Soil Management

This soil combines both excellent water retention characteristics with somewhat unusual and often poor chemical characteristics. In terms of management, the topsoil (A11 and A12 horizons) have excellent chemical and physical characteristics. Management is encouraged to continue current soil management practices. However, management of this soil should consider that only the A11 and A12 horizons are actively contributing to tree growth and crop yield. Whilst the plant available water content of this soil is calculated to be 178 mm, the sodicity in the A2 horizon and aluminium toxicity in the B2 horizons means that root growth and function below the A12 horizon is limited. Consequently, the effective plant available soil moisture is in the order of 80 to 100 mm, whilst the readily available soil moisture is in the order of 30 to 45 mm. In relation to irrigation, the refill point for the A1 horizon is between 32 % (50 kPa) to 28 % (100 kPa) soil moisture. Note that the sodicity and aluminium toxicity issues are a natural feature of these soil and have not been induced by management practices. Due to high subsoil sodicity these soils are not suited to subsoil drainage. Deep ripping for tree establishment is not encouraged as the image of the soil profile indicates this has dragged the less fertile and sodic A2 material into the more productive A11 and A12 horizons, and any relief from compaction resulting from tillage will be short lived as the inherent sodicity will cause the A2 horizon to re-compact once wetup over winter.

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