PERSISTENCE, MOBILITY AND DEGRADATION OF HEXAZINONE IN FOREST SILT LOAM SOILS.

This study reports the persistence, degradation, vertical leaching and lateral movement of hexazinone, 3-cyclohexyl-6-(dimethylamino) -1-methyl-1,3,5-triazine-2,4(1H,3H)-dione, in a white spruce plantation treated at 4. 3 kg active ingredient (ai)/ha by a helicopter equipped with a MICROFOIL boom. Sixty six percent (66%) of hexazinone was degraded and dissipated at the end of 104-day monitoring, decreasing from 7. 12 ug/g (9 days) to 2. 09 ug/g (104 days). The higher amount of metabolite-A (30-50% of hexazinone detected) compared to metabolite-B (0. 12%) indicated higher hydroxylation than demethylation activity in the silt loam soil. Leaching of hexazinone and its metabolites from the surface organic to the underlying 0-15 cm mineral soil layer was found only in the 55-day sample. No residues of hexazinone and its metabolites were detected at deeper (15-30 cm) soil horizons. The lateral movement was not detected at distances of 20 m and 40 m outside of the treated block on a 5-10% slope.