Efficiency of Extractors of Heavy Metals from Urban and Industrial Waste Applied to Soil Cultivated with Soybean.

The aim of the study was to verify the efficiency of DTPA soil testing and a mixture of organic acids (OA MIX ) 1.0M acetic acid , 0.72M citric acid , 0.49M lactic acid , 0.12M oxalic acid  to assess the bioavailability of Cd , Cr , Pb , Ni and Zn from different waste added in Oxisol at UNESP farm, Botucatu, São Paulo state, Brazil. The residues were biodigested sewage sludge, centrifuged sewage sludge, both urban origin; the steel slag, from the steel industry and the lime mud from pulp and paper industry, broadcasted in doses of 0.0, 2.0, 4.0 and 8.0 Mg ha^{- 1} (dry basis) in 2002, being reapplied every two years from 2004 to 2010. The levels of these metals were evaluated at depths from 0.0 to 0.10 m and from 10.0 to 0.20 m. The DTPA showed higher extraction power than OA MIX to Cd, Pb and Zn, while organic acids showed higher extraction power of Ni and Cr than DTPA. There was a significant positive correlation between the concentrations of Cr, Pb, Zn extracted by DTPA and the levels of these elements in the leaves and grains of soybean plants. In the case of OA MIX extractor, just the contents of Ni and Zn extracted correlated with the levels of these elements in the leaves and grains of soybean plants