The contribuition of phosphate fertilizers to the pool of heavy metals in the soil and their transfer to plants and animals is a subject of concern specially among envirommentalists. The objective of this study was to assess the accumulation of heavy metals contained in phosphate fertilizers in the rice plant using a simple sequential method of extraction which could provide information about the availability of heavy metals in the soil. Greenhouse and laboratory experiments used a Xantic Ferralsol previously cultivated with Centrosema pubescens and Brachiaria decubens. The forages received triple superphosphate, termophosphate and North Caroline and Arad rock phosphates at the rates of 50, 100 and 200 mg dm-3 P. There was no increase in heavy metals (Cu, Mn, Cd, Ni, Zn) in the soil or in plants due to the rates of phosphate fertilizers applied. As expected, 6 mol L-1 HCl extracted higher amounts of heavy metals than Mehlich 1 and water extractant.
extractants; phosphorus; fertilizers