Soil Organic Matter Determines Indaziflam Efficiency and Environmental Risk

Abstract

Herbicides can contaminate soil and water, making it essential to understand their sorption and desorption processes. This study evaluated the influence of the physicochemical attributes of 12 tropical soils on indaziflam retention. The batch equilibrium method was used to determine sorption (Kfs) and desorption (Kfd) coefficients, with subsequent fitting to Freundlich isotherms. Soil samples were collected from a depth of 0 to 20 cm, considering pH, organic matter (OM), and cation exchange capacity (CEC) as the main influencing factors. Results showed that Kfs ranged from 1.56 to 24.84 mg (1-1/n) L1/n kg⁻¹, with the highest value recorded in Fluventic Neosol (EF), characterized by high OM content (3.8%) and elevated CEC (13.7 cmolc dm⁻³). Conversely, Oxisol 1 (OX1), which had the lowest OM (1.0%) and CEC (3.99 cmolc dm⁻³), exhibited the lowest Kfs. Desorption was lower than sorption in all soils (Kfd ranging from 6.60 to 74.16 mg (1-1/n) L1/n kg⁻¹), following a similar trend. A significant correlation between OM and both sorption and desorption coefficients was observed only in soils with pH ≥ 5.5. It was concluded that organic matter was the primary factor influencing indaziflam retention. Therefore, its application should consider OM content to optimize weed control efficacy and minimize environmental risks.

Keywords: Organic matter, retention process, bioavailability in the soil, Pesticides