Prometryn Movement Across and Through the Soil

Abstract

Specially constructed runoff plots were used to study the effect of simulated rainfall intensity, antecedent soil moisture, and subsequent rainfall on prometryn [2,4-bis(isopropylamino)-6-methylthio-s-triazine] movement across and through a field soil with a 1% slope. The first cm (45.4 L) of runoff was collected and subdivided. The initial 3.8 L of runoff water generally contained a higher concentration of prometryn than did a composite from the next 41.6 L. The sediment contained a higher prometryn concentration than did the runoff water. However, due to the greater volume of water lost compared to sediment, over 90% of the prometryn lost was in the water fraction. When prometryn was applied to a dry soil and rainfall simulated, runoff losses of prometryn were 0.5% or less of the total amount initially applied. The first runoff producing simulated rainfall caused the largest prometryn losses, but prometryn could not be detected in the runoff 1 month subsequent to application. Prometryn was never detected at soil depths greater than 5 cm. Prometryn runoff was greater from plots in which the soil was wet at the time of application.