A lawn aerator is a machine or garden tool which has been designed for making holes inside soil into which grass can grow. It is especially useful for compacted lawns, since lawn aeration encourages worms, microflora and micro fauna that need oxygen to grow, and improves soil drainage as well. Aeration reduces soil compaction, which disturbs both artificial irrigation and natural rainwater, and makes it extremely difficult for lawn grass to form long roots. Lawn aeration also controls lawn thatch. In small amounts, lawn thatch (a protective layer of organic tissue which moderates lawn temperature and reduces vapor-transpiration) is a good thing, but if the layer is too thick it can reduce watering effectiveness and limit soil oxygenation.
There are several types of lawn aerators available:
- Core aerators (also called plug aerators) - These machines have hollow tines which pull out cores, or plugs, from soil. They reduce soil compaction by creating holes, removing ground soil and leaving the turf core. Aeration allows the holes to remain open for a while, to let fertilizers, air, and water reach the roots. The larger holes that core aerators make can fill up with water during rain showers, so the soil will absorb extra water instead of it running off non-aerated soil. Core aeration is most suitable on heavy clay soils.
- Spike aerators - These machines utilize solid spikes that are wedge shaped to punch holes in the ground. Spike aeration is most suitable for loamy or sandy soils. A spike aerator (also called a slit aerator) creates a shorter lived, much smaller soil perforation, so an operator will have to aerate more frequently than if they're using a core aerator. There are spike aerators available that can slit / spike aerate at the same time as they're spreading fertilizer, lime, or seeds. They can also be towed while the operator mows, making it a combination operation.
- Manual aerators - These machines typically have 2-5 hollow tines which are mounted atop a step bar. The operator pushes downward with one foot on a bar, which forces tines to penetrate the soil. The next step is to pull the step bar handle upward, which extracts soil cores from the ground. The operator repeats this step, and each time any cores that are left inside the tines are pushed out by subsequent ones. A plus for manual aerators is that they are significantly less expensive than powered aerators. In addition, a well-constructed manual aerator can offer selective aeration and ease of use. A minus is that they're significantly slower. It will literally take hours to do a 1/4 acre lot (the size of an average residential lawn). An additional minus is that some machines have tines that are prone to blockage, and that also slows down operation.
- Powered aerators - A powered aerator uses the power generated from ground propulsion in order to drive a number of tines into the ground. Its speed is similar to that of mowing speed, so a large lawn can be aerated in a relatively shorter time period.
Lawn aerator fans are frequently used to give surface aeration to sports fields and golf greens. Healthier turf is created through improved air circulation, as well as remedying heat stress. Hot sun can be overwhelming to turfgrass. If the subsoil of a green reaches a high temperature, the grass roots start to shrink, and that greatly diminishes the putting surface's quality. If a fan is used to lower a green's surface temperature approximately 10 degrees Fahrenheit, it will also lower soil temps by about 4-6 degrees.