Now is the Time to Aerate, if you Must

Core aeration leaves plugs of soil and turf on the surface, where they will quickly break down back into the lawn.

Folks in the northern tier of the United States and across Canada seem to be genetically programmed to perform two lawn tasks in the fall no matter what: apply lime and aerate the soil. And while that’s an overexaggeration and not everyone does it, a surprising number of people are at least curious about it.

The application of limestone to the soil has traditionally been done in the fall to raise the pH in the wide swaths of North America where the soil is inherently acidic. Grass likes a pH of 6.5-7 and the addition of limestone is the most efficient way to modify the soil pH for the most optimum growth of the plants.

We now know that it’s important to apply the right kind of limestone, or you’ll run the risk of encouraging weed growth. Check back here in the next couple of for a deeper explanation of why high-calcium limestone is important in many situations.

For today, we’ll focus on the act of aeration — which in its simplest terms is defined as the act of adding air to the soil. By adding air, you’re allowing water, fertilizer and other “top-dressed” amendments such as compost to get down to the roots faster. You’re also creating better conditions for soil organisms such as worms and other microscopic creatures that are essential in a natural, organic system of lawn care. Healthy soil will promote healthy grass and weed reduction so you can avoid applications of pesticides such as weed killers.

NOTE: Whichever form of aeration you choose, you should aerate prior to overseeding or top-dressing of any material if possible. In the North, fall aeration is preferred because too many weed seeds are flying around in the spring, which can contribute to a weed problem on the lawn later in the summer.

Core Aeration — This technique involves “pulling cores” of soil and turf out of the lawn and laying them on the surface of the lawn. The resulting holes can be left alone to fill back in over time (usually very quickly), or they can be filled with amendments such as compost, sand, fertilizer, stone dust, gypsum or whatever is called for in the soil test. Hand tools are available for small areas, but most folks either hire a professional or rent a gasoline-powered machine, pictured above, for a few hours, which usually costs about $30 for a half day. If you’re doing it yourself, make two passes across the lawn, one in each direction.

The power aerator itself isn’t much bigger than an average walk-behind mower, but significantly greater physical strength is required to run an aerator, especially if your lawn is sloped at all. You’ll also want to mark the location of any sprinkler heads on your lawn, or anything else that is buried closer than four inches from the surface of the soil. The hollow core tines on this machine are sharp and can do a lot of damage.

Deep Tine Aeration — Typically done by professionals with the proper equipment, deep-tine aeration — which can involve either coring, spiking or drilling — is similar to core aeration described above. In this technique, as the name would suggest, the tines go deep into the ground, often up to 24 inches. This can be really useful in heavy clay soils, or in areas with major compaction from foot traffic or years of neglect. Be careful when using deep-tine equipment to avoid irrigation lines, underground utilities. Most homeowners don’t go to this length on their lawns, but in extreme cases it can be worth the price — which will probably be five to seven times the cost of mowing your lawn.

Sandal Aeration — We don’t recommend this at all. The spikes on the bottom of the sandals do poke holes, but since no soil is removed from the hole, the soil on either side of the spike is actually compacted to a greater degree.

Natural Aeration — The good news is that lawns treated with organic techniques and amendments, in time, will not need mechanical aeration unless the foot traffic is severe — think golf course, playing field, or a back lawn that is heavily trampled by children. In natural systems, aeration occurs naturally when earth worms and the other microscopic creatures crawl around in the soil. Leaving the grass clippings on the lawn and the occasional top-dressing of compost will also help with natural aeration. Applications of organic fertilizers, which are soil foods rather than plant foods, will also increase the microbial content of the soil and therefore aid in natural aeration.

Numerous liquid products labels as “soil aerators” are now found in the marketplace. Many, quite frankly, are suspect products, seemingly designed to capitalize on people’s aversion to power equipment — especially rugged aerators. Some products do work well, however. Here is one worth looking at from Outside Pride, http://www.outsidepride.com/lawn-aerators/liquid-lawn-aerator.html.