The fate of N-15-labelled urea in an alkaline calcareous soil under different N application rates and N splits

摘要

We aimed to quantitatively investigate the effects of rate and timing of nitrogen (N) application on fate of N-15-labelled urea in an alkaline calcareous soil during a winter wheat (WW) and summer maize (SM) seasons. The treatments consisted of conventional N application (i.e., WN300-2T or MN240-2T, 300 or 240 kg N ha(-1) with two N splits to WW or SM), reduced N application (i.e., WN210-2T or MN168-2T, 210 or 168 kg N ha(-1) with two N splits to WW or SM), recommended N application (i.e., WN210-3T or MN168-3T, 210 or 168 kg N ha(-1) with three N splits to WW or SM), and control (N0). The result showed that the fate of N-15 fertilizer was significantly influenced by rate and timing of the applied N. Compared with the conventional N treatment, crop N-15 recovery in the recommended N treatment increased significantly by 16.7 % for WW and 17.2 % for SM, but total N-15 losses reduced significantly by 12.3 and 13.5 %, respectively. Residual N-15 in 100-200 cm soil layer was the lowest in recommended N treatment, preventing leaching of much (NO3)-N-15 (-)-N to deeper soil layers. Our results indicated that the recommended N treatment at rate of 210 or 168 kg N ha(-1) with three N splits to WW or SM would maintain crop yields but significantly increase N recovery efficiency and reduce the risk of environmental pollution caused by N losses.