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

The ability of grassed waterways to remediate herbicide loads in runoff wat er was evaluated using simulated and on-site nursery research. Isoxaben plu s oryzalin and isoxaben plus trifluralin were applied to model grassed (zoy siagrass or 'Tifway 10' hybrid bermudagrass) and nongrassed, metal and clay loam waterways, and runoff samples were collected. Grassed waterways reduc ed runoff volume an average of 47% and herbicide residues an average of 56% compared to nongrassed waterways. The smallest herbicide residues were fro m the clay/grass waterways. In a nursery study, isoxaben and trifluralin we re applied to containerized landscape plant production beds. Overhead irrig ation 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 reco vered from the clay/gravel waterway was 32% of applied, and total triflural in recovered was 0.9% of applied. The grass waterway reduced residues of is oxaben and trifluralin by 22 and 66%, respectively, compared to the clay/gr avel waterway.