Doses de Cd, Pb, Cu, Zn e Ni em latossolos: efeitos no solo e em plantas de alface e feijão / Doses of Cd, Pb, Cu, Zn and Ni in Oxissols: efects in soil and in plants of lettuce and common beans

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Two experiments were carried out in greenhouse, aiming to study the absorption of cadmium, lead, copper, zinc and nickel and their distribution in plants of lettuce and common beans. The comercial cultivars of alface (Regina de Verão) and common beans (Carnaval) were grown under increasing doses of cadmium (0, 1, 2, 4, 8 and 16 mg/dm3), lead (0, 23, 46, 92, 184 and 368 mg/dm3), copper (0, 8, 16, 32, 64 and 128 mg/dm3), zinc (0, 23, 46, 92, 184 and 368 mg/dm3) and nickel (0, 4, 8, 16, 32 and 64 mg/dm3), in 3 dm3 jars containg Red-yellow Latossolo (Oxissol), in three different textures: clayey (LVATG), medium (LVAJP) and sandy (LVATM). The soil samples were limed with CaCO3+MgCO3 (ratio 4:1), to reach a percentage of base saturation equal to 60%, and fertilized with macro and micronutrients according to the crops requirement. Lettuce was harvested 50 days after the transplanting of the seedlings. For commom beans, two plants were harvested 50 days after sowing (stage R5) and two left to be harvested at the physiological maturation of the grains (stage R9). After the plant sampling, soil samples were colected for analysis. For each experiment, it was used a ramdomly blocks experimental design with three replications. The treatments were distributed based on a baconian design arranged as a factorial [1x3x(26)]x3, with 1 plant species, 3 soils, 26 treatments and 3 replications. The aerial parts of lettuce plants and the roots, stems, leaves and grains of common beans plants were analysed for determination of Cd, Pb, Cu, Zn and Ni concentrations and the metal contents for the plant parts were calculated. The soil samples were also analysed for determination of Cd, Pb, Cu, Zn and Ni concentrations, after extraction with Mehlich-3 (M-3). There was increase of the metals concentrations in the aerial parts of the lettuce plants, as the doses apllied to the soil increased. The metal concentrations in the lettuce dry matter were, in general, above the values considered toxic for the plant. In the fresh matter, the metal concentrations were above the limit allowed for human intake, by the Brazilian legislation. The dry matter yield of the lettuce plants was not affected by the doses of Cd, Pb, Cu and Ni added to the soils (only the added doses of Zn caused decrease). In common beans, the concentrations of Cd, Pb, Cu, Zn and Ni, in all plant parts, increased as a function of the doses added to the soil and were above the limit for metal toxicity for the crop. In the grains, the metal concentrations were above the values allowed by the Brazilian legislation for human intake (exception for Cu). In general, the dry matter yield of commom beans was not affected by the metals added to the soils. There were positive and significant correlations between the contents of Cd, Pb, Cu, Zn and Ni in the commom bean leaves and the concentrations of these metals in the soils, determined after extraction with M-3. This indicates eficiency of the extractor M-3 for evaluation of the availability of these metals for the common bean plants. For lettuce, the correlations between the contents and concentrations of the elements in leaves and their amounts extracted from soil with M-3 were highly significant only for Cd and Ni. For Cu, these correlations, although significant, were below 50 %. The correlation between the contents of Zn in lettuce leaves and its amounts extracted from soil with M-3 was not significant, however, the correlation between the Zn extracted with M-3 and its concentrations in the leaves was higly significant. For Pb, despite of the positive and high significance between the extracted from soil and the concentration and content in the aerial part, the coefficient of determination of the linear regression was below 50%.

ASSUNTO(S)

solos metais pesados mehlich-3 plant nutrition ciencia do solo soil heavy metal mehlich-3 nutrição de plantas

ACESSO AO ARTIGO

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