| Abstract: | The effects of copper (Cu) application on the Cu distribution in various pools were investigated in laboratory and pot culture experiments with two Alfisols. The total soil Cu was fractionated into water‐soluble plus exchangeable (CA‐Cu), inorganically‐bound (AAC‐Cu), organically‐bound (PYR‐Cu), oxide‐bound (OX‐Cu), and residual (RES‐Cu) forms. The relative contribution of these fractions to Cu uptake by wheat was calculated through path coefficient analysis, a statistical technique that differentiates between correlation and causation. Copper fertilizer was applied at rates of 0, 5, and 10 mg (kg soil)—1 and FYM at rates of 0 and 10 t ha—1. Results indicated that the amounts of Cu present in CA‐Cu were very small. The CA‐Cu, AAC‐Cu, PYR‐Cu, and OX‐Cu fractions were increased and RES‐Cu was not significantly affected by the Cu application. No significant variation (P ≤ 0.01) was observed between Cu application with and without FYM on the distribution of different fractions of soil Cu except PYR‐Cu in Patancheru soil. Among the levels, application of 10 mg Cu (kg soil)—1 showed the maximum increase in different fractions of soil Cu. The per cent increase in Cu concentration in different fractions followed the order CA‐Cu > AAC‐Cu > PYR‐Cu > OX‐Cu > RES‐Cu. The path analysis showed that the PYR‐Cu and AAC‐Cu are the most important fractions for maintaining the available Cu pool in soils. |
