Pendimethalin and Oxyfluorfen Residues in Pond Water and Sediment from Container Plant Nurseries

Abstract

A two-year herbicide residue study was conducted at a commercial nursery to determine the presence of herbicide residues in pond water and sediment following normal production cycles. The runoff water from irrigation and rainfall was contained on the nursery and reused for irrigation. The nursery site was approximately 60 ha with two interconnected ponds, one for containment of runoff water and one serving as a source of irrigation water. The most commonly used herbicides were oxyfluorfen plus pendimethalin (granular formulation-Ornamental Herbicide 2); approximately twice as much herbicide was applied during the second year of the study. Herbicide levels found in pond water and sediment were approximately two-fold greater during the second year corresponding to the increase in active ingredients applied. The highest concentration of oxyfluorfen found in water and sediment was 0.04 μg/ml and 4.0 μg/g, respectively. The highest concentration of pendimethalin found in water and sediment was 0.008 μg/ml and 14.3 μg/g, respectively. In irrigation water samples, the highest concentration of oxyfluorfen and pendimethalin detected was 0.005 μg/ml and 0.002 μg/ml, respectively. The herbicides did not accumulate in water or sediment over the two-year period. No landscape plant phytotoxicity problems are likely at the herbicide levels detected in irrigation water samples.