Uso de resíduos de galvanoplastia como fonte alternativa de Zinco para a produção de matéria seca de girassol (Helianthus annuus L.) e de milho (Zea mays L.) em latossolo vermelho (Rhodic Kandiudox)

Abstract

The increase of the global population and industrialization brings, as a consequence, the increase of wastes production. A viable alternative is the use of these wastes in agriculture. Galvanoplasty industries produce inorganic wastes with high contents of heavy metals. One of the ways to the treatment of the acid effluents of a zinc galvanoplasty industry is the neutralization using lime, quicklime, or sodium hydroxide. The residual waste can them be used as soil liming and as a source of nutrients for economic crops interest. For this correct use, it is necessary to evaluate the nutrient quantity that will be available to the plant. The objectives of this study were to assess the effects of three zinc sources (simonkolleite, zincite and zinc sulphate) applied to loamy texture Red Latosol in the ornamental sunflower and corn crops production, and the soil zinc content by different chemical extractors. To achieve these objectives 3 experiments were set up. In the first one, it was applied to the soil, different doses of the original and washed simonkolleite, and it was cultivated ornamental sunflower in pots until flowering. Subsequently, it was evaluated the dry matter production and zinc content in shoot and roots. In the second experiment it was collected soil of the previous experiment, after the sunflower cultivation, and determined the soil zinc content by different chemical extractors, using a multiple vacuum extractor. In the third experiment, it was applied to the soil different doses of zincite and zinc sulphate, and cultivated corn crop in pots for 55 days. After, it was evaluated the shoots and roots dry matter production, the Cu, Zn, Fe, Mn, Ca and Mg shoots content, the Zn Cu, Fe e Mn roots content and zinc soil content determined by two chemical extractors. Through the results obtained, it was concluded that the simonkolleite can be applied in the soil as zinc source for the sunflower crop. The soil and plant zinc content were greater when washed simonkolleite was applied. The mechanical vacuum extraction method was efficient to the evalution of soil zinc content using Mehlich-1 and CaCl2 0,01 mol L-1. The application of different zincites and zinc sulphate in the soil increased corn crop production. However, the corn zinc content was higher when zinc sulphate was used, due to the greater solubility in relation to the zincites. The CaCl2 0,01 mol L-1 soil extractor was effective and presented high correlation between the soil zinc content with the corn zinc content for both zinc sources. The Mehlich-1 extractor wasn?t efficient. Considering the three zinc sources: simonkolleite, zincite and zinc sulphate in equivalent zinc doses applied to the soil, the zinc plant content was greater in the following order: zinc sulphate> simonkolleite> zincite. This order is directly related to the solubility of three sources.