For many reasons gypsum can be considered to be a farmer’s best friend. Gypsum or CaSO4.2H20 is an excellent source of both Calcium and Sulphur which are essential for both yield and grain quality. However gypsum benefits go much further. As a soil amendment it helps improve the physical properties of soil, such as water retention, permeability, water infiltration, drainage, aeration and structure providing a better environment for the plant roots. The calcium can also displace harmful sodium in the soil, essential to the sustainability of most irrigated soils.
Agricultural gypsum products can come in many forms like:
- Natural Gypsum – Mined
- Recycled from plasterboard – Super Ag Gypsum
- Flue Gas scrubbing on power stations – FGD
- By-product of Fertiliser manufacture – Phospho Gypsum
All of these forms have calcium as calcium and sulphur as sulphate. When comparing any gypsum products you should consider the following items. Gypsum Purity (% of CaSO4.2H20), calcium and/or sulphur content depending on requirements, Solubility, Salts, Heavy metals (such as lead or cadmium), Contaminants (such as paper).
REGYP’s Super Ag Gypsum product is recycled from waste plasterboard into a very pure gypsum source suitable for agriculture. It has a gypsum purity 92%, 17+% sulphur and 23% calcium. These results are averaged over 20 tests spanning 5 years. The measured purity takes into account the 1-2% w/w paper content and the small CaCO3 content <5%. Since REGYP started we have sold over 100,000 tonne of the recycled gypsum with the majority being used in broad acre applications on Canola, Sorghum and pasture.
Benefits of Super Ag Gypsum:
- Higher purity up to 15% more that most NSW mined gypsum sources,
- Its porous granular structure provides more surface area then conventional natural gypsum sources providing increased solubility
- Increased spreading widths (17-19m) over mined sources (11-13m)
Why is the recycled gypsum so soluble? The solubility of gypsum is based on particle size and purity. A higher surface area and higher purity will increase solubility of the gypsum. To get a higher surface area you need a smaller particle size. Recycled gypsum granules do not behave like larger very insoluble natural gypsum crystals. The reason is gypsum that is used in plasterboard manufacture is from one of the most pure sources and it is then milled down to roughly 100% passing 75um (feels like talcum powder) and then when we recycled the plasterboard you have granules that consist of thousands of these 75um particles stuck together. Once these gypsum granules become wet they immediately start going into the soil solution for plant uptake (see NSW Dept Ag, Ag Facts AC10, 2nd Ed).
Super Ag Gypsum is sold from Sydney, Cowra, Brisbane & Melbourne. Please visit www.regyp.com.au for more information on recycled gypsum and its benefits.