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Environmental evaluation of dairy farms by dynamic modelling of farm activities and nutrient flows: Development and application of the simulator MELODIE

Xavier Chardon
Abstract : World consumption of animal products is increasing, but environmental impacts of animal farming are criticised. Research is necessary to help design efficient and environmentally friendly production systems. In this context, the modelling project MELODIE consists of dynamically simulating nutrient flows in dairy farms over the long term by integrating the decision-making processes of farmers. Predicted emissions of potentially harmful nutrients are used to perform ex-ante and multi-criteria evaluations of pressures exerted on the environment, in relation with climate variability. During this thesis project, the first version of the simulator was built, starting with a generic and expandable object-oriented analysis. This version, which integrates the system management and carbon and nitrogen flows, is expandable and further developments (e.g., economy, labour) are considered. The model is composed of a biotechnical system and a management system interacting with each other. The biotechnical system includes a set of pre-existing sub-models connected to simulate nutrient flows in the farm and the emissions of potentially harmful nutrients. The management system, the main innovation of MELODIE, simulates decisions at two time scales and provides resilience against climate variability. Each simulated year, a plan is devised depending upon the state of the system. This plan is then executed in a flexible manner, and altered if necessary, with a set of decisions taken at a daily time step. An application of the model is shown, comparing different ways of feeding cattle for a given farm configuration. The results show that the link between nitrogen farm-gate balance and nitrate leaching is valid over the long term, although year-to-year variability is high and makes interpreting nitrogen balances difficult over shorter periods.
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Submitted on : Monday, June 22, 2009 - 8:00:00 AM
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Xavier Chardon. Environmental evaluation of dairy farms by dynamic modelling of farm activities and nutrient flows: Development and application of the simulator MELODIE. Sciences of the Universe [physics]. AgroParisTech, 2008. English. ⟨NNT : 2008AGPT0058⟩. ⟨pastel-00004548⟩

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