Remediation of herbicides in runoff water from container plant nurseries utilizing grassed waterways

The ability of grassed waterways to remediate herbicide loads in runoff water was evaluated using simulated and on-site nursery research. Isoxaben plus oryzalin and isoxaben plus trifluralin were applied to model grassed (zoysiagrass or 'Tifway 10' hybrid bermudagrass) and nongrassed, metal and clay loam waterways, and runoff samples were collected. Grassed waterways reduced runoff volume an average of 47% and herbicide residues an average of 56% compared to nongrassed waterways. The smallest herbicide residues were from the clay/grass waterways. In a nursery study, isoxaben and trifluralin were applied to containerized landscape plant production beds. Overhead irrigation was applied and runoff water was channeled into either a clay/gravel waterway or a hybrid bermudagrass waterway. Samples were collected for 22 d following application. Isoxaben persisted through 15 d after application. Trifluralin was detected through 2 d after application. Total isoxaben recovered from the clay/gravel waterway was 32% of applied, and total trifluralin recovered was 0.9% of applied. The grass waterway reduced residues of isoxaben and trifluralin by 22 and 66%, respectively, compared to the clay/gravel waterway.