The objective of this study was to evaluate oxadiazon sorption in different soils of the Brazilian Cerrado, highlighting the correlations of lethal doses of this herbicide capable of inhibiting 50% of the dry matter accumulation of the bio-indicator (LD50) among the chemical characteristics of the soil and its direct and indirect effects. The experiment was carried out in a greenhouse in a randomized block design and four repetitions. Each experimental unit consisted of a pot with increasing rates of oxadiazon and oat (Avena sativa), as the bio-indicator species. For sorption evaluation, washed sand and 22 soils (substrates) from Cerrado Brazilian's Alliaceae cultivated areas were used. LD50 and sorption ratio (SR) = [(LD50soil - LD50sand)/LD50sand] to the substrates were determined. Pearson correlation analysis was performed between the chemical characteristics of the substrates and the LD50 of oxadiazon. A path analysis was quantified, to deploy only the significant correlations estimated in direct and indirect effects of the characters on LD50, which is a basic variable. A more pronounced LD50 (528.09 g ha-1) for the Cerrado soil sample resulted in higher SR (> 53.00), while in the washed sand substrate, LD50 corresponded only to 9.74 g ha-1 of the oxadiazon (available in soil). It was concluded that oxadiazon sorption is influenced by the chemical characteristics of the soils, highlighting the correlation with pH (CaCl2), magnesium content, aluminum, organic matter, organic carbon, and aluminum saturation.
bioassay; neutral herbicide; organic matter
