EFFECT OF SILICON AND PHOSPHORUS ON THE AVAILABILITY OF SOIL HEAVY METALS BY MEHLICH-1 EXTRACTOR

This work was developed on a soil contaminated by heavy metals from a zinc-extracting and industrializing area belonging to the Companhia Mineira de Metais at Tres Marias, Minas Gerais state, Brazil, with a view to evaluating the efficiency of silicon and phosphorus as ameliorating agents of heavy metal toxicity. The samples collected were prepared and incubated into polyethylene flasks, moisture equivalent to 60% of the total volume of pores. 25 treatments were utilized: five doses of silicon (0; 2.340; 6.040; 9.860 and 13.660 mg dm(-3)) and five of phosphorus (0; 90; 180; 360 and 720 mg dm(-3)) with four replicates amounting to 100 experimental units. At 30 and 60 days, samples from each treatment were collected, submitted to water pH analysis and simple extraction by Mehlich-1. The extracted contents received greater influence from both silicon and phosphorous and at a lesser extent from pH. Zn and Cd contents, although reduced, remained above the allowed levels. Pb decreased, influenced by the increase of silicon and phosphorus to level inferior to those permitted.