Sorption, dissipation, and leaching of metsulfuron in Colorado soils

Metsulfuron sorption, dissipation, and leaching were studied in six Colorado soils. Sorption was studied in the laboratory by batch equilibration of soil horizons from the surface to 1 m deep found in each study area. Kd was correlated to several soil parameters with pH (-0.773) and percent organic matter (OM) (0.666) the strongest, although low. Kd generally decreased with depth at each site and ranged from 0.10 to 0.83 among surface soils. The lowest Kd was in the soil with the highest pH. Leaching and dissipation were studied by high-performance liquid chromatography/ultraviolet analysis of field samples collected 1 m deep. Bromide ion as conservative tracer was applied concurrently with metsulfuron at the four dryland and two irrigated sites. In most cases, metsulfuron was found only in upper horizons, and the half-life ranged from 11.8 to 27.7 d, the shortest being in the soil with highest percent OM and lowest pH. Very little leaching below the surface horizon was detected in any soil.