Nitrogen Utilisation in Farming Systems: Optimisation to Minimise Losses

Keywords: N-surplus, manure use efficiency, nitrate leaching, nitrogen utilisation, upscaling, Danish agriculture, nitrogen policy.

Denmark is one of the world’s most intensively farmed countries and one of the largest exporters of animal products. This leads potentially to significant nitrogen (N) losses from agriculture, and policies to mitigate environmental effects of N have a high priority on the political agenda.

This paper presents the Danish measures to mitigate N-losses from agriculture, imposed since the early 1980s. These agro-environmental measures have shown remarkable results, investigated in the present paper, which focuses on the effects on N-losses and not the economic effects of this regulation. Accounting developments in N-losses on the national scale is difficult. Therefore, the development is described via three estimated, national level indicators: N-surplus (N-import minus N-export), N-efficiency (N-export per N-import), and N-leaching (simulated with the DAISY model and scaled up to the national level). N-surplus decreased from 490 kt N in 1985 to 313 kt N in 2002, and to 278 kt N in 2008. N-efficiency increased from 27% to 36% and 40% in the same period, while the N-leaching was estimated to be 334, 187 and 159 kt N, in 1985, 2002 and 2007 respectively. The trend in N leaching was confirmed by measurements in groundwaters of different age, and potential scenarios for further reductions in emissions of N and greenhouse gasses from Danish agriculture is presented.

In conclusion, N-leaching has been approximately halved since 1985, while crop yields have been maintained and animal production, expressed in kg N exported, increased by around 30% over the same period. The scenario studies show significant potentials for further reductions in N-losses, while maintaining production and increasing efficiency. However, the economic costs and benefits of the various types of nitrogen regulation is still an open question, which needs to be taken into account in a world with increased demands for agricultural products. The results presented may be an important input for such discussion.

Tommy Dalgaard, Nick Hutchings, Christen Børgesen, Finn Pilegaard Vinther, Aarhus University, Department of Agroecology, P O Box 50, 8830 Tjele, Denmark, and

Birgitte Hansen, Geological Survey of Denmark and Greenland (GEUS), Lyseng Allé 1, 8270 Højbjerg, Denmark.

24 pages, 11 figures, 5 tables, 34 references.