ATRAZINE AND BROMIDE MOVEMENT THROUGH A SILT LOAM SOIL

The movement of agrochemicals through soil to groundwater is affected by soil properties, soil management, timing of leaching events, and kinetics of the transformation processes. This study was conducted to determine the pattern(s) of movement of Br and atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) through a field soil as affected by plow- and conservation-till corn (Zea mays L.), under severe leaching conditions. The soil surface inside double-ring infiltrometers was sprayed with chemicals, 1 wk later 10 cm of solution was applied under ponded flow conditions, and soil cores removed the next day for chemical analysis. The distribution patterns of Br and atrazine with soil depth were quite similar, with the largest proportion of the chemicals observed in the surface horizon, yet all cores showed some movement of chemicals to the deepest sampling depth (90 cm). However, on average <50% of the applied water, Br, and atrazine could be found. Two quite different processes seem to be involved in the movement of these chemicals through this soil: one-dimensional movement through the soil matrix and rapid downward movement through macropores - bypassing most of the soil matrix. These and other findings have major implications regarding the potential for contamination of groundwater by agro-chemicals.