Effects of two contrasting agricultural land‐use practices on nitrogen leaching in a sandy soil of Middle Germany

The objective of this study is to evaluate different agricultural land‐use practices in terms of N leaching and to give recommendations for a sustainable agriculture on sandy soils in Middle Germany. Soil mineral N (N min ) and leachate N were quantified at a sandy soil in N Saxony during 3 years. Two treatments were applied: intensive (I)—using inorganic and organic fertilizer and pesticides, and organic (O)—exclusively using organic fertilizer, legume‐based crop rotation, and no pesticides. Split application of mineral fertilizers did not result in substantial N losses at treatment I. Legumes induced a considerable increase of soil mineral N and particularly of leachate mineral N (N min_perc ) at treatment O. High N min_perc concentrations (up to 78 mg N L –1 ) were observed during as well as after the cultivation of legumes. These high N min_perc concentrations are the reason why clearly higher N min_perc losses were determined at treatment O (62 kg N ha –1 y –1 ) compared to treatment I (23 kg N ha –1 y –1 ). At both treatments, the quantity of N losses was strongly affected by the precipitation rates. Concentrations and losses of dissolved organic N (DON perc ) were assessed as above average at both treatments. The results suggest that the DON perc concentration is influenced by precipitation, soil coverage, and organic fertilizers. Higher values were determined in the percolation water of treatment O. The average annual DON perc losses amounted to 15 kg N ha –1 at I and to 32 kg N ha –1 at O. The average monthly percentage of DON perc losses on the loss of the dissolved total N of percolation water (DTN perc ) ranged between <1% and 55% at O and between 2% and 56% at I. For the whole measuring period of 29 months, the relative amounts of DON perc of DTN perc (21% at O and 25% at I) were more or less the same for both treatments. The results show that DON perc can contribute significantly to the total N loss, confirming the importance to consider this N fraction in N‐leaching studies. It was concluded that at sandy sites, a split application of mineral fertilizers, as applied at treatment I, seems to be more expedient for limiting the N leaching losses than legume‐based crop rotations.