EFFECTS OF WATER TABLE MANAGEMENT ON GROUNDWATER CONTAMINATION FROM THE USE OF PROMETRYN IN ORGANIC SOILS

In 1990, a two year study was undertaken to determine the effects of water table management on the movement of the herbicide prometryn in an organic soil in southern Quebec. Three water table management systems were used: controlled drainage, subsurface irrigation, and subsurface drainage. Results indicate that most of the prometryn movement through soil and into groundwater occurred during the first few months following application. In the subsurface drainage field, the concentrations of herbicide in groundwater were mostly higher than the drinking water quality standard of 10 μg/L. When subirrigation or controlled drainage was used, the concentration fell significantly below this level, indicating their usefulness in reducing the amount of prometryn reaching the groundwater. The study also demonstrated that, in an organic soil, pesticide movement was affected mainly by the water balance. The negative water balance during dry periods caused the soil water and pesticide to move upwards. This phenomenon wa...