Copper Fractions in Soils of Punjab

To study the distribution of native copper fractions in alluvium-derived soils of Punjab and their relationship with important soil characteristics, fortyfive representative surface (0–0.15 m) soil samples were collected from four major agro-climatic regions of Punjab viz., undulating, central, western and flood-plain regions. Total and DTPA-extractable Cu in these soils ranged from 3 to 26 and 0.1 to 2.6 mg kg⁻¹ soil with average values of 14 and 0.8 mg kg⁻¹ soil. A sequential fractionation shlowed that 0.7 to 5.3 per cent of total soil Cu was exchangeable, 1.5 to 9.8 per cent was weakly adsorbed, 2.0 to 10.7 per cent was moderately adsorbed, 0.3 to 3.7 per cent was strongly adsorbed, 0.4 to 13.3 per cent was associated with organic matter. 0.9 to 8.4 per cent was occluded and bound by carbonates and other acid soluble minerals and most of the total Cu (45 to 93 per cent) was in the residual fraction. All the chemical fractions of Cu were significantly correlated with each other and organic carbon status of soils.