Recovery of 15N-labeled nitrate injected into deep subsoil by maize in a Calcaric Cambisol in North China Plain

Recovery of 15N-labeled nitrate injected into 110cm soil horizon by maize in conditions of with or without N fertilizer application was studied using field micro-plot in a Calcaric Cambisol in North China Plain. The results showed that the recovery of 15N-labeled nitrate diffusing in 100-120cm after injection was 11.9% with N fertilizer application and 6.7% without N application in top soil layer respectively. N fertilizer applied to top soil layer stimulated growth of maize root in subsoil, thus increase the recovery of N-labeled nitrate injected into 110cm soil horizon at seedling stage. In relative drought experimental growth season, 15N-labeled nitrate didn't move downwards obviously because there was not free flow water passing through the 15N labeled horizon, it just diffused up or down about 20cm distance from labeled horizon. The results could be concluded that utilization of accumulated nitrate in deep subsoil by plants was acceptable to avoiding this kinds of nitrate leached to shallow ground water.