In mixed arable grassland systems there can be a considerable build-up of nitrogen (N) caused by input through symbiotic N2 fixation and by the deposition from grazing animals. After ploughing of such grazed grassland large amounts of inorganic N may be released through mineralisation and subsequently leached to deeper soil layers or eventually to the groundwater. However, not much is known about the contribution of dissolved organic nitrogen (DON) to the total amount of N leached
