Nitrogen leaching from grassland in Lithuania

Leaching losses from the soil contribute to undesired nutrients loads into surface water. It was the aim of the presented paper to give an overview of nitrogen (N) leaching losses from long-term drained cultivated grassland in relation to land use in Lithuania. In comparison with mown grassland (MG), the soil bulk density decreased between 2 and 9 % in set-aside grassland (SAG) within a 6-year period of investigation. Mineralization of the grass residues in spring increased the nitrate nitrogen (NO3-N) content 1.5 - 2.0-fold in the SAG compared with the MG treatment. Correspondingly, the NO3-N concentration in the drainage flow was 1.5 times higher. The mean annual NO3-N and total nitrogen (N-tot) leaching losses from the MG plots were 1.7 +/- 0.9 and 7.9 +/- 3.0 kg ha(-1) yr(-1), respectively. In comparison, the leaching losses from SAG that was not fertilized were 4.0 +/- 1.5 NO3-N kg ha(-1) yr(-1) and 11.6 +/- 3.2 kg N-tot ha(-1) yr(-1). Fertilization of MG with 60 kg N ha(-1) had no significant influence on the NO3-N content in the soil and drainage flow. Ploughing the grassland (PG) and sowing of spring cereals increased the NO3-N content in the soil by 15 to 40 mg kg(-1), but losses decreased after two years to values of 5 to 11 mg kg(-1). The NO3-N and N-tot concentration in the drainage flow increased by 3.5 - 6.1 and 6.2 - 9.1 mg L-1, respectively. Leaching losses were 12.4 kg NO3-N ha(-1) yr(-1) and 20.0 kg N-tot ha(-1) yr(-1). After two years, the leaching losses varied only slightly between 2.0 and 5.0 kg N-tot ha(-1) yr(-1).