MODEL FOR PREDICTING SIMULTANEOUS MOVEMENT OF NITRATE AND WATER THROUGH A LOAMY SAND

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Abstract
A simulation model describing NO3- movement through a potato-cropped Plainfield loamy sand is described. Physical processes modeled include dispersion, convection, plant uptake, nitrification and mineralization. The soil water flow regime is treated approximately by dividing the soil profile into 3 layers between the surface and the water table and generating water flux and water content profiles by solving a series of mass balance, which included submodels for evapotranspiration and internal drainage. This information is combined with the solute equation and is solved numerically by the finite element method. Model predictions of NO3- movement often qualitatively agreed with field date when symmetrically comparable profiles were used. Nonuniform infiltration across the hill-furrow unit induced large local variability in solute transport. Predicted and measured NO3- concentrations in lysimeter leachates were in closer agreement when the nonuniform inflitration pattern was incorporated into the model.