: has the water anywhere to go? Dig a hole 30 cm deep and 30 cm wide in the wettest spot, fill it with water and time it. Still full after 24 hours: a high water table, a subsoil pan or no gradient. No liquid product will fix that; you need physical drainage, such as a French drain, a soakaway or raised beds.
What your results mean
Ribbon, milky halo, and the hole drains within a day: your surface is sealing. Run the programme below.
Screwdriver stops short: aerate first, then apply gypsum straight afterwards.
Hole still full the next day: do not buy gypsum for this. It needs drainage work.
Clear water in the glass: your clay holds together. Gypsum works hardest on clay that disperses, but it still helps where the surface seals over after rain, though less. Run the compaction and hole tests, work in organic matter, and keep off the clay when it is wet.
On a lawn
Lawn rates
Lawn: general maintenance
The standard lawn rate for an ongoing supply of calcium and sulphur. Apply with a watering can fitted with a rose, or through a knapsack sprayer, and water in lightly afterwards.
Lawn on clay that puddles
For lawns on clay where the surface seals and sits wet after rain. Apply in September, October and November, then in March, April and May. The reasoning is on The Science tab.
Lawn: after aeration or scarifying
Apply straight after hollow-tine aeration, slit aeration or scarifying, while the channels are open. To be straight about it, no trial compares gypsum put down through core holes with gypsum left on the surface. Aerate because compaction needs aerating: gypsum does not relieve compaction, and a two-year Ohio study found no change in penetration resistance after gypsum (Rakkar & LaBarge 2024, Ohio State University Extension ANR-0153).
How much do I need?
At the maintenance rate, 10 ml per litre at 1 litre of mix per m²:
| Size | Covers per application |
|---|---|
| 500 ml | 50 m² |
| 1 litre | 100 m² |
| 5 litres | 500 m² |
| 2 x 5 litres | 1,000 m² |
At the clay rate it covers less; the figures are under the clay programme below, and the liquid gypsum calculator works it out for your lawn.
When to apply on a lawn
| Months | What to do |
|---|---|
| September to November | Main window. The first three monthly clay applications, before the winter rain. |
| December to February | Only to finish an autumn programme. Never on frozen, snow-covered or waterlogged ground. |
| March to May | The second three monthly clay applications, finished by the end of May. |
| June to August | Maintenance rate only, if at all. |
Never apply into standing water: wait until the puddles have gone.
How to mix and apply
- Measure into a heatproof mug or jar. Add a small amount of boiling water and stir for 60 seconds until it is mixed.
- Dilute with the rest of your water. Pour into the watering can or sprayer and stir briefly. If you are using the wetting agent, add that to the can first.
- Apply evenly and water in lightly. Use a rose or a knapsack sprayer, walking the lawn in strips.
- Use it fresh. Mix only what you need, and never store it diluted.
The clay programme: six monthly applications
Lawns, beds and borders on clay that seals over
Apply in September, October and November, then in March, April and May. Water the mix evenly over the area from a can with a rose or a knapsack sprayer, around plants and off their crowns. Never apply to frozen, snow-covered or waterlogged ground, or into standing water. On heavy clay you are actively improving, run the programme in the years you need it and expect to come back to it about every three years.
How much do I need for clay?
At the clay rate, 15 ml per litre at 1 litre of mix per m²:
| Size | Per application | Full year (six applications) |
|---|---|---|
| 500 ml | 33 m² | 5.5 m² |
| 1 litre | 66 m² | 11 m² |
| 5 litres | 333 m² | 55 m² |
| 2 x 5 litres | 666 m² | 111 m² |
For your own area, use the liquid gypsum calculator.
The plant programme
Baseline: two applications
1. Before planting. Water the mix over the bed at 1 litre per m², or over the planting area for individual plants.
2. Before flowering or fruiting. Drench around the root zone, keeping it off the crown: 1 litre per m² over a bed, or 200–500 ml per plant for individual plants. For fruit trees and bushes, use the bed rate over the area under the canopy.
Stepping it up: up to every other week
For a steady supply through the season, repeat the drench as often as every other week. Use 10 ml per litre for calcium-hungry crops such as tomatoes, peppers and apples while the fruit is swelling, or where a soil test shows calcium is genuinely low, then return to 5 ml per litre.
Foliar spray
Foliar calcium trials have used soluble calcium salts rather than gypsum, so the drench is the main route and the spray an extra. Spray in the early morning or evening, out of full sun; it may leave a white residue.
| Stage | Rate | How |
|---|---|---|
| Before planting | 5 ml per litre | 1 L/m² over the bed or planting area |
| Before flowering or fruiting | 5 ml per litre | 1 L/m², or 200–500 ml per plant |
| Through flowering and fruiting (optional) | 5 ml per litre | Up to every other week |
| Fruit fill, calcium-hungry crops | 10 ml per litre | Then back to 5 ml per litre |
| Foliar (optional extra) | 5 ml per litre | Filtered, early morning or evening |
Mixing and compatibility
Measure into a heatproof mug or jar, add a small amount of boiling water and stir for 60 seconds until mixed, then dilute it in the can. Use it fresh. It mixes with most feeds, but keep it out of the same can as any phosphate feed. For a fully soluble calcium feed without the sulphur, see Amino Chelated Calcium.
