A new model EU-ROTATE-N has been written which enables the assessment of the economic and environmental performance of nitrogen applied to crop rotations in either conventional or organic cropping for a wide range of crops and growing conditions in Europe. The model can simulate root development, the mineralization and release of N from soil organic matter and crop residues, the effect of freezing conditions, and water movement. New routines have also been added to estimate the effects of suboptimal rates of N and spacing on the marketable outputs and gross margins. Model performance was tested against experimental results and broadly simulated the patterns of crop growth, N response and N losses. The model provides a mechanism for comparing the relative effects of differing cropping and fertilisation practices on yield gross margin and losses of nitrogen through leaching. The running of a number of scenarios has demonstrated that nitrogen management in field vegetable rotations can be improved in Europe by following at least Good Agricultural Practice. The model also provides the potential for suggesting improvements which have a minimal effect on gross margin whilst reducing nitrogen losses.