There are three main types of hand lawn aerators. There are rotating spike aerators, stake aerators, and manual core aerators. A spike aerator does not work as well as the other two types of aerators since the holes made by them are fairly small, and not too deep. However, they work well in soils that do not have too much clay in them, but have a lot of thatch buildup. Core and stake aerators are great for clay soils. Overtime they strengthen roots to create healthy lawns.
Hand aerators are best when used in hard to reach areas of the lawn, small yellow spots, or for lawns that are very little. Often even people who regularly hire professionals to aerate will have a hand aerator to get the corners, go over troubled areas of the lawn, and do small touch ups. Keep in mind that manual lawn aerators are for touch ups and small areas. Aerating a large lawn by hand will take several days and will not be worth your time since usually you can hire a professional to do it for only to 0.
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The best manual aerators are core aerators, two prongs should be sufficient. The best hand held aerators will have a foot handle for you to push the aerator into the lawn giving you more leverage with your body weight. Given that extra weight, you should to produce decent cores that will last a long time. To lengthen the effect of aerating, you can add peat moss and gypsum just after aeration to your lawn. In clay soils, core aerators are better than a hand spike aerator.
A lawn expert at the University of Georgia, Dr. Robert Carrow compared the effectiveness of different lawn aerators. He found that while spike aerators had little effect, core and plug aerators enabled deeper rooting and water extraction of the grass by 25%. A spike aerator has the most effect in a lawn with little clay content. A manual plug and core aerator works similar to mechanical lawn aerators. Both take cores of soil from the lawn which helps the grass roots to develop and deepen allowing them to find more access to water and other minerals & nutrients essential to a healthy lawn.