Imazaquin movement in a field site that had Karnak silty clay soil was
evaluated during a 2-yr study to determine if leaching was a signific
ant dissipation mode for imazaquin. Imazaquin in water samples collect
ed from subsurface tile drainage was measured by immunoassay. Total im
azaquin losses due to leaching in 1993 were 0.8% of the total applied
and in 1994, practically zero. Imazaquin concentrations as high as 80
mu g L-1 were observed in drain water when rainfall occurred shortly a
fter herbicide application. Imazaquin concentrations were lower with e
ach successive drain flow event. Higher concentrations of imazaquin we
re associated with higher drainage flow, shortly after application. Ho
wever, 40 d after application, the levels of imazaquin were low (<7 mu
g L-1) even when high tile flow occurred. The time between applicatio
n and the first rainfall is an important factor in imazaquin leaching,
In the dry growing season of 1994, imazaquin concentration in drain w
ater did nor exceed 5 mu g L-1.