Winter oilseed rape production is typically characterised by low nitrogen (N) use efficiency. Defining site-specific fertiliser strategies based on field trials and crop modelling may help to improve the ecologicalefficiency of this crop. However, no model has been evaluated for winter oilseed rape that simulates thegrowth of the plant as limited by the interaction of water and N. In this study, the APSIM canola modelwhich was originally developed for the temperate regions of Australia, was adapted for conditions inGermany and tested against measured data (total biomass, grain yield, leaf area index, N-uptake andsoil mineral N) at three sites near Göttingen (northern Germany). In the second part of the study, theevaluated model was used in a simulation experiment to explore site-specific climate and soil relatedproduction limitations to match fertiliser rates to yield targets. Historical weather data from four sitesacross northern Germany and a fertile loamy soil with different rooting depths, implicating different plantavailable water capacities, were used. Model results showed large differences in yield (up to 1000 kg ha−1)and N-balance (>30 kg ha−1) for 200 kg N-fertiliser rate ha−1between restricted (50 cm) and unrestrictedrooting depths. Simulated yields for such high N-fertiliser rate were lower for sites with continentalclimate than for sites close to the coast, reflecting different rainfall patterns. Results indicate that watersupply plays a critical role when maintaining high N use efficiency and reaching simultaneously grainyields of 4000 kg ha−1.