Clay soil is heavy, dense and can be dry as hard as a rock if rainfall is scarce. It is the most difficult type of soil to garden in, and it can take a lot of added soil amendments to change the texture of clay soil into rich, friable garden loam. If you add soil amendments every year to your clay soil, the texture eventually will become less dense and more friendly to your garden plants.
Rototill or turn over the clay soil with a garden shovel. Set the tiller at its deepest cultivating depth and slowly run it over the garden area. If digging manually with a shovel, dig down the depth of it and turn it over.
Rake the soil smooth. Break up any large clods of soil and remove large rocks.
Add soil amendments. Add as much of any and all of these amendments as you can get your hands on: shredded autumn leaves, peat moss, compost, vermiculite, perlite, sand, shredded hay or shredded straw. All of these materials will help lighten and open up the texture of clay soil. Spread up to a four-inch layer of these materials on the surface of the soil at a time. Incorporate by rototilling or turning the soil over with a shovel. Rake the soil smooth afterward.
Add additional four-inch layers of soil amendments and then incorporate the material into the soil by rototilling or digging. Working with four-inch layers at a time makes it easier to incorporate them into the soil.
Grow cover crops. Plant clover, oats or winter rye in late summer. After the cover crop has grown for four to six weeks, rototill it into the soil or turn it under with a shovel. During the winter months it will break down and add additional organic matter to the clay soil, helping to lighten its texture.