Soil Acidification and Natural Resource Management: Directions for the Future

Soil acidification is one of Australia's major land degradation problems. About half of the more intensively used agricultural land in Australia is acidic, and the area is expanding. The gross value of agricultural production lost nationally each year due to soil acidity has been estimated at $1585 million, compared to $187 million for dryland salinity. For NSW alone the corresponding estimates are $378 million for soil acidity and $6 million for dryland salinity. The rate of spread of soil acidity is not known with any degree of certainty. One estimate is that, in the absence of remedial action, an additional 2.7 to 6 million hectares of Australian agricultural land could reach the strongly acidic threshold (pHCa = 4.8) each year.Although it has been known for over 60 years that Australian agricultural practices can cause soil acidification, recognition of its significance has been slow. Currently farmers perceive soil acidity to be not much more of a problem than dryland salinity. Soil acidity has been managed mainly as an agronomic, paddock scale problem, and there has been considerable research into liming and plant adaptation to acidic soils. These areas will continue to be important. However the great extent of the problem, limitations to the economic viability of liming on more extensive grazing land, and the occurrence of off-site and long term effects, indicate that additional work is needed to address the problem from a broader natural resource management perspective. The causes of soil acidification have features in common with those of salinity and erosion, in that all are associated with increased leakage of water and nutrients from agricultural systems compared to pre-European landscapes. There has been little integration of research and management of soil acidification with other hydrologically based soil degradation problems.