Soil Quality
Fact Sheets - Seedbed Soil Structure Decline
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Summary
Surface soil structure decline generally results in one of two things – hardsetting or crusting. A surface crust is typically less than 10 mm thick and when dry can normally be lifted off the loose soil below (Mullins et al. 1990).
Crusting forces the seedling to exert more energy to break through to the surface thus weakening it. A surface crust can also form a barrier reducing water infiltration.
Soil structure breakdown caused by rapid wetting can lead to hardsetting. The unstable soil structure once wet, collapses and then shrinks as it dries. This leads to a ‘massive’ soil layer with little or no cracks and greatly reduced pore space (Needham et al. 1998). This hardset ‘massive’ structure is associated with poor infiltration, low water holding capacity and a high soil strength (Figure 1). In many instances, this causes patchy establishment and poor crop & pasture growth.
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