Soil Management

Despite evidence of surface compaction and extreme soil density in the A22c horizon, this soil profile holds a considerable amount of plant available soil water and readily available moisture. In relation to irrigation, the refill point for the A1 horizon is between 31% (50 kPa) to 24 % (100 kPa) soil moisture. Ripping the B21 horizon will be important for tree establishment. The health / quality of the A11 horizon is moderate to low, as indicated by the low drainable porosity, and only moderate organic carbon. These values indicate the upper most soil layer is compact, lacking in macroporosity and will possibly have poor aeration status for root function. The low CEC of the A1 and A2 horizons indicates the topsoil has limited ability to retain and supply nutrients, whilst nutrient which are leached below the A22c are likely to be retained in the B2 horizon. Management should consider approaches to improve the carbon levels and structure of the A1 horizon including; greater application of plant residues to the tree mound, use of living mulches, grass clippings, mulches and composts. The A22c horizon was noted to be extremely dense at 2.02 g/cm3, this is likely to be a natural feature of this soil associated with high soil sodicity and has not been induced by management practices. Deep ripping is not encouraged as it risks dragging the less fertile and sodic A2 material into the more productive A11 and A12 horizons. In addition, any reduction in compaction resulting from ripping will be short lived (possibly less than 12 months) as the inherent sodicity will cause the A2 to re-compact once wet-up over winter. Due to high subsoil sodicity these soils are not suited to subsoil drainage.

More Soil Information: