An evaluation of the potential of two organic residues as source of micro-nutrients in three soils of Paraná state was studied. Treatments consisted of one dose (38 t.ha-1) of sewage sludge and residue of purified used motor oil both neutralized with CaO+MgO mixture in 3:1 rate. Maize (Zea mays L.) was used as reference plant. After 30 days of seeding, the aerial parts of the plants were cut. They were dried at 70ºC till constant weight and ground. Analysis was undertaken after nitric-perchloric digestion. Micro-nutrients levels in the soils and in the aerial parts of the plants were determined by atomic absorption spectrometry. The results showed a production of the aerial parts of the plants treated with sewage sludge higher than those in other treatments. The micro-nutrients in Terra Roxa - TR were higher than those of Latossolo Vervelho Escuro - LE (Deep Red Latisol) and Podzólico Vermelho - PV (Red Podzolic) soils, respectively. In the aerial part of the maize plants in treated soils concentrations of micro-nutrients Cu, Fe, Mn and Zn were higher than those without treatment.
Sewage sludge; oil residue; environmental pollution; micro-nutrients
