Question
Yikes! I just read your answer to Debbie about grass not growing in low areas with clay soil. You said the worst thing you can do is put loose soil on top of hard soil.  When we moved in 2 years ago, that is exactly what the landscapers did - claiming the ground was too hard to till! (It is doable, but difficult.) They put down about 2-3 inches of a topsoil/planter's mix and then sod. We already seem to have a lot of thatch, some of the grass seems to get seedheads quickly, and it is brown and dying off in the low spots.  We really can't afford to rip the sod out and start over. We had it aerated this spring, but I wonder if it's too late for that.  I'm hoping there is a short-term solution to keep the low spots from dying and a longer-term solution to impove the overall health of the lawn.  I'm thinking perhaps  having it aerated each spring and fall and raking in a think layer of top-soil?  I contacted the local extension and all they said was we should have done it right in the first place! Of course, but is there anything we can do now?  Thank you for your suggestions!  

Answer
Hi Tracy, The best solution would be to rent a sod cutter, remove the sod, till the soil mix into the clay, level the ground and replace the sod.  That said, this is what I would probably do...
First, in the low areas, spread about 1/2 - 1" of clay.  It needs to be dry to spread evenly.
Next, aerate the lawn again.  This will drive some of the clay into your rootzone. Aerate thoroughly.
Then overseed or sprig your type of grass at the appropriate time.
Next, always bag the grass in the low areas, we want nothing to slow the natural drying process.
Also, warm season grasses can be overseeded with annual ryegrass during the winter, this will help dry the soil.
Then fertilize the lawn with 0-20-20 fertilizer at the rate of 10 lbs. per 1000 square feet, this will help strengthen the root system.
Make sure your pH is at 6.5.
Water thoroughly, deeply, but infrequently.
You may also have some fungal problems in wet areas, so you may have to apply a fungicide to fix that.  Take a sample and some pictures by your local garden center for a positive identification.
You may need to repeat the clay and aeration steps a couple of times until the soil is raised enough to prevent puddling.  Jim