Effect of nitrogen levels on absorption and utilization of nitrogen and yield of soybean

Frame experiment(pot without bottom) was conducted to investigate the influence of nitrogen levels on absorption and utilization of nitrogen and yield of soybean.Nitrogen fertilizer was(15NH4)2SO4,which was labeled with 15N.The results showed that the effect of N levels on N-accumulation and N-source of soybean was significant,and N-accumulation was various on different development stages.High N level facilitated the absorp-tion of fertilizer-N,inhibited nitrogen fixation by nodules,fertilizer-N accumulation followed the order:high N levelmid N levellow N level and reached the significant level(P0.01),nodulation-N accumulation followed the order:low N levelmid N levelhigh N level(P0.01).Yield of soybean was affected by N levels,yields of low-N level and mid-N level treatments did not reach the significantly different levels,but they were obviously higher than that of high-N treatment.