Calcium Products - Andrew Hoiberg, Ph.D.

Calcium Products - Andrew Hoiberg, Ph.D.

Andrew Hoiberg, Ph.D.

Andrew Hoiberg, Ph.D.

Gypsum: Source, purity, and particle size matter

The goal of putting a product on your turf is to realize the benefits of that application as soon as possible. Paying for a product that may take years to work just doesn’t make sense. People may argue that gypsum is gypsum, but in reality that’s not true.

There are multiple forms of gypsum: calcium sulfate dihydrate (true gypsum), calcium sulfate hemihydrate (bassanite), calcium sufate anhydrite (anhydrite gypsum), and synthetic gypsum, which is a by-product of scrubbers at coal-fired power plants that force sulfur exhaust gas to combine with calcium carbonate (limestone) to form synthetic gypsum. Within most products on the market that are true gypsum, there can be differences in the purity and particle size distribution, which matters when it comes to getting the most effective product for your turf.

Dissolution of a gypsum product into the soil/water matrix is an extremely important indicator of how the product will react. The two biggest Gypsum Dissolutioncharacteristics that determine how soluble a gypsum product will be are 1) its chemical composition—true dihydrate gypsum will go into solution much quicker than hemihydrate and anhydrite products, and 2) its particle size distribution. If you are comparing two dihydrate gypsum products that have the same purity, it’s true that their chemical makeup is the same; however, if one of the products has much finer particles as a result of its processing, it will go into solution in the soil much faster than the coarser product (which may not ever go fully into solution).

As for synthetic gypsums, there can be undesirable levels of heavy metals in these products depending on which scrubbing system was used and where the product originated. This variability means that you may not be getting the same product each time. You wouldn’t buy a fertilizer that was inconsistent from batch to batch, so why do the same with your gypsum source? There is no one source for synthetic gypsum, so it pays to be wary about how consistent and potentially harmful these products can be to your turf.

SuperCal SO4 (true dihydrate gypsum) comes from one of the purest sources of gypsum on earth and is ground finer than any product on the market prior to pellitization, which results in the highest dissolution rates in the industry. What does all of this mean? It means that SuperCal SO4 goes to work for you as soon as water hits the pellets, and compared to other products that have a wide range of particle sizes, you can put on much less of our product and get the same results. Relying on old application rates that have no scientific basis is not the right way to approach gypsum application. Consulting with our trained staff will get you the right application rate for your situation.

The pelletized nature of SuperCal SO4 makes it much more compatible with turf spreading operations, and it can be mixed with any of your other dry fertilizer products to limit fill ups and labor. Lastly, SuperCal SO4 is 100% organic and is OMRI certified, which fits well into golf course maintenance programs that are trying to be environmentally sensitive to the wildlife and bodies of water found there.









Is it SuperCal 98G or SuperCal SO4?

SuperCal 98G and SuperCal SO4 can often be confused. From their similar names to the similar nature of their appearance, people wonder, how do I know which product I have?

The vinegar test is a simple test you can perform quickly and easily to know whether the product you have is SuperCal 98G or SuperCal SO4.

The acid neutralizing reactions between the carbonate and acid in the vinegar will cause SuperCal 98G to fizz. Since there is no carbonate in SuperCal SO4, it will do nothing.

Combine no more than 1 teaspoon of pellets and a 1/4 teaspoon of vinegar in a reaction proof container with an open top. 



SuperCal 98G is on the left, with its tell-tale fizzing. That is a result of 1 ml of vinegar and 1 tsp of each product. SuperCal SO4 is on the right, no reactions.




SuperCal SO4M on Field Corn Yield


• Planted field Corn (Novartis 2555 Bt) on May 8, 1998 at 33,000 SPA
• 10 acre field
• 5 Replications
• 2 Treatments



Statistical Treatment Comparisons


Project Code: 98-61015

Location: Hollandale, MN

Sponsor: Calcium Products, Inc.

By: Agri-Growth, Inc.



Yield bu/A

SuperCal SO4M

300 lbs/A

156.7 a

Untreated Control


144.3 b


Means followed by the same letter do not significantly differ (P=.05 Duncan's MRT)
Field corn (Novartis 2555 Bt) planted on May 8, 1998 at 33,000 SPA
SuperCal SO4M applied prior to planting
5 replications


SuperCal SO4 with Zn and N on Corn

SuperCal SO4 has been shown to increase nitrogen uptake as sulfur in SuperCal SO4 aids in the nitrification process. Calcium helps to stabilize nitrogen by decreasing volatilization loss. Calcium is essential to the biochemical process of plants to absorb nutrients. Adding SuperCal SO4 to your fertility program will make your expensive nitrogen and zinc work better.

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