| Abstract: | The objective was to estimate the potential risk of N leaching into the groundwater under various types of agriculture by using lysimeter experiments on the nitrogen(N)‐cycle of various soil types. Results were obtained with 12 weighable, monolithic lysimeters with a surface area of 1 m2, a total depth of 3 m, and free drainage. Mean annual N‐leaching losses of 5 to 44 kg ha—1 and nitrate concentrations of the seepage water (leachate) between 80 and 200 mg l—1 were measured during the period of intensive agricultural use. On fallow land with a well‐established grass vegetation, some nitrate was removed by the plants. As a result, the nitrate concentrations in the leachate were reduced significantly. Ecological farming measures generally reduced N leaching losses and kept the N‐concentration in the leachate below the German threshold value for drinking water with 50 mg l—1 nitrate. However, ploughing in of clover or leguminous vegetation and the application of farmyard manure in autumn caused the nitrate concentration in the leachate to rise significantly above the mentioned threshold value. |
