Determination of chemical forms of copper and their relationships with plant responses and soil properties in some soils of Golestan Province

Phytoavailability of copper (Cu) depends on the relative distribution of different chemical forms, which is a function of soil properties. To partition the total Cu into exchangeable (Ex), carbonates-bound (Car), organically bound (OM), Mn-oxide-bound (Mnox), amorphous Fe-oxide-bound (AFeox), crystalline Fe-oxide-bound (CFeox) and residual (Res) forms a sequential extraction procedure was conducted in 10 soils of Golestan province that varied in physical and chemical properties. The results revealed that about 0.3, 0.4, 4.5, 1.3, 26, 30.3 and 37.2% of the total soil Cu was present in mentioned forms, respectively. Soil pH was significantly negatively correlated with Cu associated with Mnox and AFeox at 5 and 1% level, respectively. Organically bound Cu did not show significant correlations with any soil properties. Correlation coefficient between calcium carbonate equivalent and carbonate-bound Cu was not significant. DTPA erxtractable Cu was significantly positively correlated with clay content. The Cu concentration in plant was negatively correlated with Cu concentrations in the exchangeable (Ex), carbonates-bound (Car) and organically bound (OM) forms. A negative correlation was observed between total uptake of Cu in plant and Cu concentration in the exchangeable (Ex) form.