The Mount Lofty Ranges lie northeast of Adelaide, South Australia. Soils in the region are being degraded through soil acidification and alkalisation, and the development of both potential and actual acid sulfate soils. These processes affect agricultural production and water quality. Soil testing and survey work in the area have shown significant acidification of acid sulfate and salt-affected soils in subcatchments. The spatial extent of these degraded soils has not been examined previously.

We have developed a method to determine the spatial distribution of soils with differing acidity and alkalinity (pH profiles) over an 80 km² region. The method involves using data from point, toposequence and subcatchment scales to develop simple mechanistic models and a geographic information system. We predicted soil profile pH classes for the 80 km² region and used these to plan the management of degraded soils. The data were also used as a soil degradation indicator for assessment of landscape quality at catchment and regional scale.