Trifluralin Behavior in Soil. II. Volatilization as Influenced by Concentration, Time, Soil Moisture Content, and Placement¹

Vapor loss of trifluralin from water was found to be proportional to concentration, with losses being greater uring a 12‐hour period than during an 8‐hour period. Vapor losses were greater from a soil at maximum retentive capacity than from a soil at field capacity when the trifluralin was applied at equal rates to the soil surface. This is attributed to a greater proportion of free liquid available for vapor loss (high moisture), more trifluralin in the liquid due to the solubility effect, and to competition of water with the herbicide for adsorption sites. Placement of trifluralin 1.27 cm (½ inch) below the soil surface resulted in a very low vapor loss of the same magnitude for both moisture regimes. The experiments were run in a vapor‐trap apparatus involving still air. It is presumed that air movement would accelerate vapor losses of this compound under certain conditions.