Soil acidity is a serious soil degradation process, estimated to affect half of all agricultural land in NSW. This is eight to nine times the area affected by dryland salinity. Through its effect on plant growth, soil acidity contributes to rising water tables and associated dryland salinity. The direct agricultural effects of soil acidity are widely recognised and documented. These include a reduction in crop and pasture yield and restrictions on what plant species can be grown. In addition to these on-farm effects, soil acidity has serious downstream consequences for landholders, townships and local government. These downstream, or off-site, effects of soil acidity are difficult to quantify due to the complex interaction of many degradation factors. It is possible to explain their nature but difficult to be precise about their magnitude.