Calcium Products - Anhydrite vs Dyhydrite--is all gypsum the same?
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Anhydrite vs Dyhydrite--is all gypsum the same?


This article is reprinted from, the Professional Turf Division of Calcium Products. It is writen by Brian Milam.

As a turf professional it is very important to understand what exactly gypsum is, what the differences are between Anhydrite and Dyhydrite forms of gypsum and then the benefits for using the correct form of gypsum.

First of all, let us explore the 2 main types of gypsum. There is anhydrite gypsum and there is dyhydrite gypsum. Both forms of gypsum are a Calcium Sulfate (CaSO4) but only Dyhydrite forms of gypsum seem to be the most effective. Why might this be the case?

Before I explain why a dyhydrite is more effective let’s try and understand what gypsum looks like to begin with. Gypsum is a naturally occurring mineral that is in a crystalline form that contains Calcium and Sulfur in sulfate form.  In an anhydrite form there is no water associated within the crystals, just Ca and S. In the dyhydrite forms there are 2 molecules of water attached to the Ca and S and it is these water molecules that make all the difference in the world.

Anhydrite Gypsum --> CaSo4

Dyhydrite Gypsum --> CaSo4 – 2H2O

Dyhydrite is more effective because it is more water soluble and the more soluble a mineral can be the more nutrient uptake can occur with the plant.  When gypsum becomes soluble in water the calcium separates from the sulfur and the faster that separation can occur, the more nutrients can become available to the plants. In anhydrite forms of gypsum this separation happens at a much slower pace and because of how slow it takes the less effective the product is a reducing compaction layers, leaching potential and sodium remediation.

Benefits of Gypsum use in the turf grass industry:

  • Effective in leaching of harmful salts and impurities from the root zone
  • Enhances soil structure
  • Reduces the layers of compaction
  • Increases Water Infiltration Rates
  • Increases amount of water available to the plant
  • Provides pockets in the soil to allow for deeper root growth and expansion
  • Provides an organic source of calcium which creates a stronger, healthier plant
  • Will not affect pH of the soil

In conclusion, there are many different labels under which gypsum is being sold and marketed. The only way to ensure you are going to be getting an effective product is to source one out that is derived from CaSO4-2H20.  It is also very important when looking at where the gypsum is derived from you look at the purity of the materials. Excellent grade materials will have a purity exceeding 92%. 


Dyhydrite Gypsum sources

Additional Info

  • Article Reference:: Calcium Products, Inc.
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