Cadmium and the other elements in the soil extractions and
plant digests were measured by inductively coupled plasma optical
emission spectroscopy (ICP-OES Jobin-Yvon, Ultima-C). Metals
from soil solution samples were also measured by ICP-MS (Perkin-
Elmer Elan 6000, LMTG Toulouse. Si concentrations in soil solutions
were measured by the molybdate blue colorimetric method [81]
with a spectrophotometer (Jasco V650).