Plant availability of copper in a copper-deficient soil in relation to copper concentration and speciation in the soil solution

Abstract

In order to understand the mechanisms which control the availability of copper to plants, it is essential to have some knowledge of the concentration and form of copper in the soil solution. Determination of the partitioning between complexed and uncomplexed copper ions in the soil solution is of fundamental importance, as uptake by plants is considered to be an active process involving uncomplexed copper ions (Barber, 1984). Several studies have shown that the speciation of copper in the soil solution is highly pHdependent (e.g. Hodgson et al., 1965; Hodgson et al., 1966; Sanders, 1982). At pH values greater than pH 6 a significant proportion of soil solution copper exists as soluble organic complexes while at lower pH values an increasing proportion of total solution copper is present as the uncomplexed cupric ion (Cu2+).