Healthy soil contains sand, silt and clay particles. Heavy soil contains too many clay particles (the smallest particles of soil) and not enough silt (medium particles) or sand (large particles) to provide plants with the moisture and nutrients they need to thrive and grow. Soils heavy in clay become waterlogged when wet, choking out the supply of oxygen to plant roots. When dry, it compacts easily, preventing roots from penetrating the soil and resisting drainage. Amending the soil properly improves texture and supports plant growth.
Dig or till the soil to a depth of 8 inches and perform a soil test to determine the nutrient and pH level of the soil.
Spread a 2-inch layer of compost, well-rotted manure or other organic matter over the soil and work it in with a garden fork or spade, breaking up any clods of clay. North Carolina State University Extension recommends the addition of 25 to 50 percent organic matter to maintain proper soil.
Add another layer of organic matter (2 inches deep) along with any recommended fertilizer, lime or other additives recommended in the soil summary, and work the mixture into the soil with a garden fork. Turn the soil until the manure or compost is evenly distributed.
Rake the area smooth with a garden rake and plant following the planting depth and spacing for the specific plant.