Tools to improve nitrogen (N) management for potatoes in the Pacific Northwest (PNW) are desirable in view of the concern on non-point source pollution of nitrate into groundwater in the Columbia Basin production region which is characterized by sandy soils and possible N inputs in excess of crop N requirement. A potato growth model was developed and integrated into the multi-year, multi-crop simulation mode CropSystVB to improve overall model capabilities for the assessment of N fate under different nitrogen and irrigation regimes in potato systems. In the integrated model, CropSystVB simulates the soil-water-plant-atmosphere system for a crop rotation, as well as the soil water and nitrogen budgets. When the crop in rotation is potato, the potato model simulates potato growth and development and plant carbon and N balances. A field experiment was conducted to obtain crop data required to parameterize the potato crop model under different levels of N and irrigation. Model simulations were compared to seasonally measured data of dry matter, leaf area index, plant N and yield of potatoes grown with 3 levels of applied N (168, 336, and 504 kg/ha) and 2 levels of applied water (100 and 75% ET). Results showed that the model simulated plant N and dry matter partition and yields adequately. Improved accuracy in the simulation of potato N and carbon balances by the integrated model demonstrates that this model can be used to predict soil and plant N dynamics and production of potato-based cropping systems.