Effect of wheat (Triticum aestivumL.) rhizosphere on fractionations of copper in some sewage sludge amended soils

Abstract

Our purpose was to quantify the effect of rhizosphere processes on the fractions of Copper (Cu) in 10 soils amended with sewage sludge under greenhouse conditions by using a rhizobox. For amended soils, 1% (w/w) of sewage sludge was added to soil samples and then amended soils were incubated at field capacity, for 1 month. After incubation, soils were put in rhizobox and seeds of wheat were planted. Plants were harvested after 8 weeks and rhizosphere and bulk soils were separated. Fractions of Cu in the rhizosphere and bulk soils were determined. The results showed that Cu extracted using several extractants in rhizospheric soils were significantly (P<0.01) lower than in bulk soils. In the rhizosphere of amended soils the average of residual Cu, Cu associated with iron-manganese oxides, Cu associated with organic matter, Cu associated with carbonates and exchangeable Cu were 18.8, 2.10, 1.00, 0.37 and 0.24 mg kg -1 respectively, whereas above fractions in the bulk soils were 18.1, 2.43, 0.80, 0.42 and 0.30 mg kg -1 respectively. This study illustrated that Cu-fractions in the wheat rhizosphere were different compare to bulk soils in sewage sludge amended soils.