Absorption and toxicity of copper and zinc in bean plants cultivated in soil treated with chicken manure

The interaction between copper, zinc, and chicken manure, when added to soil, was studied in a greenhouse setting. Copper sulfate and of zinc chloride at concentrations of 0.5 to 2.0 mmol kg(-1) were added separately to pots containing 3.0 kg of dystrophic dark red latosoil (LEd) plus 1,0% (m/m) pH 4.2 chicken manure. IAPAR 57 beans were used as test plant and cultivated in the experimental soils for 30 days. Plant growth in terms of dry weight and the concentrations of copper and zinc in the aerial part of the plants were determined. Bean plantings were repeated four times, at four-month intervals. A 20% decrease in dry weight was observed when amounts of copper or zinc equal to or geater than 1.0 or 2.0 mmol kg(-1), respectively, were applied to the soil over an average of four plantings. For these concentrations, the average amount of metal found in the plant was 13.4 mg kg(-1) for copper and 224.8 mg kg(-1) for zinc. Chlorosis of the leaves in the bean plants was also observed. The copper and zinc concentrations in the treated soil were determined using different extractants. Among the solutions evaluated for the extraction of available zinc, 1.0 M ammonium acetate, pH 4.8, showed a better correlation with the metal concentration in the plant. As for copper, the best correlation was found with the Mehlich-1 extractant.