Napropamide Adsorption, Desorption, and Movement in Soils

Abstract

Soil columns and soil thin-layer chromatography were used to evaluate the mobility of napropamide [2-(α-naphthoxy)-N,N,-diethylpropionamide] in various soils. The surface-applied herbicide did not move deeper than approximately 6 cm in a Teller sandy loam soil after a water application of 10.2 cm. The Rfvalues for napropamide and two reference herbicides were in the order of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] > napropamide > terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine]. The mobility of each herbicide was reduced with an increase in clay and organic matter content. Carbon-14 ring labeled napropamide was used to determine the adsorption and desorption characteristics of the herbicide in various soils. The Rfvalues obtained with napropamide and each soil agreed with the adsorptive characteristics. Small applications of a muck soil to a sand (2%, w/w) significantly increased herbicide adsorption and decreased herbicide desorption.