COMPARISON OF 2 TRANSPORT MODELS FOR PREDICTING NITRATES IN PERCOLATING WATER

The movement of nutrients and pesticides in soils is an important aspe ct of agriculture. Numerous models have been developed to predict the movement and transformations of such materials with varying degrees of complexity. The objective of this article is to present and compare t he performance of a specialized unsaturated zone transport model (TDNI T) in simulating nitrogen transport dynamics in soils against a widely accepted model (EPIC) as well as documented field studies in the stud y area. The model TDNIT is evaluated in simulating nitrogen transport and transformation and attendant hydrologic processes in a 13-year con tinuous corn cultivation series. Water percolation from the root zone, plant transpiration, soil evaporation, plant nitrogen uptake, and cro p yield from the two models compared favorably. The results of this st udy indicate that TDNIT performed well in predicting nitrate loadings below the root zone with TDNIT predicting a relatively reduced amount of total mineralization and denitrification. Even without calibration, TDNIT was found to be suitable for simulating nitrogen dynamics under the site conditions for which it was evaluated The relative simplicit y of TDNIT makes it a very suitable tool in simulating nitrogen transp ort through the unsaturated or vadose zones.