|Bresnahan, G - NORTH DAKOTA STATE UNIV|
|Dexter, A - NORTH DAKOTA STATE UNIV|
|Leuschen, W - UNIVERSITY OF MINNESOTA|
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: February 9, 1998
Publication Date: N/A
Technical Abstract: Previous research has indicated that imazethapyr will carryover for more than one year and carryover is greater in low than high pH soils. The objectives of this research were to determine imazethapyr adsorption- desorption in soils with naturally varying pH levels. Field studies were conducted to determine if increasing soil pH would decrease imazethapyr soil adsorption. Spent calcium carbonate, a byproduct of sugarbeet processing, was used at 6700 and 22,400 kg/ha, to increase soil pH. Imazethapyr at 0.036 kg/ha was applied on June 27, 1996 to soybean. Soil samples taken throughout the growing season were analyzed by HPLC. Greenhouse studies were conducted using imazethapyr-susceptible and resistant canola as the bioassay species. Results suggest that adsorption was greater at soil pH less than 6.0 compared to 7.5 or greater. The herbicide was bound more tightly at pH less than 6.0 compared to soil with pH greater than 6.0. The spent calcium carbonate had 14 percent less neutralization ability than virgin calcium carbonate. The soil pH was increased when spent lime was added. Severe sugarbeet injury was observed in both the low and high limed plots one year after imazethapyr was applied. Susceptible and resistant canola were greenhouse grown in soil from limed and unlimed field plots. Resistant canola was not injured by the imazethapyr. Susceptible canola was injured less by imazethapyr in limed than in unlimed soil. The interaction of pH, sorption-desorption, degradation, and carryover injury will be discussed.