How Liquid Gypsum works
Gypsum works while it is in the water on the soil surface, during rain. It does not need sodium in your soil to work.
- It keeps the surface open. Under simulated rain, surface gypsum roughly doubled how fast water soaked into two of three soils, because gypsum mixed into the water kept the clay particles together [Miller 1987].
- It works hardest on clay that comes apart. Surface gypsum cut soil loss sharply from dispersive soils and less from nondispersive ones [Ben-Hur et al. 1992], which is why the crumb test comes first.
- Little and often. In a four-year Ohio trial, frequent lower rates did better than one large application [Chaganti et al. 2019], which is why the clay programme is monthly.
Those rainfall trials used 5 tonnes per hectare of phosphogypsum. The clay programme here puts down roughly 75 g of mined, micronised gypsum per square metre a year. Gypsum does not break up a compacted layer, lower a high water table or stand in for a drain.
References
- Miller, W.P. (1987). Infiltration and soil loss of three gypsum-amended Ultisols under simulated rainfall. Soil Science Society of America Journal, 51(5), 1314–1320. doi:10.2136/sssaj1987.03615995005100050040x
- Ben-Hur, M., Stern, R., van der Merwe, A.J. & Shainberg, I. (1992). Slope and gypsum effects on infiltration and erodibility of dispersive and nondispersive soils. Soil Science Society of America Journal, 56(5), 1571–1576. doi:10.2136/sssaj1992.03615995005600050039x
- Chaganti, V.N., Culman, S.W., Dick, W.A. & Kost, D. (2019). Effects of gypsum application rate and frequency on corn response to nitrogen. Agronomy Journal, 111(3), 1109–1117. doi:10.2134/agronj2018.10.0683
Figures from published research are not a trial of this product.
Use Liquid Gypsum with
- Natural Wetting Agent: better ground penetration and better results; add it to the can first. Both together: Liquid Gypsum and Wetting Agent, 10% less than buying them separately.
- Granulated Gypsum for Clay Soil: for digging into beds by the square metre before planting.
- Chelated Calcium Spray for Plants: a fully soluble calcium without the sulphur.
Which to choose: use granules where you can dig and the liquid where you can't. For clay you can dig, granules deliver several times more calcium per square metre for a similar cost. Work out your quantity with the liquid gypsum calculator.
Liquid Gypsum FAQs
It will where the waterlogging starts at a sealed surface on clay: it keeps the surface open, so rain soaks in. It does most on clay that comes apart in water and less on clay that holds together. It will not fix compaction, a high water table, a subsoil pan or poor grading. The four tests on the How to Use tab tell you which you have.
Do the crumb test: drop a dry pea-sized crumb from about 10 cm down into a glass of rainwater and look at ten minutes and two hours. A milky halo means your clay disperses and gypsum has most to do. Clear water means your clay holds together: gypsum still helps where the surface seals over after rain, though less, so check for compaction and drainage too.
15 ml per litre at 1 litre of mix per m², monthly: three times in autumn (September to November) and three in spring (March to May). Each litre covers about 66 m² per application.
Maintenance is 10 ml per litre at 1 litre per m². For a lawn on clay that puddles, follow the clay programme at 15 ml per litre.
Autumn and spring for clay, before planting and before flowering for plants. In winter, only to finish an autumn programme. Never onto frozen, snow-covered or waterlogged ground, or into standing water.
Measure it into a heatproof mug, stir in a little boiling water for 60 seconds, then dilute in the can. Mix only what you need and use it fresh.
No. Gypsum is a neutral salt. If your soil is both acid and short of calcium, lime is the right product instead.
Treat it as any garden concentrate: store it out of reach and keep pets and children off while you apply it. Once a drench has soaked in or a spray has dried, we know of no reason to keep them off. More at is liquid gypsum safe for pets and children?
Buy as a pair and save 10%
Liquid Gypsum and Wetting Agent
Natural Wetting Agent in the same can helps the water, and the gypsum carried in it, soak in evenly instead of running off to the low spots.
Matched to your size: 500 ml each
£24.29
£26.99 bought separately
You save £2.70 (10%)
Buy as a pair and save 10%
Liquid Gypsum and Wetting Agent
Natural Wetting Agent in the same can helps the water, and the gypsum carried in it, soak in evenly instead of running off to the low spots.
Matched to your size: 1 litre each
£37.79
£41.99 bought separately
You save £4.20 (10%)
Buy as a pair and save 10%
Liquid Gypsum and Wetting Agent
Natural Wetting Agent in the same can helps the water, and the gypsum carried in it, soak in evenly instead of running off to the low spots.
Matched to your size: 5 litres each
£137.69
£152.99 bought separately
You save £15.30 (10%)
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