If the soil in your lawn clumps together and your grass is brown and patchy, you likely have clay soil. Hard clay soil can cause serious drainage issues in your lawn, especially if your yard is flat without any slope. Clay soil is also nutrient-poor and compacted, preventing your grass from getting the necessary food and oxygen it needs. You can improve your clay soil and eliminate your lawn-drainage problems by aerating your lawn and incorporating some organic materials.
Aerate your lawn using a punch-core aerator. Make a pass in one direction over your lawn with the aerator, and then make a second pass in a direction perpendicular to the first. Aerate your lawn when the soil is moist.
Spread a 2- to 3-inch layer of organic compost or sphagnum peat moss on top of your lawn. Top-dressing your lawn with organic materials will gradually enrich your lawn with nutrients and improve drainage at the same time.
Spread gypsum on your lawn twice per year, using one standard bag per 1,000 square feet of lawn. Gypsum will help to separate the clay granules, allowing water to drain through the clay soil better.
Till your clay soil with a rototiller or pitchfork to loosen up the hard clumps when planting a garden or flower bed in your lawn. Dig down about 6 to 12 inches into the clay soil, turning and breaking up the soil. Then, mix sphagnum peat moss or organic compost into the top 6-inch layer of the soil.
Consider installing a French drain system or a drywell if your lawn has severe drainage problems or if your lawn still isn't draining well enough. Grading may also be necessary if your lawn is soggy and does not have an adequate slope for water runoff in addition to the clay soil.