Movement of Fluometuron Across and Through the Soil

Experiments were conducted to determine the effect of rainfall intensity, antecedent soil moisture, and time and subsequent rainfall on the runoff and leaching of soil‐applied fluometuron [1,1‐dimethyl‐3‐( a,a,a ‐trifluoro‐ m ‐tolyl)urea]. Fluometuron was applied to specially constructed field plots on a 1% slope and a simulated rainfall procedure was used to produce runoff. Runoff water and sediment, as well as vertical soil samples, were collected and analyzed for herbicide concentrations. The highest fluometuron concentrations were found on the sediment portion of the runoff, but the highest losses occurred in the liquid portion of the runoff. These losses were caused by the larger volume of water compared to sediment leaving the plot. The first 3.78 liters of runoff water leaving the plot contained a higher concentration of fluometuron than did a composite of the next 41.6 liters. Antecedent soil moisture had a greater effect on runoff losses than did rainfall intensity. Higher losses occurred when the herbicide was applied to a wet soil than to a dry soil. Fluometuron could not be detected in the runoff water collected 1 month after the first runoff‐producing water application. Total herbicide losses from each experiment were 1% or less of the total amount applied. Fluomeutron was leached to the 5‐ to 10‐cm soil depth with some treatments showing small quantities of herbicide in the 10‐ to 20‐cm layer.