Clay soil presents a problem for gardeners as it lacks the proper nutrients and the proper drainage to successfully grow a garden. Advertisers bill gypsum as a solution for these problems. This claim is not true, as gypsum does not always change the structure and nutrient content of soil. If your clay soil has high salt content, however, gypsum can remove the salt by turning it into calcium. In order to increase fertility of salty, clay soil, knowledge of how to apply gypsum to clay will help you create the right environment for your plants.
Test your soil with a soil test kit or by bringing a sample to your local extension office in a container. The tests will reveal any nutrient deficiencies and the salinity of your soil. If your salinity is high you will need to add gypsum to your soil.
Lay down 2 inches of peat or compost and work it 4 to 6 inches into the soil. This will loosen up the clay and prepare it for the gypsum.
Lay down 20 pounds of gypsum per 100 square feet. Mix it into the soil down to 4 to 6 inches with a spade.
Water the soil deeply. This will ensure that the gypsum settles in properly and that there are no air holes in the soil.