BIOSOLIDS IN LEACHING OF HERBICIDES MIMICKING AUXIN IN TROPICAL SOILS

Abstract

Biosolids are residues from the treatment of urban fluids used as a source of nutrients for agricultural and forestry crops. The organic matter contained in this residue and its chemical characteristics may interfere with the behavior of herbicides in the soil. The objective of this study was to evaluate the influence of biosolids on the potential for leaching herbicides mimicking auxin. Two simultaneous experiments were performed: a leaching test of picloram + 2.4-D in soil column with addition of thermally treated biosolids or solarized biosolids and another one to evaluate the effect of leachate application from the leaching tests under inert material. Each type of biosolid was incorporated in sandy soil in the proportions of 0%, 50%, 100% and 150% of the maximum recommended dose for subsurface fertilization for eucalyptus. The soil was conditioned in PVC columns and the herbicide columns based on picloram + 2.4-D ( Turuna (R) Commercial Formulation), corresponding to 240 g L-1 of 2.4-D + 64 g L-1 of picloram at a dose of 3.5 L ha(-1) of the commercial product. The columns were submitted to rain simulation and the resulting leachate was collected, followed by its application in sand-filled pots. The Cucumis sativus was sown along the profile of the soil columns and in the pots. The incorporation of the biosolid, independently of the type and dose tested did not interfere in the leaching potential of picloram + 2.4-D. Symptoms of intoxication were observed along all soil columns and pots. Therefore this residue is not very effective for the resolution of environmental problems caused by the leaching of auxin-mimicking herbicides in the soil.