RISK OF IMAZAPYR LEACHING IN THREE ARGENTINEAN SOILS

Abstract

Imazapyr is a broad-spectrum herbicide that belongs to the imidazolinone chemical family. In Argentina it is used on Imidazolinone-tolerant corn and sunflower Clearfield ®. Due to its low adsorption capacity, and high desorption capacity and soil persistence, imazapyr is prone to leaching into groundwater. There is a lack of information available regarding groundwater leaching of imazapyr in Argentina. Therefore, the objective of this study was to determine the risk of imazapyr leaching in three Argentinean soils (Tandil, Anguil and Cerro Azul sites). The indexes applied to estimate lixiviation risk of the herbicide imazapyr were GUS (Groundwater Ubiquity Score), RF (Retardation Factor) and AFT (Attenuation Factor log-transformed). The indexes were calculated using environmental properties (half-life and adsorption) obtained from batch experiments, and from pesticides databases. AFT was calculated for three rates of net groundwater recharges: 0.3, 1.1 and 2.3 mm day-1. According to the GUS and AFT indexes, imazapyr has a high leaching potential, following the order Tandil > Cerro Azul > Anguil soils. The results indicate that the weak adsorption and high persistence of imazapyr may increase its movement in the soil profile and the risk of groundwater pollution.