Determination of Copper Fractions and their Relations with Soil properties in Some Soils of East Azerbaijan Province

Knowledge about different forms of Cu and determining the amount of each one provides useful information for evaluation of soil Cu status and also understanding soil Cu chemistry. To obtain such information, the amount and distribution of Cu in different fractions of 21 composite soil samples of East Azerbaijan Province were determined by modified sequential extraction procedure introduced by Singh et al and the relationships of these fractions with each other and with soil properties were also investigated. According to the results, total Cu concentrations of soils ranged from 21.50 to 90.57 mg/kg with a mean value of 37 mg/kg. Sand and silt percentage with Cu associated with amorphous Fe oxides had significant correlation. Silt content had significant correlation with organically copper and amorphous Fe oxides bounded Cu. Both calcium carbonate equivalent and active calcium carbonate equivalent had significant correlation with exchangeable copper. Among the copper forms, Cu-Ex, Cu-CFeOX and total Cu had positive and significant relations with soluble Cu and among them Cu-CFeOX had highest correlation coefficient value (r =0.53*). The order of various forms of soil Cu was found to be as follows: Residual copper (Cu-Res) > crystalline Fe oxides bound (Cu-CFeOX) > amorphous Fe oxides bound (Cu-AFeox) > organically bound (Cu-OM) > carbonates bound (Cu-Car) > soluble exchangeable (Cu-Ex) > Mn oxide bound (Cu-Mnox). In this study a significant correlation was also observed between some forms of Cu, which is presumably a reflection of the existence of a dynamic relation between them in soil.