Answer: Gypsum (calcium sulfate) is effective in improving a clay soil with poor drainage due to high sodium content. The calcium replaces the sodium on the soil particles and results in an improved soil structure. It is not effective on other clay soils.
If you water is soft (when you wash your hands it feels like you can't easily get the soap to wash off) you could be adding sodium when you water the lawn. Your County Extension Office can assist you with having your soil tested and interpreting the results. Their number is 704-255-5522.
Thanks for the question!
Q&A Library Searching Tips