Abstract

O. O. Awotoye, D. J. Oyedele and B. C. Anwadike

Field trial was conducted with the view to determining the ideal rock phosphate (RP) and the level of cow dung fertilizer combination with respect to heavy metal contamination of soil and crops. Soils amended with Ogun rock phosphate (ORP) were subjected to 1-4 tha-1 of cow dung on which maize (Zea mays (L) _ and okra (Abelmuscus esculentum) were planted. The amended soils were found to be enriched with heavy metals (Pb, Zn, Cu and Cd) more than the unamended soil but were still within the tolerable level with the exception of Cd which had a high value of 5.30 ï?µg g -1 above the critical value of 3ï?µg g -1 . The application of RP in combination with various levels of cow dung elevated the Pb, Zn and Cu content in the tissue of maize relative to the control. The Zn and Pb content of okra were not affected except for Cu and As in soil amended with RP and various levels of cow dung relative to the control. Transfer factor (TF) was higher in the treatment with RP supplemented with 2 t ha-1 of cow dung particularly for Pb and Zn for both crops relative to other treatments. Except for Cu and Zn, increasing the level of cow dung while RP did not increase the TF value of the heavy metals to the crops.