Over time the use of lawn equipment & the repeated foot traffic of people and pets eliminate pockets of air and moisture between soil particles. This is called soil compaction. This compaction can occur in any type of soil it is worse in clay soils that are composed of tinier particles (like we have here). This compression is compounded in the winter time by periods of excessive snow and rain. Roots make up at least 70% of a grass plant. They take in oxygen and emit carbon dioxide. Spongy permeable soil allows for this air exchange to take place. This is part of the reason why things grow so well in potting soil - lighter particles that have lots of air space in between them. Using a <strong>core aerator (</strong>or sometimes called a<strong> plug aerator)</strong> to take plugs out of the soil helps alleviate compaction. Others - spoon type ( these have 'C' shaped tines) and spike type aerators - simply poke holes in the ground and offer little benefit to the turf and soil.
Why do it in the spring?
Almost anytime that the grass is growing is a good time to aerate. Although we tend to avoid doing aerations during the heat of late summer, springtime works well. The ground tends to be softer and allows the machine to pull longer plugs. Loosened soil combined with spring rains will encourage new and deeper root growth. The direct root contact will make soil amendments and fertilizers more readily utilized. Spring aeration is a great way to prepare your lawn for the rigors of summer heat. For Southern Indiana cool season grasses (blue, rye and fescue) should be aerated from March to mid May (depending on the weather). Warm season grasses (bermuda and zoysia) should be done from early May to late June. Cool season grasses are often aerated in the fall as well. Bermuda & Zoysia should not be aerated in the fall here (this is not the case for areas that are much farther to the south).