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United States Department of Agriculture

Agricultural Research Service

Title: Sorption of Hexazinone, Sulfometuron Methyl, and Tebuthiuron on Acid, Low Base Saturated Sands.

Authors
item Koskinen, William
item Stone, D - USDA-FOREST SERVICE
item Harris, A - USDA-FOREST SERVICE

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 12, 1996
Publication Date: N/A

Interpretive Summary: Hexazinone, sulfometuron methyl, and tebuthiuron are herbicides used for forest production purposes in the Lake States region. Very little research has been done on these herbicides in soils of the Lake States region, which has large areas of sand soils that have a potential for extensive leaching of herbicides, particularly if the herbicide is slightly sorbed and does not readily degrade. The objective of this research was to determine the adsorption of hexazinone, sulfometuron methyl, and tebuthiuron to six sands from northeast Minnesota, northern Wisconsin, and Upper Michigan and to correlate adsorption to soil properties. Adsorption of hexazinone was substantially less than that of tebuthiuron on samples from different soils and depths. Soil organic matter is the principal adsorbent for tebuthiuron, particularly when clay content is low, as in these soils. Adsorption of sulfometuron methyl to surface soils was significantly lower than that of either hexazinone or tebuthiuron. Sorption of sulfometuron methyl on subsurface soils 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, sulfometuron adsorption did not correlate to organic carbon content. It appears that once these three herbicides leach past the top 4 inches of these soils, retardation of the herbicides would be slight; they would be considered mobile herbicides. However, whether they would leach to ground water would be dependent on the rate of decomposition in the subsurface soils. Degradation potential of these subsurface soils needs to be determined.

Technical Abstract: The objective was to determine the sorption of hexazinone, sulfometuron methyl, and tebuthiuron to six acid, low base saturated sands from northeast Minnesota, northern Wisconsin, and Upper Michigan, and to correlate sorption to soil properties. Sorption K**d values for tebuthiuron on these soils ranged from 0.002 to 3.6 L kg-1 with greatest sorption on soils from the 0-5 cm depth and least on soils from depths greater than 65 cm. Sorption is correlated to OC content of the soil; mean K**oc equals 39 22 L kg-1. Sorption of hexazinone was substantially less than that of tebuthiuron on samples from different soils and depths. Hexazinone K**d values ranged from 0.0011 to 1.10 L kg-1. Sorption is correlated to soil OC; mean K**oc equals 19 L kg-1. Sorption of sulfometuron methyl to soils of 0-20 cm depths was lower than that of either hexazinone or tebuthiuron. Sorption K**d values 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, sorption did not correlate to OC content. It appears that factors affecting sorption change with soil depth. Sorption is correlated to OC for surface soils (0-20 cm depths), K**oc equals 5.4, and for subsurface soils (65-95 cm depths), K**oc equals 44 L kg-1. It appears that once these three herbicides leach past the top 10 cm of these soils, retardation of the herbicides would be slight; they would be considered mobile herbicides as evidenced by the low K**d values. However, whether they would leach to ground water would be dependent on the rate of decomposition in the subsurface soils.

Last Modified: 12/21/2014