Over time the soil that the lawn grows on can become compacted due to a number of reasons such as use for sports, walking, vehicles, parking and children playing. This soil compaction can have a negative effect on your lawn.
Not enough air or water: Compacted soil leads to a reduced amount of air held in the soil, restricted air flow and reduced water infiltration into the soil. If air and water can’t get down to the roots, you won’t have the thick, full lawn you want.
Not enough nutrients: If air and water can’t get down to the roots, neither can key nutrients your lawn needs to reach its maximum potential. When your lawn doesn’t get the food it needs, it also puts it at higher risk from drought and other environmental stresses.
Too much thatch: There are other factors besides soil compaction that may give you a reason to aerate your lawn. If your lawn contains a considerable buildup of thatch (the unsightly organic debris that builds up faster than it can be broken down) then you must aerate to help break it down. Aeration pulls soil cores up to the surface and brings microorganisms with them. These microorganisms break down the layer of thatch and return nutrients to the soil. Lawn aeration may also be necessary on heavy clay soils to help soil air circulation and water filtration.