Primetime Newspapers
By Calvin Finch, PhD, SAWS Conservation Director, and Horticulturist
Week of February 16, 2004
TIME TO AERATE THE LAWN

       If this pretty weather has started your gardening hormones flowing and you are looking for an outlet for your energy, it is time to perform two of the most effective and environmentally appropriate treatments for the lawn—aeration and topdressing.

            Soils that have a significant amount of clay in their make-up are prone to become compacted. Compaction is a state where the air channels are reduced and it is difficult for oxygen and water to penetrate very far into the soil. Anyone who gardens knows that it is necessary that water penetrates to the root system if plants are going to prosper. It is less obvious but just as important that oxygen reaches the roots. Roots die without oxygen.

            There are several types of aerators from which to choose. The best choice is the aerator that has tubes that penetrate the soil and cut plugs of soil, which are deposited on the soil surface. A second option is the aerator that has spikes that penetrate the soil. The problem with this version is that the spikes press the surrounding soil when they penetrate. Some air and water channels are created but the sides of the holes are compacted to a greater degree than the plug-cutting design.

            The typical lawn outside the Loop requires about one hour to aerate; smaller lawns take less time. A machine rented for the full day can accommodate everybody on a street. Taylor Rental (6960 Bandera Rd, 681-2434) is a representative rental store; they charge $24 plus tax for a two-hour rental and $58 plus tax for all day. They also deliver and pick up the machine for an extra charge, depending on the distance from the shop. It takes about one hour to aerate the typical lawn. Some neighborhoods share the machine and rental fee for a weekend

            In preparation to run the aerator, all irrigation heads should be marked with a flag so they are not damaged by running them over with the aerator. If the heads are not flagged, it can be pretty exciting when the irrigation is turned on for the first time. The lawn could resemble Yellowstone National Park with Old Faithful spurting into the air.

            Aeration opens up the soil to allow air and moisture to penetrate to the root zone. For an even greater impact, top-dress the lawn with compost. The material applied one-half inch deep filters into the aeration holes. Air and moisture can still penetrate through the channels in the compost, plus the organic material improves the soil’s capability to hold water and store nutrients.

            Compost retails for about $20--$25/cubic yard. A cubic yard will cover about 640 sq. ft. of lawn. Delivery is about $35 per load (up to 5 cu. yds.). The horticultural supply stores (Keller Material, Fertile Garden Supply, Garden-Ville, and others) offer a top dressing mix that includes both sand and compost, but I recommend you use pure compost rather than the sand mix. Compost is the portion of the top-dressing that improves the soil; sand is filler, it may be appropriate to fill holes in an uneven lawn but, otherwise, use pure compost. The price for both products is about the same.

            Spreading compost is a relatively easy job. The material is light and you do not have to be too fussy about spreading it. I describe it as a “daydream job”. You get some good exercise and do not have to concentrate.

            If you do not have the time or inclination, however, to spread the compost yourself, there is a second option. A company, Oak Hills Top Soil (1-830-249-3575) out of Boerne, offers a unique service. For about $55--$60/cubic yard, they will apply the compost for you. They use a machine that resembles a super-size reverse vacuum cleaner to blow the compost onto the lawn through flexible tubing; it is fast and inexpensive. The company will also do your aeration for you if you prefer.

            The majority of our native soils are prone to compaction and all of them are low on organic material—aeration and top-dressing address the problems.