|Bresnahan, Gail - ND STATE UNIVERSITY|
|Dexter, Alan - ND STATE UNIVERSITY|
|Lueschen, William - UNIVERSITY OF MINNESOTA|
Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 22, 1999
Publication Date: N/A
Technical Abstract: Soil pH affects imazethapyr sorption-desorption, which in turn can affect persistence and bioavailability. Long-term carryover has been observed in soil that is below pH 6.5, resulting in significant sugarbeet damage. We found imazethapyr concentration decreased rapidly in field soil regardless of pH. In spite of similar amounts of imazethapyr in aged soils, there were edifferences in bioavailability, which can be explained by sorption- desorption. At low pH more imazethapyr was sorbed than at high pH, but it readily desorbed. At high pH less imazethapyr was sorbed initially, but it did not readily desorb. Thus, after three months the remaning imazethapyr in low pH soil was readily desorbable and bioavailable, resulting in injury to canola and sugarbeet. Liming aged, low pH soil released bound imazethapyr residues, which were then degraded.