Dissipation and transport of quizalofop-p-ethyl herbicide in sunflower cultivation under field conditions

Abstract

In the present study, the field dissipation and transport of quizalofop-p-ethyl by water and sediment runoff were investigated in sunflower experimental cultivation under Mediterranean conditions. The cultivation was carried out in silty clay soil plots with two different slopes of 1 and 5 %. The soil dissipation rate of quizalofop-p-ethyl was fast and can be described by both single first-order (SFO) and Gustafson and Holden (first-order multi compartment (FOMC)) kinetics. The half-life of quizalofop-p-ethyl ranged from 0.55 to 0.68 days and from 0.45 to 0.71 days when SFO and FOMC kinetics were applied, respectively. No herbicide residues were detected below the 10-cm soil layer. A single detection of quizalofop-p-ethyl was observed in runoff water (3 days after application (DAA)) at relatively low concentrations (from 1.70 to 2.04 μg L⁻¹). In sediment, it was detected in the samplings of 3 and 25 DAA at concentrations that never exceeded 0.126 μg g⁻¹. The estimated total losses of quizalofop-p-ethyl as percentage of the initial applied active ingredient were low both in water and sediment (less than of 0.021 and 0.005 %, respectively). Quizalofop-p-ethyl residues were detectable for 18 DAA in the stems and leaves of the plants and 6 DAA in the root system. No herbicide residues were detected in inflorescences and seeds of sunflower plants. Experimental data showed minimal risk for the contamination of soil and adjacent water bodies.