Beschreibung:
<jats:title>Abstract</jats:title>
<jats:p>In this study, 14 years of climate, stream flow, land management, nitrate-nitrogen (NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N) load and concentration data were analyzed to identify potential drivers for NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N losses at two tile-drained catchments under cropland use in northeastern Germany. Mean (±standard deviation) annual NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N concentrations were 9.7 ± 2.9 (drainage plot) and 6.8 ± 2.4 mg l<jats:sup>−1</jats:sup> (ditch catchment), while mean annual NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N loads amounted to 22 ± 16 and 20 ± 16 kg ha<jats:sup>−1</jats:sup>, respectively. Significant positive relationships between annual discharge and annual NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N losses underlined the importance of hydrologic conditions on NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N export mechanisms. No direct relationships were found between N soil surface surpluses and NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N losses. Any possible impact of N soil surface surpluses on NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N export rates was overridden by the hydro-meteorological conditions in the catchment. Positive correlations between the climatic water balance and NO<jats:sub>3</jats:sub>
<jats:sup>–</jats:sup>N losses suggest that agricultural catchments with similar characteristics as ours may face—without countermeasures—increased N losses in the future as regional climate projections predict wetter winters in the coming decades. Our analysis has further shown that effects of land management strategies aiming at reducing N losses into surface waters might only become visible with a delay of years or even decades.</jats:p>