Leaching of Trifluralin, Benefin, and Nitralin in Soil Columns

Abstract

As determined by bioassay of segmented soil columns, a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), N-butyl-N-ethyl-a,a,a-trifluoro-2,6-dinitro-p-toluidine (benefin), and 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) varied in their leachability in a clay loam soil, even though their water solubility is the same. Nitralin was by far the more easily leached, benefin was least leached, and trifluralin slightly more so than benefin. Four A-in or more of water readily leached nitralin deep enough into the soil in amounts great enough to adversely affect the root growth of sensitive crop plants. Trifluralin and benefin were leached into the soil in relatively minute amounts, and these amounts were not great enough to affect root growth of sensitive crop plants when at least 0.5-in of untreated soil separated the seed from the layer of soil in which the herbicides had been mixed. The apparent breakdown product of nitralin present in moist soil was leached as readily as nitralin.