In most cases, after sowing, a lawn will look good for a few years. Over time, however, the soil compacts, and water, nutrients and oxygen can no longer reach the grass roots properly. Soil compaction is a process caused by traffic, lawn mowing, but also by water. The solution is aeration which is a totally different process from scarification.
Lawn aeration is often confused with scarification, but they are completely different operations and performed with different machines. Both operations are necessary to have a healthy lawn and do not replace, nor exclude each other. Aeration involves the creation of holes in the surface of the lawn by extracting plugs of soil with a diameter of 1.5 cm and a length of about 7 cm. Over time, these gaps tend to be filled by “collapsing” soil around them, so the ground will become loose.
Creating these gaps and loosening the soil allows the plant’s root system to grow, and water, nutrients and especially oxygen will easily penetrate the roots. There is a big difference between the method of creating gaps by digging holes and the method of inserting a solid metal rod into the ground. The latter only makes the ground around the created hole even more compact.
The aeration operation is generally performed in autumn and spring, for great organic fertilizer products see https://therichlawncompany.com/.