Corn Response to Added Zn, Cu, Cd, Pb and Ni In Soils.

Three Brazilian Red-Yellow Latossols (RYL) (clay RYLTG from Vicosa, sandy loam RYLTM from Três Marias, sandy clay RYLJP from João Pinheiro), were sampled from the 0-20 cm layer. The soils, in 5 dm³ plastic pots, were limed and incubated for 30 days. Doses of Cd, Pb, Zn, Cu and Ni (nitrates) were added, soils were incubated (25 days, moisture at field capacity) and received 150 mg/dm³ P, 55 mg/dm³ N (NH₄H₂PO₄), 150 mg/dm³ K (KCl); 1 mg/dm³ B(H₃BO₃), 0.14 mg/dm³ Mo [(NH₄)₆Mo₇O₂₄] and 2.5 mg/dm³ Fe [Fe(NH₄)₂(SO₄)₂]. Metals were added (levels 0, 0.5, 1, 2, 4 and 8) combined in a Baconian Matrix (26 treatments, level 1 being 2 mg/dm³ for Cd, 46 for Pb, 16 for Cu, 46 for Zn and 8 for Ni). Two corn seedlings were cultivated in each pot. Plants were harvested 45 days after transplanting, oven dried at 75 ^o C for 72 hours. Dry matter weight was recorded, the samples digested by nitric perchloric digestion and the extracts analyzed for Cd, Pb, Cu, Zn e Ni by ICP emission espectrophotometry. The soil with higher clay and organic matter contents transferred lower metal amounts to the corn plants. Similar effect was observed for the soil with higher Fe oxides contents. Lower metal adsorption in the soils with smaller clay and organic matter contents allowed the plants to accumulate higher metal concentrations in their tissues. Plants grown in the RYLTG (5.40 dag/kg organic matter and 73 dag/kg clay) presented lower concentrations and contents of Cd, Pb, Cu, Zn e Ni in roots and shoots, reflecting the higher metal adsorption in that soil. In the RYLTM (1.80 dag/kg organic matter and 24 dag/kg clay) the metal concentrations in the plants reached higher levels with more severe effect in the dry matter yield in some treatments.