Transport of Atrazine Via Leaching in Agricultural Soil with Mineral Oil Addition

Adjuvants, such as mineral oils, are widely used in the application of herbicides by reducing the drift and evaporation of the droplets and by increasing herbicide uptake by the plant. However, little is known about how mineral oil behaves when in contact with the soil. Thus, the objective of this research was to evaluate the transport of atrazine via leaching with the addition of mineral oil in a soil agricultural under laboratory conditions. To quantify the concentration of the herbicide along the profile of the very clay soil column (30 cm), 14C-atrazine (ring-U-14C) was used with 16,667 Bq of radioactivity per column in volume of 200 mL solution and 0 (control), 1, and 2% mineral oil (v/v) was added in the application volume. Atrazine was applied at the highest commercial dose recommended for sugarcane (4 kg ha-1). After simulation of a precipitation of 200 mm for 48 h, each column was sectioned into six parts of 5 cm and the analytes of each soil sample and the leachate were quantified by liquid scintillation spectrometry. The atrazine remained in the superficial layer of the soil, between 0 and 10 cm of depth, independent of the addition of mineral oil. No atrazine residues were detected in the leachate solution (> 30 cm) in any evaluated treatment. The addition of mineral oil at the time of application of pre-emergence atrazine did not interfere with the transport of this herbicide in the soil profile agricultural via leaching; therefore, the adjuvant may have positive effect only in the herbicide-plant relationship. RESUMO: Os adjuvantes, como os óleos minerais, são amplamente utilizados na aplicação de herbicidas por reduzir a deriva e a evaporação das gotas, bem como por aumentar a absorção do herbicida pela planta. Contudo, pouco se sabe como o óleo mineral se comporta quando em contato com o solo. Assim, o objetivo desta pesquisa foi avaliar o transporte de atrazine via lixiviação com adição de óleo mineral em um solo agricultável sob condições de laboratório. Para quantificar a concentração do herbicida ao longo do perfil da coluna de solo de textura muito argilosa (30 cm), foi utilizada a 14C-atrazine (ring-U-14C) com 16.667 Bq de radioatividade por coluna em volume de 200 µL de solução e adicionado 0 (controle), 1% e 2% de óleo mineral (v/v) no volume de calda de aplicação. A atrazine foi aplicada na maior dose comercial recomendada para a cultura de cana-de-açúcar (4 kg ha-1). Após a simulação de uma precipitação de 200 mm durante 48 horas,