73 The Development of the EU-Rotate_N Model and Its Use to Test Strategies for Nitrogen Use across Europe C.R. Rahn 1 , K. Zhang 1 , R. Lillywhite 1 , C. Ramos 2 , J. Doltra 2 , J.M. de Paz 3 , H. Riley 4 , M. Fink 5 , C. Nendel 5,6 , K. Thorup-Kristensen 7 , A. Pedersen 7 , F. Piro 8 , A. Venezia 8 , C. Firth 9 , U. Schmutz 9 , F. Rayns 9 and K. Strohmeyer 10 1 Warwick HRI, University of Warwick, Wellesbourne, Warwick, CV35 9EF, United Kingdom 2 Instituto Valenciano de Investigaciones Agrarias (IVIA), Ctra. Moncada - Apdo. Oficial, 46113 Moncada, Spain 3 Consejo Superior de Investigaciones Científicas (CSIC), Apdo. Oficial, 46470 Albal/Valencia, Spain 4 Bioforsk, Apelsvoll Research Centre, 2350 Nes på Hedmark, Norway 5 Institut für Gemüse- und Zierpflanzenbau (IGZ), Theodor-Echtermeyer-Weg 1, 14979 Großbeeren, Germany 6 Present address: Leibniz-Centre for Agricultural Landscape Research, Institute for Landscape System Analysis, Eberswalder Straße 84, 15374 Müncheberg, Germany 7 Department of Horticulture, University of Aarhus, Research Centre Aarslev, Kirstinebjergvej 10, 5792 Aarslev, Denmark 8 Consiglio per la ricerca e la sperimentazione in agricoltura - Istituto sperimentale per l’orticoltura (CRA-ISOR), Via dei Cavalleggeri 25, Casella Postale 48, 84098 Pontecagnano, Italy 9 Henry Doubleday Research Association (HDRA), Ryton Organic Gardens, Coventry, CV8 3LG, United Kingdom 10 BOLAP GmbH, Obere Langgasse 40, 67346 Speyer, Germany Keywords: rotations, environment, leaching, decision support, fertiliser Abstract 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 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 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. INTRODUCTION Large amounts of nitrogen are applied to intensively cultivated land where field vegetables are grown. Demyttenaere et al. (1990) and Goulding (2000) showed that growing field vegetable crops can lead to large amounts of potentially leachable nitrate being left in the soil after harvest. Since the value of the produce is high in comparison to the cost of additional fertiliser the temptation to overfertilise is high, leading to greater risks of nitrate pollution. Increasing health and environmental concerns about high nitrate levels in produce and drinking water from such intensive land use now demands effective systems of fertiliser recommendation. Proc. 4 th IS on Ecol. Fert. Strat. Field Veg. Prod. Ed.: R.U. Larsen Acta Hort. 852, ISHS 2010