There is a single result from the EU-Rotate_N project and that is the computer based decision support system - the EU-Rotate_N model. A new model has been written and tested which enables the assessment of the economic and environmental performance of crop rotations in either conventional or organic cropping for a wide range of crops and growing conditions in Europe. The model contains new routines to simulate root development, the mineralisation 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 sub-optimal 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 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 but the model also provides the potential for suggesting improvements which have a minimal effect on gross margin whilst reducing nitrogen losses.