ANALYSIS OF THE USE OF WATER AND NITROGEN IN EVOLVING FOOD PRODUCTION SYSTEMS. A COMPARISON AMONG THREE FRENCH CATTLE

Food production necessarily uses agricultural land and involves water consumption and nutrient mobilization. In the past food producing systems, livestock and crop production were tied together at a local land base for the livestock to receive feed inputs from agriculture and to supply crop production with nutrients through manure deposition. In the modern food production systems, feeds are often exchanged over long distances from primary production to livestock operations resulting in one way nutrient flows that accumulate locally and risk to enrich environments external to the agrosystems. In this study we conduct a parallel comparison of the water consumption, nitrogen circulation, land use and soil cover changes occurring on the nutritional acreage of the beef and dairy cattle among three French food producing systems of the 19th, 20th and 21st centuries. While the water expenses and land requirements per unit of final product have reduced in time, the animal acreage in the 21st system is clustered among regions and countries, the organic nitrogen loads increase up to 6-fold and the modification of the ration composition during this period involves a sharp withdrawal of the permanent vegetal land cover on the agricultural soil. Key words: cattle rations, crop water requirements, embedded water content, biological nitrogen fixation, nitrogen flow