Distribution of copper and zinc fractions in red soil as influenced by fertilizer application

A laboratory experiment was carried out to examine the influence of nitrogen (N), phosphorus (P), and potassium (K) application on the various fractions of soluble plus exchangeable (EX), weakly specifically adsorbed (SA), iron-manganese (Fe-Mn) oxides bound (OX), organic matter complexed (OM), and residual (RES) copper (Cu) and zinc (Zn) in a red soil (Typic Udic Ferrisols). Application of urea at rate of 200 mg N kg(-1) significantly decreased the EX fraction, but increased the SA and/or OX fractions of both metals. Supply of 80 mg P kg(-1) caused a decrease in the EX fraction, and a rise in the SA fraction of Cu. However, the EX fraction of Zn was increased, but the OX fraction decreased by P supply. Addition of 100 mg K kg(-1) led to an increase in the EX fraction, while a decrease in the SA and/or OX fractions of the metals. Applying chemical fertilizers had no significant influences on the other fractions of metals. These findings suggest that in heavy metal contaminated soil applying fertilizers does not only provide plant nutrients, but may also act to change the speciations and thus bio-availability of heavy metals.