Clay soil is the bane of gardeners all over the world. It causes plants to develop root rot, starves plants of oxygen and makes it hard for young plants to grow. But clay soil can be tilled and amended with organic material to make it more suitable for growth. However, be careful when tilling clay soil as it can be temperamental, especially when wet. And don't expect results overnight. It takes several years of amendments to permanently change the composition of clay soil.
Spread organic matter over the soil (3 to 4 inches of a mixture of peat moss and well-aged compost are standard for most heavy-clay soils).
Till the soil to a depth of 1 foot. Till small areas with a spade. Larger areas will require a rototiller.
Till the soil again to a depth of 1 foot. This time work at a 90-degree angle to the first direction you went in. To amend clay soil for planting, many gardeners add a 1- to 2-inch layer of coarse builder's sand to the soil before tilling a second time.