Aerating Your Lawn
submitted by Don Janssen, Extension Educator
In compacted soil, the soil particles are packed so tightly together that air is driven out, water canít drain through and plant roots canít easily penetrate it. In a lawn, this translates into shallow rooting and poor turf health, and it could eventually result in fertilizer runoff into surface water.
Several types of aeration tools are used to physically modify the soil, either by removing small cores of soil or slicing into it. Research has shown that machines that pull soil cores are more effective. In either case, the closer the tines are spaced, the more soil is affected and the better the results.
Thatch, an accumulation of dead and decomposing grass stems, leaves and roots between the soil surface and the green top growth, is beneficial when itís one half inch thick or less because it allows air and water through but protects grass plants against weather extremes and discourages weed seed germination by shading the soil. Thatch that builds up to over one inch, on the other hand, acts as a barrier to water and air movement. Compacted soils and overwatering encourage thatch formation so often compaction and thatch problems occur together.
Deep aeration -- at least two and one half inches -- gets past the thatch layer and deeper into the soil. If the thatch layer is one and one half inches and the cultivation machine has tines only two inches long, they will barely nick the surface.
The typical bluegrass lawn tends to accumulate thatch more quickly than lawns composed of other types of turfgrass, and two or more aerations a year may be needed for best results. Once the thickness of the thatch layer is reduced to less than an inch, annual aerations may be adequate. Other factors are the type of soil (sandy vs. clay), the degree of soil compaction, the use of the turf, and your goals for the lawn and willingness to commit time, money and effort to maintaining it.
Fall and spring are the best times to aerate because lawns are growing vigorously then and will quickly recover from the process. Avoid aerating when the soil is either very dry or very wet. Tines will not penetrate dry soil, especially dry clay soil, and aerating when the soil is wet may cause unnecessary injury to the turf.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office