COPPER BIOAVAILABILITY IN CALCAREOUS SOIL SAMPLES .2. RELATION TO THE CHEMICAL FRACTIONATION OF COPPER

The bioavailability of copper is usually measured by chemical reagents such as EDTA. However, evidence of cupric deficiency for plants may be observed without the chemical test for it. Thus, the aim of this study was to apply classical sequential extraction procedures, used in environmental studies, in order to obtain a chemical fractionation of copper and to examine the possible relations between these fractions and the bioavailability of copper. The study was performed on calcareous soil samples collected in Eastern France and corresponding to an agronomical assay to study copper deficiency. The results of the copper fractionation were described in a first paper. In this paper, the possible relations between copper fractionation and grain yields obtained in the plots of the agronomical assay will be discussed. From a statistical point of view, there was no significant correlation between the copper fractions and yields, but significant relations between sampling year or sampling location and yields are observed. As a conclusion, a chemical fractionation of copper does not seem appropriate in order to predict its bioavailability.