The use of computer modelling to evaluate the agronomic, economic and environmental impacts of N management in contrasting organic rotations

Summary A new computer model (EU-ROTATE_N) has been developed with the aim of improving nitrogen management on all farms across Europe which include fi eld vegetables in their rotations. It brings together aspects of many existing models and contains a number of features to make it applicable to organic producers (e.g. taking account of nitrogen fi xation by legume containing leys, nitrogen conservation by winter cover crops and nitrogen supply by manures and composts). A key feature is the model’s ability to simulate economic output and this enables it to be of value to policy makers when considering the impact of new measures to reduce environmental pollution. This paper describes the model and some initial work that has been conducted to evaluate it under UK organic fi eld vegetable systems with contrasting fertility building strategies. Key words: Organic farming, fi eld vegetables, computer modelling, fertility building crops, rotational planning, farm economics Introduction EU-ROTATE-N is a new model that has been developed by a group of scientists in six Euro-pean counties. It considers the agronomic, environmental and economic implications of different management practices on rotations rather than on single crops. It is intended that it will be of use both for farmers/advisors (to help with rotation design) and policy makers (to assess the implications of possible legislation). The project began in 2003; although the new model was based on N-ABLE, an established soil and plant nitrogen model for fi eld vegetable rotations (Greenwood