Year planner · Liquid Gypsum, micronised calcium sulphate
Liquid gypsum calculator: a year's supply, worked out.
Tell it what you grow and it plans the next twelve months: every application date, the mix each time, the total you need and the cheapest bottles to cover it. Every rate is the one on the product page.
What are you growing?
Set a number for each crop you grow and leave the rest at 0. The plan updates as you go.
More vegetables and clay soil
The product page gives every two to four weeks through the growing season.
Mix around each plantThe product page gives 200–500 ml of mix per plant, the higher volume for a large plant in the ground. Beds and lawns take 1 litre of mix per square metre.
Seasons are typical for a UK garden. Move any date in your calendar to suit your own.
Your year of liquid gypsum
Buy the year in one go
Your year, month by month
Each application, crop by crop
| Crop | Rate | Each time | Across the year |
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Every date in the plan
Gypsum on the farm: what the trials show
Farmers use gypsum as a source of calcium and sulphur and to steady soils whose clay disperses. The trials below were run at field scale with solid gypsum, so they show what calcium and sulphur do for a crop rather than what any one product will do in a garden. Read together, they say the same thing: gypsum pays where calcium or sulphur is short, or where the soil seals and sheds water, and where neither is the problem the harvest rarely changes.
Tomatoes · about 30% more fruit
A heavier crop on soil that dispersed.
On alluvial soil at Carnarvon, Western Australia, gypsum lifted the yield of determinate tomatoes from 31.9 to 41.5 tonnes a hectare and significantly reduced dispersion of the soil clay. Irrigation made the larger difference of the two, which is why steady watering comes first.
Muller (1993), Australian Journal of Experimental Agriculture 33(6): 803–806.
Groundnuts · less pod rot
Calcium where the fruit forms.
Groundnut pods develop underground and take their calcium directly from the soil. On a low-calcium loamy sand in Georgia, pod rot was severe without gypsum and eased as the rate rose; at a second site with about twice the soil calcium, gypsum made no difference to yield.
Walker and Csinos (1980), Peanut Science 7(2): 109–113; Arnold et al. (2017), Peanut Science 44(1): 13–18.
Grain crops · 7 to 14% more
Deeper roots in acid subsoil.
A 2020 meta-analysis of gypsum on acid, no-till soils found grain yields rose on average by 14% where crops ran short of water and by 7% where they did not. In south-eastern and central-western Brazil, gypsum to improve the root zone of tropical soils is a widespread practice with established recommendations.
Pias et al. (2020), Agronomy Journal 112: 675–692; Tiecher et al. (2018), Revista Brasileira de Ciência do Solo 42.
Sulphur · UK farms
Sulphur no longer falls from the sky.
UK crops once took much of their sulphur from the air. With sulphur dioxide emissions far lower over the past fifty years, the AHDB treats deficiency as a growing risk, and its Nutrient Management Guide (RB209) names brassica vegetables and potatoes as at risk, alongside cereals, peas, grass and oilseed rape. The sulphur in gypsum is sulphate, the form roots take up.
AHDB, Sulphur management for yield and quality in wheat; Potash Development Association summary of RB209 (2017).
Where it did nothing
Enough is enough.
In 62 Ohio trials using gypsum as the sulphur source, yield rose in four. Georgia groundnuts on soils already holding adequate calcium gave no extra yield, though the seed took up more calcium. Ohio State University Extension sums up its own state's trials plainly: positive yield responses to gypsum are rare.
Fleuridor et al. (2023), summarised by Ohio State University Extension, ANR-0153 (2024); Arnold et al. (2017).
In the garden
Where it earns its place.
Pots, grow bags, peat-free and coir composts, light sandy soil and heavy potash feeding are where calcium supply can genuinely run short. Clay that disperses in rainwater is where the sulphate does its structural work. On a well-limed, well-fed loam, expect little, and spend the money elsewhere.
See the dispersion test below before starting a clay course.
- Muller AT (1993). Effect of gypsum, deep ripping, and irrigation on determinate tomatoes. doi:10.1071/EA9930803
- Walker ME, Csinos AS (1980). Effect of gypsum on yield, grade and incidence of pod rot in five peanut cultivars. doi:10.3146/i0095-3679-7-2-13
- Arnold JA, Beasley JP, Harris GH, Grey TL, Cabrera M (2017). Effect of gypsum application rate, soil type, and soil calcium on yield, grade and seed quality of runner type peanut cultivars. doi:10.3146/PS16-16.1
- Pias OHC, Tiecher T, Cherubin MR, Silva AGB, Bayer C (2020). Does gypsum increase crop grain yield on no-tilled acid soils? A meta-analysis. doi:10.1002/agj2.20125
- Tiecher T, Pias OHC, Bayer C, Martins AP, Denardin LGO, Anghinoni I (2018). Crop response to gypsum application to subtropical soils under no-till in Brazil: a systematic review. doi:10.1590/18069657rbcs20170025
- AHDB. Sulphur management for yield and quality in wheat. ahdb.org.uk; Potash Development Association (2017). AHDB Nutrient Management Guide (RB209). pda.org.uk
- Fleuridor L, Fulford A, Lindsey LE, Lentz E, Watters H, Dorrance A, Minyo R, Richer E, Chaganti V, Kumaran S, Culman SW (2023). Ohio grain crop response to sulfur fertilization. doi:10.1002/agj2.21328
- Rakkar M, LaBarge G (2024). Response of soils and crops to gypsum application in Ohio. Ohio State University Extension ANR-0153. ohioline.osu.edu
Before you start
How to apply
Shake, dilute fresh, water it in.
Shake the bottle hard for 30 seconds, because the gypsum settles: no synthetic dispersant holds it up. Stir the concentrate into a splash of warm water in a jug, add it to the rest of the water in the can, and use it the same day. Beds and lawns take 1 litre of mix per square metre; plants take their share around the base rather than over the crown. Water in afterwards. Store the bottle sealed, above 5°C and out of direct sun, and use it within 12 months of purchase, which is why the planner stops at a year.
Clay that puddles
Do the dispersion test first.
Drop an air-dried crumb of soil from about 10 cm down into a glass of rainwater, not tap water, which carries enough calcium to skew it. A milky halo at ten minutes or two hours means the clay disperses and the course has a job to do. A hole 30 cm deep that is still full of water after 24 hours points to a high water table, a pan or no fall, which needs physical drainage. Gypsum does not relieve compaction. The full test.
Gypsum, not lime
Calcium without the pH change.
Gypsum is a neutral salt with a neutralising value of zero: it will not correct an acid soil, and it will not push a soil that is already at the right pH towards alkaline. The sulphate is plant-available at once, with no microbial conversion. If your soil is both acid and short of calcium, lime is the right product: Garden Lime for a quicker correction, or Sea Shell Meal for slow, long-term liming.
Marked tomato fruit
Steady watering first, then the calcium.
Blossom end rot is mostly a calcium delivery problem: calcium travels in the water a plant draws up, so dry spells and erratic watering starve the fastest-growing tissue at the blossom end. Supply can genuinely run short too, in pots, grow bags, peat-free and coir composts, light sandy soil and under heavy potash feeding, and that is where a calcium drench earns its place. Keep the compost evenly moist first. Blossom end rot in tomatoes, in full.
Shake it, dilute it fresh, and water it where the roots are.Liquid Gypsum · Liquid fertiliser calculator · What liquid gypsum is