Napropamide Adsorption, Desorption, and Movement in Soils

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 R f values 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 R f values 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.