Aerating
Aeration involves perforating the soil with small holes to allow air, water and nutrients to penetrate the grass roots. This helps the roots grow deeply and produce a stronger, more vigorous lawn. The main reason for aerating is to alleviate soil compaction.
Overseeding
Over time, grass does get old and needs to be replaced. Worn-out lawns invite weeds. Overseeding is a fast, inexpensive way to help bring your lawn back to its lush, green, healthy self without tearing everything out and starting over. It's also a great way to introduce a new type of grass. In Western Iowa and Eastern Nebraska, the best time to overseed your lawn is in the fall. The soil is still warm but the air is cooler. There are fewer weeds for new grass to compete against.