Study on the fate of nitrogen fertilizer in winter wheat/summer maize rotation system in Beijing suburban

The fate of nitrogen fertilizer in current crop and succession crops in winter wheat and summer maize rotation system were studied using field 15N micro-plot. The results showed that crop yield would not increase when nitrogen application rate was above N 120kg /hm2. The recovery rate and residual rate of N 120 kg /hm2 were much higher than those of N 360 kg /hm2, but losses rate of N 120 kg /hm2 was much lower than that of N 360 kg /hm2. The residual rate in 0-100cm was 20.9%-48.4% after current crop harvest, the recovery rate of residual nitrogen fertilizer was less than 8%. There still had some residue nitrogen fertilizer after second or third crop harvest; the residual nitrogen fertilizer had much proportion of NO3--N with high application rate. Nitrogen leaching may play an important role in nitrogen losses.