Paul James, host of HGTV's Gardening by the Yard, explains the benefits of aerating and liming your lawn. Most lawns get a fair of amount of traffic, especially if children use them. Such traffic -- as well as the act of mowing -- results in compaction of the soil. Compaction ultimately hinders a plant's ability to grow because it reduces the soil's capacity to hold water and oxygen. Fortunately, aerating solves the problem. Aerating may be accomplished in several ways. A heavy-duty spading fork may be stabbed into the soil and gently rocked back and forth to break up compacted dirt, although this method is time-consuming. A second method is to wear lawn-aerating spikes, and the third and most effective method is to run a core cultivator (figure A), or power aerator over the lawn. Most rental companies offer these tools at half-day and full-day rates. Sharing the aerator with neighbors can help reduce the cost. It's best to run an aerator when the soil is slightly moist: the aerator won't penetrate as deeply into dry soil. Most aerators run on gasoline and are fairly easy to operate. Simply pull the choke, give the starter rope a few pulls, and release the choke once the engine starts running. Engage the core cutters, and work your way over the lawn. If your lawn is quite compacted, make more than one pass. If possible, go north and south the first pass, east and west the second pass. Take your time, and let the machine do the work. After the aeration is complete, you'll see hundreds of soil cores on the lawn. As the core cultivators pierce the ground, they remove a core of soil and leave a hole. These holes enable water, air and nutrients to penetrate deep into the grass's root zone, reducing soil compaction. The cores can be raked up or left on the lawn; they'll decompose within a couple of weeks. After aerating, fertilize and water the lawn. If you have plenty of compost, sift it and top-dress the lawn with it to add organic matter to the soil. The frequency of aeration depends on the amount of traffic the lawn gets. In most cases, every three years or so is sufficient, but for heavy-traffic yards, once a year is appropriate. If the lawn has been neglected for several years, it might be wise to aerate it several times in one year to rejuvenate the soil. The best time of year to aerate is when grass is actively growing, which means fall for cool-season grasses and late spring for warm-season grasses. The grass will quickly cover the holes. In much of the United States, especially east of the Mississippi and in the Pacific Northwest, soils are naturally acidic. Virtually all of the common turf grasses used in lawns prefer a neutral pH, which is why homeowners typically apply limestone to lawns. Limestone products, whether calcitic or dolomitic, are available in bags and are easy to apply with a drop or a broadcast spreader (figure B)<#IMG RIGHT>. The only way to know for certain whether the soil needs lime is to have the pH tested. This can be done by sending a soil sample to a lab or by using a home test kit, which will provide a fairly reliable reading. How much limestone should be applied? If the lawn is slightly acidic, apply 5 pounds per 100 square feet in the fall, then have the soil's pH tested again the following spring. Apply more limestone if necessary.
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