Developments in the nitrogen surplus and the fossil energy use in Danish agriculture during the 20th century

摘要

This paper goes through the development in nitrogen imports, nitrogen exports, nitrogen surplus, and fossil energy use in Danish agriculture during the 20th century. The nitrogen export in the form of animal and vegetable products rose throughout the century. Until around 1950, atmospheric N derived by leguminous crops was the dominant nitrogen import, but then N fertilisers became dominant. Since 1983, the fertiliser import and the nitrogen surplus have dropped, and nitrogen imported in the form of concentrate fodders now equals the amount imported in the form of fertilisers. The fossil energy use generally follows the fertiliser use and, like the nitrogen surplus, has been in a continuous decline since the mid-eighties after an almost exponential growth period from 1945-1970. On the basis of the nitrogen and energy accounts, the sustainability of the present development and the potential for future sustainable development are discussed. As a tool to structure this discussion, the development is divided into characteristic phases, where the lessons for each phase, regarding sustainable development, are derived and discussed according to the parallel historical developments during the 20th century.