Fate of N-15 after one single application of labelled N fertilizer in thelong-term experiment Eternal Rye Cropping Halle [German]

摘要

To elucidate the fate of N in the long-term field experiment with continuous rye cropping in Halle, Germany (Haplic Phaeozem derived from sandy loess; mean annual precipitation: 466 mm) micro plots (9 m(2)) were established within the NPK main plot in 1993 and 1994 and the routine N dose (60 kg N ha(-1) a(-1)) was once applied as N-15 labelled fertilizer. In the subsequent four years each micro plot was analyzed for the N-15 withdrawn with grain and straw and that remaining in the soil after harvest. Parallel to this, micro plots on the unfertilized main plot received a single dose of 5 kg ha(-1) of high-label N-15 in order to achieve labelling of the annual N input from the air (similar to 40 kg ha(-1) a(-1)) and to follow its fate. - In the NPK treatment about one third of the labelled fertilizer N applied (= *N) was taken up by the rye in the first year, while nearly half of it remained in the soil (0-100 cm), and 10-15% was not recovered (most likely lost via leaching). During the following three years the amount of *N remaining in the soil decreased from 32.7 kg ha(-1) to 21.5 kg ha(-1). However, less than half of the remobilized *N had been taken up by the crop. On the unfertilized plot the uptake of *N was lower at the end of the experiment compared to the NPK plot, while the loss exceeded the comparative figure correspondingly.