All revegetation operations require some form of soil disturbance to prepare the site to receive seeds or plants. How much disturbance is carried out depends on the technique and the soil type. The advantages of soil disturbance are that it can create an easier path for roots to penetrate and that it makes it easier to plant. The main disadvantages are that it can stimulate weed germination and cause moisture to be lost from the soil.
Some form of weed control followed by light cultivation can be effective in encouraging natural regeneration. When seeds fall from the trees they will germinate faster if they land on mineral earth in a weed free environment. Be careful not to disturb the roots of the parent tree by cultivating too deeply.
Sandy soils usually require little ground preparation. This site in Western Australia has been scalped and prepared with a Chatfield planter.
For direct seeding and tubestock planting, it is common to rip the soil with a single tyne ripper, to a depth of at least 300mm (and up to 1.2m in forestry plantings). When carried out in relatively dry soil this has the effect of shattering the soil to increase water infiltration and allow easier root penetration. It also creates a looser soil surface making it easier to plant tubestock. It is important when deep ripping to allow the soil time to settle so as not to leave air pockets. Ripping is particularly effective in areas where a cultivation pan has developed below the level of previous cropping operations. Ripping should be avoided in soils that crack deeply when dry. In these soils weed control is often enough to create a soft friable soil for planting: a technique known as chemical fallow. Ripping is often not necessary in sandy soils.
Ripping is often combined with cultivation, mounding or both to create a fine tilth in the surface soil. This makes planting easier and encourages good root development. Mounds create a large volume of soft soil which encourages rapid early growth. As such it is commonly used in commercial forestry plantations, where ripping and mounding is carried out in one pass with a large plough drawn by a bulldozer. For small plantings a set of opposed discs drawn by a tractor or even a hand-pushed rotary hoe can create a soft surface. Greening Australia trials in northern NSW have shown that in summer rainfall areas, mounds can be detrimental to survival, as they tend to dry out quickly over summer.
Intensive research in Western Australia has developed a new ripper designed to adapt to different site conditions and to provide a significant improvement over conventional single-tyne rippers. You can read more about this ripper on Nature Base.