Soil Management

The key to managing this soil is recognising that the A2 and B2 horizons are making little contribution to the supply of water and nutrients to the trees. The subsoil pH indicates that aluminium toxicity exists in the subsoil. Aluminium toxicity reduces root growth and function. Consequently, if aluminium toxicity does exist the calculation of plant available water and readily available water need to be revised downward to 76.9 mm and 27.4 mm. This is a relatively small amount of readily available soil moisture such that this soil will require small frequent irrigations preferably informed by a quality soil moisture monitoring system. In relation to irrigation, the refill point for the A1 horizon is between 37 % (50 kPa) to 34 % (100 kPa) soil moisture. Likewise, the low CEC throughout the soil profile indicates this soil has little ability to retain and supply nutrients, such that frequent fertigation with small amount of fertiliser is advisable to prevent loss of nutrients below the root zone. The hardness of the A2 horizon results from its sodicity, attempts to relieve this harness or compaction through deep ripping are only likely to yield short term benefits as this soil will naturally re-compact. The B22 horizon may be sodic in adjacent locations or at greater depth. Further testing is advised before installation of subsoil drains, as sodic soils tend to disperse and block subsoil drains.

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