Abstract: 【Objective】 The aim of the study is to provide a theoretical basis for N fertilizer rational application for ‘Fuji’ apple under field conditions. 【Method】 The absorption capacity and partitioning of 15N urea of major organs at different phenological stages were conducted using five-year-old field-cultivated ‘Fuji’ apple tree on M26 interstock treated with 15N -urea in early summer. 【Result】 The 15N -urea fertilizer was absorbed and transported by root firstly during the first month. The highest amount of 15N uptaken by root occurred at young fruit stage. The 15N absorption mainly contributed to new organs building with the development of plants in a month. The absorption capacity of 15N urea of new organs was higher in shoot, and then in leaf and fruit. The 15N absorption capacity and partitioning of roots was increased again at harvesting stage. The Ndff% of the major organs was higher in the next year than in the first year in fertilizer. At harvesting stage, the total N content and the amounts of 15N transportation to perennial stem were higher than those to new organs and roots. The 15N distribution ratio in new organs, perennial stem and roots were 23.5%, 40.4%, 36.1% in the first year and 27.7%, 34.9%, 37.4% in the second year, respectively. 【Conclusion】 The N fertilizer application in early summer mainly contented with the requirement to shoots development in the later season and was beneficial for accumulation of nutrition stored in apple trees. The N utilization efficiency of apple tree at fruit harvesting stage was 56.19% in the current year in this study.

Key words: apple, 15 N-urea, absorption, distribution, utilization