Aeration is important to maintain a healthy lawn. Over time the soil below your lawn becomes compacted due to walking, playing, mowing and watering, which can halt lawn growth. Aeration involves making 2-3 inch deep holes in the soil so that air, water, and nutrient exchange will be improved between the roots. We recommend aerating your lawn once a year as a standard, but if your lawn is used more often for activities that cause compaction, more than one aeration may be needed to keep your lawn healthy. The best time to aerate in Iowa is during spring and fall.