Hollow Tine Aerator
Hollow tining or coring is the removal of cores from the lawn and is a very good way to aerate AND relieve compaction. It will also improve drying which is beneficial in the autumn when the rains start particularly if you have a moss problem. It's not advised in the spring because you need to conserve moisture as the sun gets stronger!
Extremely sandy soils may not benefit so much and for these you just need the rolling lawn aerator and aerator sandals discussed previously. Heavy clay soils would benefit the most but due to the sticky nature of the soil can clog the tines and not eject so defeating the object. Good quality or heavy use lawns with soils between these two extremes will benefit from core aerating with hollow tines every year in the autumn. For other lawns every two to three years would be fine.
Coring equipment for lawns revolves primarily around two types of aerator. There is the hand held hollow tine fork which is a bit like a garden fork but with hollow tubes rather than spikes. Then there are petrol powered hollow tine aerators. The ‘lawn variety’ has several rotating drums totalling 30 plus corers. They won’t go much deeper than about 2” but will do a good job. They’re expensive but luckily are readily available at hire shops and can often be fitted with solid spikes if preferred.
The ‘sports turf’ variety has a cam action that punches the spikes or corers into the lawn. These penetrate deeper, have a greater density and less surface disruption. The downside is that they are hard to turn on lawns and will do serious (and dangerous) bouncing on any rocks or rubble in your lawn. These are perfect for ornamental lawns with a fairly stone free soil profile.