Stream run-off losses and soil and grass residues of triclopyr applied to hillside gorse

Abstract

Abstract Gorse and pasture grass on a hillside area of 0.9 ha was sprayed with 3.57 kg acid equivalent of the butoxyethyl ester of triclopyr. Water from an adjacent stream was sampled continuously for 6 months, and soil and grass samples were collected 7 times over 8 months. Triclopyr residues were detected in three water samples and the largest mass was lost in the first significant rainfall of the study. A total of 103 ± 40 g (2.9 ± 1.1%) of the amount applied, was lost in stream flow. No triclopyr residues were observed in samples taken at the catchment outlet. Soil half-life was about 100 days and was comparable with other values in the literature. The grass concentrations declined exponentially to yield halflives of 30 days for the period 2-249 days after spraying. Concentrations of triclopyr in grass and soil samples taken from sites below large gorse bushes increased over the first 32 days but declined similarly to samples from exposed sites, after the first significant rainfall of the study.