Answer: The first thing to do is to run some basic soil tests to check fertility and also soil pH. Then fertilize and/or lime according to the test results. There is no way to judge how much is needed without testing, and it is never good to over fertilize or over lime. That would be a solid step toward improving your lawn.
Another step to consider is core aeration (a core aerator pulls out plugs of soil, it is not the same as a spike aerator that just pokes holes) combined with a top dressing of good quality compost. This can help reduce compaction and aid infiltration of water and nutrients.
Your local Purdue extension should be able to help you with the tests and interpreting the results as well as developing an ongoing care program suited to your yard. In the meantime you may find some of the following Purdue lawn care information helpful. You may need to cut and paste the complete url into your browser to make it work correctly.
Good luck with your lawn this summer!
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