SIGNIFICANCE OF NITRATE LEACHING AND LONG TERM N IMMOBILIZATION AFTER DEEPENING THE PLOUGH LAYERS FOR THE N REGIME OF ARABLE SOILS IN NW GERMANY

摘要

Field studies were conducted to assess the turnover and the leaching of nitrogen in arable soils of Lower Saxony (NW Germany). The mean surplus N (difference between N inputs by fertilization and N export by the yield; 146 field plots) from 1985-1988 amounted to 38 kg ha(-1) yr(-1) in fine textured (clay, loam, silt) and to 98 kg ha(-1) yr(-1) in coarse (sandy) soils. Leaching of nitrate calculated by a simple functional model for simulation of the N regime over the winter period (i.e. mineralization and leaching) was 16 kg ha(-1) in the fine and 63 kg N ha(-1) in coarse soils (mean values of the winter periods 1985-1988 from 256 plots).