Grass thrives in sandy loamy soil and will struggle to get the air and nutrients it requires in clay soil. Because clay particles are so closely compacted it has limited drainage. Although lawns love moisture, they do not tolerate sitting in water. To lighten a heavy clay planting environment takes work and lots of soil amendments.
Til the planting bed to a depth of 8 inches.
Remove the top 4 inches of soil from the bed.
Add 2 to 3 cubic yards of cedar bark mulch for every 1000 square feet of lawn area. Pour it on top of the soil and til it in to a depth of 8 inches. The bark must be mixed in well with the soil, as surface applications will not allow the lower layers of clay to become aerated and they will retain too much moisture. Rake the planting bed so that it is level and there are no hills or valleys.
Take a soil sample to the county cooperative extension office for analysis. There is generally a nominal charge for the test and following the suggestions, based on the test results, can save you time and money.
Add any fertilizer or lime, suggested by the soil test results, and incorporate them into the amended soil to a depth of 8 inches.
Add half the grass seed to the broadcast seeder and sow it by walking in north to south strips, cranking the handle on the broadcaster seeder as you walk. Add the remaining seed to the seeder and sow it in an east to west pattern.
Rake the area lightly so that the seeds are just barely covered with soil.
Pack the planting area with the roller.
Water the planting area with the fine mist setting. Water twice a day until the seeds germinate.