The scientific assessment on nitrogen flows in livestock farming: motives and methods

Abstract

Nitrogen is an essential nutrient in agriculture. Its reactive forms are the focus of concerns because they are responsible for a multitude of impacts on the environment and health. This was highlighted by the 2011 European Nitrogen Assessment, which drew up a critical inquiry on nitrogen imbalances due to livestock farming systems. The ambivalent status of nitrogen, both a resource for agriculture and a pollutant for environment, requires legal systems to find the equilibrium between the fertilising potential of the animal wastes and its possible negative effects on the environment. The European policies on nitrate and gaseous pollutants are the subject of much litigation with the European Commission. In this context, the French government asked for a synthesis of scientific knowledge on flows and fate of nitrogen related to livestock farms. Articles following in this review draw (i) the current situation, (ii) explain social and economic causes of the territorial variability of nitrogen pressure, (iii) quantify the flow on farms, (iv) look at indicators, (v) regulation instruments and finally (vi) identify options for reducing nitrogen pressure caused by livestock farming. In terms of materials and methods, a particular importance was given to peer recognition, and plurality inside the panel of experts and in the literature selection.