Metals are unavailable to plants when fixed within relatively inert mineral matrices in soil. The success of phytoremediation may be limited by restricted bioavailability of metals in such nonlabile forms. We conducted a pot trial with EDTA added at rates of 0, 0.1, 1.0, 5.0, and 10 mmol kg-1, to soil historically contaminated with sewage sludge to increase the availability of metals to a test crop, Indian Mustard (Brassica juncea). The soil was found to have large total concentrations (mg kg-1) of Cd (59.3), Cu (664), Pb (605), Ni (489), and Zn (1780); the EDTA-extractable metal contents (mg kg-1) were Cd (36.2), Cu (483), Pb (302), Ni (372), and Zn (1280). Isotopic dilution of 109Cd was used to measure labile Cd both (i) chemically (the E value: 28.3 mg Cd kg-1) and (ii) biologically (the L value). Comparison of E and L values was then used to determine whether nonlabile Cd was mobilized by the chelate treatment. Addition of EDTA increased plant uptake of Cd, Zn, Pb, Ni, and Cu from sludge-amended soil...