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Increasing concentrations of nitrate-nitrogen (NO3-- N) in surface and groundwater resources are a major water quality concern. A five year experiment to examine NO3-- N leaching losses to subsurface drains under continuous maize (Zea mays L.) was carried out, where mineral N and two separate liquid dairy manure applications under different conditions were applied following current agronomic N management guidelines. Yearly cumulative drainage and mass of NO3-- N leached varied from 118 mm 353 mm, and 10.9 30.9 kg ha-1, respectively, over the five years. The timing and extent of N losses were associated with antecedent soil moisture conditions, soil temperature, preferential flow, precipitation, tillage and timing/rate/method of manure application. Well-calibrated dynamic simulation models can be used to integrate these factors, and predict the impact of different manure N management practices for maize production on N losses. We have developed such a model, the Precision Nitrogen Management (PNM) model, composed of LEACHN, the N module of LEACHM linked to a maize N uptake, growth and yield model. We compared PNM model predictions of daily drainage, mass of NO3-- N leached and NO3-- N concentration exiting the root zone with measured values in subsurface drains over the course of the study. The model predictions provided a good fit to the observed data. The adjusted R2 were 0.82 and 0.80, and the Wilmotts index of agreement was 0.93 and 0.94, respectively, for drainage and mass of NO3-- N leached.