探讨减氮施肥措施对甘蔗各器官的氮素吸收与利用的影响，为甘蔗生产的合理施肥提供科学依据。设置3个施氮水平(低氮(N300):尿素300 kg·hm-2;中氮(N400):尿素400 kg·hm-2;高氮(N500，常规施氮量):尿素500 kg·hm-2)，采用田间微区15N示踪技术，分析减氮施肥对甘蔗田追肥后、苗期、伸长期和成熟期甘蔗叶、茎和根的氮素吸收与利用及土壤(0～10、10～20、20～40 cm)的氮肥残留率的影响。结果表明，伸长期和成熟期，减氮施肥没有显著影响甘蔗叶和茎15N累积量。追肥后、苗期、伸长期和成熟期，N500处理中甘蔗根氮素累积量、15N累积量、从肥料氮源吸收的氮量及从土壤氮源吸收的氮量普遍最高。苗期、伸长期和成熟期，N300处理中甘蔗叶、茎和根的氮素吸收量及肥料利用率均高于其他处理。伸长期，0～10、10～20、20～40 cm 土层的15N累积量在3个施氮处理中没有显著差异。追肥后、苗期、伸长期和成熟期，0～10、10～20、20～40 cm 土层中氮肥残留率普遍在N300处理中最高。综上，减氮施肥有利于提高甘蔗根的氮肥利用率，促进甘蔗茎的氮素利用率，进而影响甘蔗产量。
15N tracer analysis of nitrogen use efficiency in sugarcane organs under reduced nitrogen fertilization
Clarifying the influence of reduced nitrogen fertilization on nitrogen uptake and utilization of sugarcane organs can provide scientific basis for rational fertilization in sugarcane production.Based on 15N tracer technique,a micro-plot field experiment was conducted to investigate the effects of three application levels of nitrogen fertilizers[low level(N300):urea 300 kg·hm-2;middle level(N400):urea 400 kg·hm-2;high level(N500,the con-ventional nitrogen application):urea 500 kg·hm-2]on nitrogen uptake and utilization of leaves,stems and roots,and residual nitrogen rate of soil(0-10,10-20,20-40 cm)after topdressing and at stages of seedling,exten-sion,and mature,respectively.The results showed that reduced nitrogen fertilization did not affect the accumulation of 15N in leaves and stems at stages of extension and mature.Generally,accumulated N concentration,accumulated 15N concentration,amount of N derived from fertilizer and amount of N derived from soil of sugarcane root were higher in N500 treatment than that in the other treatments at stages of topdressing,seedling,extension,and ma-ture.At the stages of seedling,extension and mature,N uptake and fertilizer use efficiency of leaf,stem and root were higher in the N300 treatment than that in the other treatments.There were no significant differences of accu-mulated 15N concentration of soil at 0-10,10-20,20-40 cm layers among the three N treatments at extension stage.The N residual rate of 0-10,10-20,20-40 cm soil was higher in the N300 treatment than that in the other treatments at stages of topdressing,seedling,extension and mature.Collectively,reduced nitrogen fertilization is beneficial to improving fertilizer use efficiency of roots and stems,and consequently the yield of sugarcane.
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