Two forms of biosolids, with and without lime, were applied to acid soils at 2 sites growing wheat and triticale in central New South Wales. The forms of biosolids used were dewatered sewage sludge cake, and N-Viro Soil which is a lime-amended sewage sludge. Dewatered sewage sludge cake was applied at rates of 0, 6, 12 and 24 dry Mg/ha, and N-Viro soil at 0, 1.5, 3.0 and 4.5 dry Mg/ha. The soil was sampled and analysed at 2 points in time to determine the effect of the biosolids on heavy metal concentrations. Vegetative plant material and grain were also analysed for heavy metal and organo-chlorine pesticide levels.

Zinc and copper concentrations increased significantly with the addition of biosolids, especially with the highest rates of dewatered sewage sludge cake. However, all soil heavy metals were below the maximum allowable soil contaminant concentrations set by Environment Protection Authority, NSW. Cereal species, the addition of lime, and biosolids each affected heavy metal concentrations in plant material, but the responses differed between sites. Also, the changes in heavy metal concentrations in plant material were smaller and less consistent than the changes in soil heavy metal concentrations. The maximum heavy metal concentrations in grain were all below the maximum permitted concentrations of Food Standards Australia New Zealand. There were no detectable changes in the levels of organo-chlorine pesticides in the grain.