An evaluation tool of the ratio between nitrogen-phosphorus rejects and the availability of land for french pig farms

The global aim of this study is to realise a territorial survey of nitrogen and phosphorus management in pig farms, taking into account nearby farms. Based on an analysis of existing environmental diagnosis techniques and spatial statistical analysis, a new method was developed, in order to :• take stock of the nitrogen and phosphorus structural situation in pig farms, in the midst of French farms;• test different hypothesis concerning environmental practices, agronomical potentialities of cultivated crops and possibilities of exporting excess manure to other farms.This work underlines the impact of two-phase feeding on the excesses of nitrogen and quantifies the nitrogen that has to be treated, according to environmental regulations in Structural Excess Zones (ZES) and vulnerable zones. Different scenarios can be the start of discussions on maximum inputs of organic fertilizer concerning the validity of the legal threshold of 170 kg of nitrogen per hectare per year in ZES and vulnerable zones or the impact of the creation of such thresholds for phosphorus in the years to come.An environmental analysis tool was developed during this study; its national scope, combined with the finest possible level of analysis, allows many hypotheses on technical choices or political decisions to be tested fairly accurately.It would be interesting to supplement this study by a regional approach, to be nearer of the realities of the farms, closely linked to their historical development.