Question: Can I use gypsum to loosen our tight clay soils? The product label claims it will do that.
Answer: Gypsum doesn’t seem to do a very good job of breaking up normal clay soils. Texas-based university research to back up those claims is sparse, if it exists at all, and my own personal tests in treating a heavy clay soil with gyipsum resulted in absolutely no visible changes in the soil’s structure, nor in its ability to absorb water – after one month and after one year. Incorporating organic matter is still the best way.