Versuchsgut Lindhof - Versuchsgut für Ökologischen Landbau

Sources and characteristics of DON leaching from perennial grass-clover mixtures in Northern Europe

Efficient utilisation of nutrient in agricultural systems is essential in order to meet the constantly growing demand for sustainable production of food and to reduce environmental harmful losses. Grass-clover mixtures are a key crop at e.g. dairy farms supplying high quality fodder and at the same time building up soil fertility. The main input of nitrogen in such system is derived from nitrogen fixation of clover, which means that understanding the below ground dynamics is essential to reduce nitrogen loss and set up soil-plant models to simulate effects of different management strategies. The present knowledge does however not support this.

For many years leaching of nitrogen has only focussed on nitrate, but in recent years dissolved organic nitrogen (DON) has become of increasing interest as DON has been found to constitute up to 50 per cent of the total nitrogen lost. In order to assess the environmental fate of DON it is necessary to know the chemical and physical nature of DON being lost, as different forms of organic nitrogen will behave differently in soil matrix. The aim of this project was to investigate leaching, origin and characteristics of DON from grass-clover mixtures as influenced by management and climatic conditions, and to study N transfer dynamics between the mixture species. This was accomplished by conducting similar experiments in Iceland, Germany, and Denmark whit varying climatic, environmental, and soil properties. The project partners were:

  • Áslaug Helgadóttir, Faculty of Land and Animal Resources, Agricultural University ofIceland, Reykjavik, Iceland
  • Bodil Frankow-Lindberg, Dept. of Crop Production Ecology, Swedish University ofAgricultural Sciences, Uppsala, Sweden
  • Ralf Loges, Dept. of Crop Science and Plant Breeding, Christian-Albrechts-University,Kiel, Germany
  • Jørgen Eriksen, Dept. of Agroecology and Environment, Faculty of Agricultural Sciences,Aarhus University, Denmark


The project was funded by the Danish Research Council for Technology and Production Sciences.

Contact: Jim Rasmussen
Department of Agriculture and Environment
Faculty of Agricultural Sciences
Aarhus University
PO Box 50, 8830 Tjele
So far published:

  • Rasmussen, J. Gylfadóttir, T. Loges, R., Eriksen,J. and Helgadóttir, Á.: 2013: Spatial and temporal variation in N transfer in grass-white clover mixtures at three Northern European field sites. Soil Biology & Biochemistry 57, 654-662  DOI:10.1016/j.soilbio.2012.07.004