Cu(II) can form stable
complexes with soil organic matter and this fraction of
the adsorbed Cu(II) can not be desorbed by KCl (Guo et
al., 2006). The amount of Cu(II) that complex with soil
organic matter increases with the increase in the content of
the organic matter of the paddy soils, which may account
for the decline of the desorption percentage for previously
adsorbed Cu(II).