The scarification process is the removal of thatch build-up in the turf surface.
Thatch is the layer of vegetative material above the soil but below the leaf. Nearly all lawns require this process at some stage of their life. Different varieties have different rates of thatch build-up with the green couch family (cynodon spp) having the greatest propensity to thatch and blue couch (digitaria) the least.
A scarifying machine works by having vertical blades rotating at high speed. These blades tease and thin out the dead material from the base of the lawn.