Atributos químicos do solo e produção de abacaxizeiro adubado com lodo de esgoto

Abstract

The process of urban sewage treatment in Sewage Treatment Plants generates a residue called sewage sludge that is rich in organic material and essential elements to plants and whose disposal in the environment should be a concern when planning Sewage Treatment Plants. Among the uses most applied for final disposal of this residue, directing it for agricultural purposes is the best way to equate the problem, since the flow of matter between the countryside and the cities becomes a two-way road. In view of that, the objective of this study was to evaluate the production and the nutritional status of five cultivars of irrigated pineapple, as well as the chemical properties of dystrophic and environmental aspects such as heavy metal accumulation and microbiological contamination of fruits after sewage sludge and mineral fertilizations. The study was conducted in the experimental area located in the municipality of Janaúba-MG. The treatments were arranged in a factorial 2 x 5 and the experimental design was a randomized block, consisting of two different fertilizers - sewage sludge and mineral fertilizers and five pineapple cultivars (Pérola, Vitória, Smooth Cayenne, MD-2, and IAC Fantástico), with four replications. N was adopted as a reference for the calculation of the sewage sludge dose needed to meet the pineapple culture demands, being supplemented with mineral sources of P and K. The sewage sludge fertilization promoted pH decrease and increase in levels of organic matter, phosphorus, calcium, iron and zinc in soil, especially in the layers up to 0.40 m of soil depth. The leaf area index, regardless of the type of fertilizer, was higher in cultivar Smooth Cayenne, followed by 'IAC Fantástico', 'Vitória', 'Pérola' and 'MD-2', in that order. The sewage sludge fertilization showed lower leaf content of N and higher leaf content of Fe and Zn compared to mineral fertilization. The sewage sludge fertilization provided statistically equal yields compared to mineral fertilization for all crops. Cultivar Smooth Cayenne had the highest fruit weight and average productivity of 125 t ha", followed by 'MD-2' and 'IAC Fantástico', with 98 and 90 t ha¹, respectively. Pérola and Vitória had lower productivities and accounted for 84 and 81 t ha- 1, respectively. The sewage sludge fertilization increased the soil content of Cu and Zn and the leaf content of Zn. The fruit contents of As, Pb, Ba, Cu and Zn were not affected by the type of fertilization and the contents of Cr, Ni and Cd were not detected by the method used. No contamination by total and thermotolerant coliforms was detected in the fruits of Pérola, IAC Fantástico, MD-2 and Smooth Cayenne. However, there was contamination by total coliforms in fruit skin and flesh for both types of fertilization, however it was below the limits established by Brazilian law. Sewage sludge might be used in the fertilization of irrigated pineapple cultivars.