Ametryn Leaching in Soils from the Sugarcane Region in Northeastern Brazilian

ABSTRACT Ametryn is one of the most widely used herbicides in the sugarcane culture. Little is known about the interactions between this herbicide and the attributes of soils in the sugarcane region of northeastern Brazil. This knowledge, before recommending herbicide, will minimize the negative effects on the environment, particularly on water resources, and will ensure weed control efficacy. In this work, ametryn leaching potential was estimated through bioassays and chromatography, in five soils from the sugarcane region in northeastern Brazil: Quartzarenic Neosol (Entisol); Red Argisol (Ultisol); Ferrihumiluvic Spodosol (Spodosols); Red-Yellow Acrisol (Oxisol) and Haplic Cambisol (Inceptisols). To achieve this, columns were prepared with samples of the respective soils. On top of these columns ametryn was applied and, 12 hours later, a 60 mm rainfall was simulated. After water draining (72 hours after herbicide application), the columns were longitudinally opened to withdraw samples of each soil, every 5 cm. On some of these samples, ametryn quantification was performed by high-performance liquid chromatography and, on the others, biological assays were performed to confirm the results. Ametryn mobility was influenced by the physical-chemical characteristics of soils, mainly by organic matter content, texture and cation exchange capacity (CEC). However, this cannot be considered for Ferrihumiluvic Spodosol, whose cementing characteristics restrict the infiltration of water and organic compounds. Increased leaching ametryn occurred in Quartzarenic Neosol (Entisol), with higher herbicide concentration in the 5 to 10 cm depth layer, in relation to the 0 to 5 cm surface layer, indicating possible agronomic efficiency loss and higher risk of groundwater contamination