SORPTION, DESORPTION, HALF-LIFE AND LEACHING OF SULFOMETURON-METHYL IN DIFFERENT SOIL CLASSES1

Abstract

Understanding the behaviour of herbicides in the soil can contribute to adapting the correct dose for efficient weed control with less environmental impact. In this study, we sought to evaluate the factors involved in the sorption, desorption, half-life and leaching processes of sulfometuron-methyl in three soil classes: Cambissolo Háplico (CX) (Inceptisol), Latossolo Vermelho (LV) (Oxisol) and Neossolo Quartzarênico (RQ) (Entisol). The sorption and desorption tests were performed using the “batch equilibrium" method. The studies of degradation and formation of metabolites were estimated from the half-life at the end of 180 days. Leaching potential was estimated by testing PVC columns filled with soil. Analyses were performed by ultra-performance liquid chromatography coupled to a mass spectrometer for herbicide quantification. The higher sorption of sulfometuron-methyl in LV (2.81) is related to the low pH (4.7) and mineralogical composition, mainly due to the higher concentration of Fe and Al oxides in this soil, influencing the lower desorption of the herbicide in LV (0.59). This result contributed to more remarkable herbicide persistence in this soil, reducing the molecules available in the solution for degradation. These results contributed to the longer half-life (19 days) in LV compared to the other soils. Among the studied soils, RQ had the highest risk of transport of sulfometuron-methyl based on the GUS Index (2.2) due to its greater desorption (0.34). The results showed that the studied processes are dependent on the physical, chemical and mineralogical attributes of the different classes of soils.