Clay soil is the plague of many home gardeners. Thick, clay soil is hard to break apart, retains a large amount of water and often becomes compacted when pressure is put upon it. Clay soil is often adjusted with the application of organic material such as silt soil, peat and wood chips. Gypsum changes the structure of the clay soil by breaking up large clumps, removes sodium from the soil by replacing it with calcium and does not affect soil acidity in the process.
Break up the clay soil with a shovel or run over the area with a rototiller. Run the rototiller in two directions over the soil to thoroughly break apart the soil.
Measure the area of the garden in feet and write it down on a piece of paper. A garden requires 40 pounds of gypsum for every 1,000 square feet of soil.
Pour the gypsum over the tilled area of the garden, and run the rototiller over it again to mix the gypsum into the soil. Pour a generous amount of water into the soil to activate the gypsum.
Repeat this process at the beginning of every planting season. Gypsum application will work after several applications, depending on the density of the clay in the soil.