Trace Metals Levels in Inorganic Fertilizers Commercially Available in Nigeria

Aims: To investigate the concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), vanadium (V) and zinc (Zn) in commercially available inorganic fertilizers (calcium superphosphate and urea).
Place and Duration of Study: Urea and superphosphate fertilizers were purchased from a local market in Uyo, Southern Nigeria.
Methodology: A total of twenty seven fertilizer samples were randomly taken representing triplicate samples from three urea and six superphosphate original fertilizer bags. Each sample were digested and extracted using the ethylenediamine tetraacetic acid (EDTA) extraction technique. The elemental analysis was performed using an inductively coupled plasma atomic emission spectrophotometer (ICP-AES) (Optima 3000 – Perkin Elmer).
Results: The analyses indicated the presence of trace metals in commercially available fertilizers sold in Nigeria. Cadmium was found in comparatively high concentrations. Zinc was found present in relatively high concentrations in both urea and phosphate fertilizer samples but As was found in low concentration. By comparison, the superphosphate fertilizer contained higher concentrations of Cu, V and Zn as impurities while urea fertilizer recorded slightly elevated concentrations of Ni, Pb and Cd. The levels of some trace metals in the urea and superphosphate fertilizers analyzed were within the allowable limits.
Conclusion: This study led to the conclusion that urea and superphosphate fertilizers sold in Nigeria could act as sources of trace metal enrichment of agricultural farmlands. Enhanced trace metals in inorganic fertilizers could constitute a threat to human health and the sustainability of farming practices. This study provided a new data for the agriculture and health authorities in Nigeria. Relevant government agency (ies) should regularly monitor trace metals impurity levels in imported fertilizers.