Product Info - Gypsum New Zealand

By: Gypsum  06-Dec-2011
Keywords: Calcium Sulphate

What is Gypsum?

Gypsum is known to chemists as calcium sulphate di-hydrate (CaSO4 - 2H2O).

What do we use Gypsum for?

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).

Technical Specifications

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


(loose) and 1172 kg/m


(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.










< 4 


< 1.0 


< 0.2 












< 10.0 





< 0.05 



< 19 




< 0.5 






< 4 




Keywords: Calcium Sulphate

Other products and services from Gypsum


Applying Gypsum - Gypsum New Zealand

Gypsum relies upon rainfall to solubilise it and so move it into the soil profile where it has its effect, it is therefore best applied in early spring or after harvest when rainfall can do its work. Gypsum is also useful as a carrier to assist in the uniform application of small quantities of zinc, manganese, boron and the other trace elements.


Waterborne Application - Gypsum New Zealand

Their physical condition is degraded by tillage, the use of machinery etc; their chemical condition is degraded by the crop's removal of minerals, by leaching etc; and their moisture content is depleted by transpiration - plants remove water from the soil at a rate proportional to their growth.


Subsoil Compaction Affects Wheat / Barley Yield

Soil acidification is an inevitable consequence of intensive cropping with silage crops having greater acidifying effects than grain crops due to the removal of the basic cations contained in the straw. Normal practice is to apply lime and to cultivate this into the topsoil to achieve appropriate pH and calcium levels based on annual soil tests made prior to planting.


Subsoil Compaction Affects Maize Yield

While management of just the 0-20 cm topsoil layer is sufficient to meet the crop's mineral nutrient requirements, to provide it with sufficient water in summer requires either regular irrigation or root zone access to water contained in a much deeper soil profile - roughly from 0-100 cm.


Effect of Dairying on Pasture Soils

The pasture growth reduction can be offset to some extent by increased fertiliser usage but this tends to decrease soil pH and to increase nutrient loss so they are not remedial in their effects - more of a 'band-aid' approach. In recent years we have seen good growth in the New Zealand dairy industry associated with a rise in dairy cow numbers along with higher stocking rates and increased use of nitrogen fertilisers.