Sorption of hexazinone, sulfometuron methyl, and tebuthiuron on acid, low base saturated sands

The objective of this research was to determine the sorption of hexazinone, sulfometuron methyl, and tebuthiuron on six acid, low base saturated sands as a function of depth. Sorption Kd values for tebuthiuron on these soils ranged from 0.002 to 3.6 L kg−1 with greatest sorption on soils from the surface 0–5 cm depth and least on soils from depths > 65 cm. Sorption is correlated to OC content of the soil; mean Koc = 39 ± 22 L kg−1. Hexazinone Kd values ranged from 0.0011 to 1.10 L kg−1. Sorption is correlated to soil OC; mean Koc = 19 ± 13 L kg−1. Kd for sulfometuron methyl sorption to soils of 0–20 cm depths ranged from 0.04 to 0.6. Sorption of sulfometuron methyl on soil from depths 65–95 cm was less than in the surface soils and was approximately equal to that of tebuthiuron at the same depth. In contrast to tebuthiuron and hexazinone, using data for all soils and from all depths, sorption did not correlate to OC content. It appears that factors affecting sorption change with soil depth. For instance, sorption is correlated to OC for surface soils (0–20 cm depths), Koc = 5.4 ± 3.4, and for subsurface soils (65–95 cm depths), Koc = 44 ± 22. It appears that once these three herbicides leach past the top 10 cm of these soils, retardation of the herbicides would be slight.