Clay soil is very compact since it is made up of the smallest soil particles. This means it holds onto nutrients, which is good for plants, but it also means it holds onto water, which is bad for drainage. The ideal soil is loam, an equal mixture of silt, clay, organic material and sand. Loosening up clay soil by adding organic material will improve its aeration and drainage, but it takes a bit of time and work.
Measure the square footage of the area in your yard in which you wish to loosen up the clay soil. Multiply the space's length and width to determine the square footage.
Add 4 inches of compost or manure to the clay soil for every square foot.
Work the compost or manure into the clay soil to a depth of 6 inches with a till. Break up large hunks of clay as you work the compost or manure into the soil.
Plant a cover crop over the area, such as white potatoes. The cover crop's roots will loosen up the clay soil as they spread. Once the cover crop dies back, work it into the soil to add more organic material. Plant a cover crop with deep roots to loosen up clay soil as deeply as possible.
Add mulch such as straw over the top of clay soil. The mulch will break down and add more organic material into the soil, thus loosening up the clay.