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Why do lawns need to be aerated?

Breathe In, Breathe Out: Lawn Aeration
A tractor aerates a golf course, leaving behind plugs of soil in its path.
A tractor aerates a golf course, leaving behind plugs of soil in its path.
© Braun

­As any landscape specia­list will tell you, mole people simply don't pose a risk to the health of your lawn, but soil compacting does. This situation is exactly what it sounds like: Over time, foot and vehicle traffic mash down the soil in your lawn, compacting all the particles. Even regular mowing takes a toll, and poor drainage and wet conditions make matters ever worse. This situation poses a problem to lawns because compacted soil has far fewer air-filled pore spaces. Plan­ts depend on those pore spaces to supply roots with much-needed oxygen. Compacted soil prevents roots from expanding, interferes with water filtration and disrupts nutrient uptake.

Lawn aeration helps alleviate this situation by creating holes in the ground, which allow air back down into the soil and create room for compacted soil to collapse back into a looser particle arrangement. In a way, lawn aeration is much like perforating a tough cut of meat prior to marinating it. The holes you jab in a flank steak better allow the juicy marinade to seep into the meat. Likewise, the holes in a freshly aerated lawn allow air back into the soil.

When the soil is properly aerated, there's more room for roots to expand and for helpful microorganisms to go about their business. Rain and irrigation water is able to soak farther into the ground, and there's less danger of runoff from such potentially harmful substances as fertilizer, pesticide and gray water. Of course, the fact that aeration is good for your lawn doesn't mean you need to do it every day.

First, there's the amount of traffic to consider. A yard that regularly plays host to touch football games will naturally experience much more compaction than a yard that only gets cat and chipmunk traffic. Second, lawns are composed of different varieties of grass that experience different growth cycles. Lawn aeration should take place during high growth periods, which allows the lawn to recover and take advantage of all the new space at the fastest possible rate. Warm season grasses, such as Bermuda grass, are warm season growers and should be aerated in the spring. Cool season growers, such as bluegrass, are best aerated in the late summer or early fall. Therefore, the third factor to consider is climate since local conditions will dictate when your particular grass will be ripe for aeration.

Freshly sodden yards won't require aeration during their first year, but after that, estimates vary depending on the above factors, as well the kind of soil you have. Clay soil compacts more easily and benefits from biannual aeration, while sandy soil compacts at a slower rate and only needs one aeration per year. Gardens also benefit from aeration, though this is typically accomplished through simple tilling and turning of the soil

Ready to grab a spike and join in all the lawn violence? On the next page, we'll look at the equipment and methods involved in lawn aeration.