Levels the uneven ground left from grazing livestock over the winter months.
Improves the cosmetics of paddock.
Tramples the grass crowns which encourage the plant to tiller out. This spread of growth provides better grass cover and yield during the growing season. More grass will also result in better suppression of invasive weeds.
Rolling often follows harrowing, and will push any stones that have risen to the surface back into the ground.
Aerating after rolling will give additional benefits to the health and productivity of your soil.