Preferential Transport of Nitrate through Soil Columns Containing Root Channels

Abstract Preferential flow has been increasingly recognized as an important mechanism for water and solute transport. The objectives of this study were to characterize transport of NO 3 through root channels in uniformly packed soil columns and to compare three commonly used solute transport models in describing NO 3 transport through the soil‐root channel columns. Root channels were created by growing corn ( Zea mays L.) or alfalfa ( Medicago sativa L.) in 0.6‐m‐long soil columns. Transport of NO 3 was then systematically studied with each of these macropore systems at a range of fluxes (from 0.042 K sm to 0.47 K sm , where K sm is the saturated hydraulic conductivity of the macroporous system). A nonlinear least‐squares program was used to fit the convection‐dispersion equation (CDE), the physical nonequilibrium model (MIM) and a stochastic model (SM) to the experimental data. The results show that significant preferential movement of NO 3 occurred in the decayed root channels at fluxes as low as 0.042 K sm . The MIM model provided a better description of the breakthrough curves than the CDE and the SM, while none of them were adequate to predict the preferential movement of the solute.