The use of sewage sludge as an organic fertilizer under South African conditions is a popular disposal route. However, the lack of research performed under South African conditions and the conservative nature of the heavy metal guidelines when interpreted as total metal content is limiting the agricultural use of sludge. As part of a greater project, a glasshouse experiment was performed to characterize soil-plant interactions of the main sludge-borne heavy metals (Pb, Cd, Zn and Cu) in 2

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... s (low metal and high metal) to different soil types (clay, loam and sand) on maize seedlings. Yield differences, heavy metal accumulation in plant parts and soil-metal concentrations (Total and potentially available) were determined. The low metal sludge treatment showed the highest yield for maize seedlings when compared to controls [negative control (soil unamended) and positive control (inorganic fertilizer added)]. The amendment of sludge to the soil did indicate higher heavy metal content, although not as predicted due to the difficulty of obtaining a representative sample in the soil.. Except for cadmium, heavy metal values in the soils (at the beginning and end of experiment) exceeded guidelines due to very high background values in the soil. Highest accumulation of heavy metals in plant material occurred in the loam soil treatments due to the metals being more available for plant uptake. No negative effects of heavy metal contamination in plant parts of the crops could be proven. Results showed that the amendment of sludge to different soils can be beneficial to increase crop yields, although soil, plant and water quality monitoring, together with the prevention of metals entering the plant through a management programme, should be required to prevent potential health hazards of sludge application on agricultural land.