Analytical modeling of nitrogen dynamics in soils and ground water

An analytical model, known as RISK-N, is developed to simulate nitrogen cyc ling in soils, and nitrate transport and fate in soils and ground water. Th e soil is separated into upper-root, lower-root, and intermediate-vadose zo nes, each with uniform properties. Transport in each soil zone is modeled o n the basis of complete mixing. Transport in the aquifer, however, is model ed using a two-dimensional advection-dispersion transport equation. A simul ation is made with a hypothetical corn plot, using meteorological, soil, hy drologic, and hydrogeological data for the South Platte River region of nor theastern Colorado. Sensitivity analyses an performed on model parameters. This study shows that the RISK-N model is capable of simulating nitrate lea ching rates, as well as ground-water concentrations, that are consistent wi th those obtained by numerical models, while requiring fewer input variable s.