Agricultural gypsum sources can vary greatly in their quality and respective Calcium and Sulphur contents. When comparing gypsum options for your application please ensure you investigate the properties of each product accurately to ensure you get the desired result without paying too much.
The majority of our Ag gypsum products that we sell (natural & recycled) contain 17% Sulphur (S) and 22% Calcium (Ca) making them some of the most pure gypsum products available in Australia.
If you need to do calculations to compare the landed cost of various Gypsum sources delivered to your site, the office can email you a spreadsheet which is setup for the task.
Remember that Ag lime, dolomite and calcium silicate aren’t gypsum and they have different properties to gypsum and change your soil properties differently. If unsure on which product to use please contact your local agronomist or our office.
Gypsum is Graded generally into the following grades:
- Grade 1 Gypsum – contains >15% Sulphur (S) and >19% Calcium (Ca)
- Grade 2 Gypsum – contains >12.5% Sulphur (S) and >15.5% Calcium (Ca)
- Grade 3 Gypsum – contains >10% Sulphur (S) and >12.5% Calcium (Ca)
The below snippet allows for you to compare what you are planning to use on your farming operations versus other options.
Gypsums Ain’t Gypsums
Pacific Fertiliser and REGYP sells over 100,000 tonne of high quality gypsum every year with a rough split of 50% natural and 50% recycled. If we could produce more recycled gypsum we would sell more, as people realise the benefits of a lower cost, high analysis product with a low salt content.
We have undertaken laboratory studies to bench mark different gypsum products from different mines and processing plants to ascertain their quality and compare their properties from the lab results. See the results from the study where we used a NSW Ag Facts method to test gypsum solubility. Study link http://pacificfertiliser.com/gypsum-quality-comparison-report-2017/1835/ . Please also find attached a Gypsum Cost Comparison spreadsheet where you can compare your various gypsum quotes from various suppliers to assist you with an apples with apples decision.
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 Gypsum
- By-product of Fertiliser manufacture – Phospho Gypsum (from the old super plants – not available anymore)
All of these variants of CaSO4.2H20 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 clay & 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 90+%, 17% sulphur and 22+% calcium. These results are averaged over 40 tests spanning 9 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 200,000 tonne of the recycled gypsum with the majority being used in broad acre applications on canola, sorghum, cotton and pasture. However it have been used on many other crops such as potatoes, corn, cane and numerous vegetable & horticultural applications.
Benefits of Super Ag Gypsum:
- Higher purity up to 15% more than most NSW mined gypsum sources,
- Its porous granular structure provides more surface area then conventional natural gypsum sources providing increased solubility
- Low salt content
- 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 (ultra fine gypsum which 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).