My plan for a 2014 field study using gypsum

2014 Gypsum Studies

Truth be known, I am a fan of gypsum. I have written about it and studied marketing pieces, research data and scientific articles. But at the end of the day, I like what it does to the soil.

My current passion is improving soil health. If I were to write a recommendation for building the perfect soil, my ingredients would include gypsum, compost, cover crops, residue management and decomposition, vertical tillage and changing the biological makeup of the soil.

Gypsum field study
Gypsum field study

As an agronomist, I have always been a bit concerned that I don’t see much good data on how treatments affect soil’s biological, chemical and physical characteristics. I am about to change that by taking measurements that are sensitive to these changes.

I have been using gypsum for 10 years now and have seen how it changes soil tilth when used alone and in combination with other practices. This year, I am testing different rates of gypsum applied by soil type, different rates of pelletized gypsum and synthetic gypsum applied with a polymer. This yet unnamed polymer is supposed to keep calcium and sulfate available in the soluble water phase for several months during the growing season.

Last summer I did a polymer pilot study and applied 400 lbs. per acre of untreated gypsum to 5 acres and then applied 400 lbs. per acre of treated gypsum to 5 acres. I sampled the soil before treatment and then about 65 days later and after 8 to 10 inches of rainfall.

  • With polymer there was an increase in soluble calcium (43 to 90 ppm) and exchangeable calcium, (3110 to 4162 ppm) compared to the untreated block
  • With polymer there was an increase in sulfate (50.4 to 105.6 ppm) after gypsum was applied compared to the untreated block

This year I am looking more in depth at calcium and sulfate. We are pulling soil samples at 0-3 inches and 3-6 inches and measuring exchangeable and soluble calcium and soluble sulfate in the soil. We are pulling soil samples once before application and twice afterwards. We are also looking at plants and their ability to take up more available calcium and sulfate from the soil. Plant uptake is a direct measure of more available nutrients.

The objective here is to measure the amount of exchangeable and soluble calcium and sulfate in the soil and plant tissue. We are not measuring tilth directly because it takes a number of years to improve tilth and this is only a one year study.

If all goes well, I will write about the results this fall or winter. As with any science project answering a few questions, additional unanswered questions will always be unearthed.

Dr. Davidson posts articles on soil health and management related subjects. If you have suggestions for topics or questions, feel free to contact him at or call 402-649-5919.