In this study, the seasonal variations in concentration levels of selected heavy metals (As, Cd, Cu, Fe, Pb and Zn) in soils within the vicinity of the three major poultry farms in Osun State, South-Western Nigeria were investigated during two major seasons of Nigeria to ascertain the possible environmental impact of these agricultural farmland. Results of the atomic absorption spectrophotometric (AAS) analysis of samples of the soils revealed that for the majority of heavy metals in both seasons, the mean concentrations in the soils are above background levels and permissible limits recommended for typical agricultural soils in some countries as indicated by the following ranges (µgg-1): As, 508.06-956.21; Cd, 1.39-3.36; Cu, 36.95-76.38; Fe, 306.48-720.11; Pb, 64.11 –131.72 and Zn, 92.63-192.23, with a variation pattern in the order: As>Fe>Zn>Pb>Cu>Cd. The order of accumulation of metals in the agricultural poultry farmland locations is: Odunola > Worgor >Agboola. Contamination factors for Zn, Cd, As, Fe, Cu and Pb in the areas under investigation ranged from considerable to very high contamination, while As, Cu, Fe, Pb and Zn had deficient to minimal enrichment while Cd demonstrated severe enrichment. Geo-accumulation index values for the metals in the soils also showed that the environment surrounding the poultry farms is extremely polluted with Cd, and to a lesser degree with As. Iron, Cu, Pb and Zn showed moderate pollution status.

Keywords: Poultry farm soil, Heavy metal contamination, enrichment factors, contamination factor, pollution load index, geo-accumulation index, cluster analysis