The effect of wheat straw incorporation on imazaquin concentration and biological activity in soil solution was determined as a function of herbicide rate and time of incubation. Etowah silt loam, amended with wheat straw (2 g/kg) or unamended, received imazaquin (0, 31, 62, or 124 μg ai/kg oven-dry soil). Soils incubated at 25 C were subsampled 0, 12, 24, 48, and 96 h after treatment and soil solutions were analyzed for imazaquin, pH, and electrical conductivity. Wheat straw amendment, imazaquin rate, and time of incubation influenced the concentration of imazaquin in the soil solution. Imazaquin concentration in soil solution exhibited gradual linear declines with time. Relative length of sunflower radicles declined with increased imazaquin rate. Regression of relative radicle length on activity of imazaquin anion in soil solution indicated differential response in the presence of wheat straw-amended versus unamended soil.