Soil chemical attributes
The dominant soil of a land resource inventory area is mapped according to the following key soil chemical attributes: minimum pH, maximum salinity, cation exchange capacity, total carbon, phosphate retention.
Minimum pH classes and their corresponding values are described in relation to plant growth at 0.2–0.6 m depth. pH is an important soil attribute that significantly influences nutrient availability and aluminium toxicity. The pH classes originate from Parfitt (1984), and are as defined in Webb and Wilson (1995).
Maximum salinity in the 0.0–0.6 m zone as percent soluble salts (g/100 g soil). Salinity negatively impacts plant growth, water quality and infrastructure. Salinity classes are as defined in Webb and Wilson (1995) and Milne et al. (1995).
Cation Exchange Capacity
Average Cation Exchange Capacity (CEC) at 0–0.6 m as centimoles of charge per kg (cmoles (+)/kg). CEC is an indicator of the capacity of a soil to hold nutrients and is an important component in effluent absorption and buffering capacity. CEC classes are as defined in Webb and Wilson (1995) and Blakemore et al. (1987).
Total Carbon (%) as a weighted average for 0–0.2 m depth. Carbon content and, more specifically, organic matter are important drivers of soil characteristics such as nutrient attenuation, and soil aggregate stability, and may be reasonable indicators of soil health. The classes are defined in Webb and Wilson (1995) and Blakemore et al. (1987).
Phosphate retention or anion storage capacity (%) as a weighted average for 0–0.2 m depth. Phosphate retention influences phosphate fertiliser requirements and soil structural stability. The classes are as defined in Blakemore et al. (1987) and Webb and Wilson (1995).