STUDIES OF THE FLOW, SUPPLY AND LOSSES OF NITROGEN AND OTHER PLANT NUTRIENTS IN CONVENTIONAL AND ECOLOGICAL AGRICULTURAL SYSTEMS IN SWEDEN

Studies were made of plant nutrients, especially the flow, supply and losses of nitrogen in different agricultural and community systems in Sweden at the farm, regional and national levels. Nitrogen losses from the agricultural systems exceeded 100 kg/ha/year in southern Swedish regions. Losses exceeded 200 kg/ha/year in association with animal hus bandry. Nitrogen can be conserved by maximizing the recycling of crop nitrogen within the agroecosystem and between the agricultural and the community systems. This requires that the level of animal production on a given farm must be adjusted on the basis of the farm's crop-and f eed-production capacities which in turn are determined partly by the c limatic and soil conditions. Such an adjustment on mixed farm, regiona l and national levels, would contribute to minimize nitrogen and other plant nutrient losses to the environment. This would also decrease th e costs to the environment associated with artificial fertilizers.