Beneficial effects of amendments were also observed in terms of soil phytotoxicity, as reflected by the root elongation of L. sativa in initially non-vegetated sites for the COW, POULTRY and, especially, PAPER treatments (Fig. 3, Table S2). Interestingly, we found a linear negative correlation (p b 0.01) between L. sativa root elongation and metal CaCl2
-extractability (vegetated sites: r = −0.77 and −0.84 for Pb and Zn, respectively; non-vegetated sites: r = −0.70 and −0.85 for Pb and Zn, respectively), supporting the potential use of the root elongation bioassay for the assessment of soil metal bioavailability in metal stabilization processes under field conditions (Galende et al., 2014).