Although most gypsum is used in the building industry, an increasing proportion is now being used in agriculture and
horticulture. Here, it is very useful for improving the textural and drainage properties of heavy (clay) soils. Gypsum
is also an excellent calcium and sulphur fertiliser. Its special benefits are that horticultural gypsum is fast acting
and pH neutral (contrasting with other calcium fertilisers that are slower and either raise or lower soil pH).
Winstone Wallboards make horticultural gypsum. This is a fine, off-white crystalline powder. The bulk density of
Winstone's horticultural gypsum is 908 kg/m
3 (loose) and 1172 kg/m
3 (compacted).
Speed of action is increased by reducing particle size. On the other hand, a fine powder is less easily handled by a
mechanical spreader and requires calmer conditions. To meet differing market requirements, Winstone Wallboards produce
two, chemically identical, products - Soil Life a fine ground form (more suited to the domestic market) and Gypsum Natural
a coarser pulverised form (more suited to the commercial market).
For the particle-size distributions of the ground and pulverised products, see the graph below.
This product is of very high purity (93 to 98% calcium sulphate). The table below shows the mineral analysis of major and
minor components of Winstone's horticultural gypsum.
NB: Quantities are stated in ppm unless otherwise specified - indicates data unavailable.
Mineral | Gypsum |
Sulphur | 18% |
Calcium | 23.26% |
| |
Aluminium | 300 |
Antimony | < 4 |
Arsenic | < 1.0 |
Cadmium | < 0.2 |
Chlorine | 1315 |
Cobalt | - |
Copper | 93.8 |
Chromium | - |
Fluoride | 100 |
Iron | 80 |
Lead | < 10.0 |
Magnesium | 93.8 |
Manganese | - |
Mercury | < 0.05 |
Molybdenum | - |
Phosphate | < 19 |
Potassium | 50 |
Selenium | < 0.5 |
Silicon | 800 |
Sodium | 820 |
Tin | < 4 |
Uranium | - |
Vanadium | - |
Zinc | 5 |
See Gypsum Material Safety Data Sheet (PDF 158Kb).
