The main objective of the research is the modelling of the transport and fate of nitrogen in het unsaturated zone and the shallow groundwater system using different modelling approaches, varying from conceptual to physical based models, and to test which of the approaches is most suitable for the scale of analysis and the availability of data. The work involves the collection of field and regional data, the testing, calibration and validation of different modelling approaches, and the use of the models to identify at field and regional level the nitrogen fertilizer use that does not exceed the EC-norms for nitrate concentration in surface and groundwater.