Granulated Gypsum
Granulated Gypsum is natural calcium sulphate in a granular form instead of a fine powder, so it broadcasts evenly with little dust. It supplies calcium and sulphur without changing soil pH and is used to open up clay and treat high sodium soils.
At a glance
- Type: amendment (calcium sulphate, granular)
- Supplier certificate on file: BioGro licence 297. See the certificate and its dates.
- Analysis: calcium (Ca) 22%, sulphur (S) 18% (calcium sulphate dihydrate)
- Use for: calcium and sulphur without a pH change, clay soils, high sodium soils, broadcast application
- Rate: 250 to 600 g per square metre, sized from a soil test, dug in and watered
- Form: granules, low dust
What it is
Granulated gypsum is the same mineral as our powdered gypsum, calcium sulphate dihydrate, formed into granules. The granular form is suited to broadcasting by hand or spreader and keeps dust down. Typical analysis: calcium (Ca) 22%, sulphur (S) 18%.
What it does
- Gypsum is calcium sulphate, a neutral salt. It supplies calcium and sulphur but does not neutralise acid, so it adds calcium without lifting pH.
- Calcium helps clay particles bind into crumbs, which is why gypsum is used to open up heavy clay and improve drainage and root depth.
- Calcium from gypsum displaces sodium from clay, the standard treatment for sodic soils.
- Gypsum dissolves slowly in soil water over months, releasing calcium and sulphur together. It is more soluble than lime, so its calcium moves down into the root zone.
- Sulphur builds proteins, oils and flavour compounds. A shortage shows as pale young leaves.
Analysis
- Calcium (Ca) 22%
- Sulphur (S) 18%
How to use
- Vegetables: 250 to 600 g per square metre of soil, sized from the calcium and sulphur shortfall on a soil test. Dig in and water in.
- Flowers: 250 g per square metre, mixed and watered into the soil.
- Soil test first. Our fertiliser calculator (/pages/fertiliser-calculator) offers gypsum at 250, 400 or 600 g per square metre for a tested shortfall.
Watch out
- Gypsum does not raise pH. If the soil is acid and calcium is low, lime is the tool, not gypsum.
- Granules dissolve more slowly than powder, so allow longer before judging the result.
- Gypsum leaches in a wet climate. Retest rather than reapplying by habit.
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Handling and storage
- Wear a mask to avoid inhaling particles and open the bag in a well ventilated area.
- Wear gloves and eye protection, and wash hands after use.
- Once opened, keep sealed and dry.
- If swallowed, or if the product gets into the eyes or irritates the skin, rinse the area well and call the National Poisons Centre on 0800 POISON (0800 764 766).
Shipping and returns
We ship nationwide across New Zealand. Orders are usually dispatched within 1 to 2 business days and rural delivery can take longer. Unopened products can be returned within 30 days.
