Abstract: The utilization, residue, loss and transport dynamics of nitrogen on orchard via soil in early spring by seven-year-old‘Gala’apple trees (Malus domestica) / Malus hupehensis were studied, using tracertechnique of ¹⁵N. The results showed that the utilization ratio of N fertilizer was low. At full-bloom stage, the utilization ratio of N fertilizer was lower (11.38% ). After fruit harvest, the utilization ratio of N fertilizer was the highest. At full-bloom stage, the residue rate of N fertilizer was the highest ( 57.10% ). After fruit harvest, the residue rate of N fertilizer was the lowest. The residue rates of different phenophase are different. At full-bloom stage, the residue rate of N fertilizer of 20 - 40 cm layer was the highest and, after fruit harvest,it was the lowest. At the new shoot growth stage, the residue rate of N fertilizer ( 0 - 20 cm layer) was the highest and, at fruitmaturity stage, it was the lowest. However, the residue rate of N fertilizer (40 - 60 cm layer) was up to the highest at fruit rap id-swelling stage. After fruit harvest, the residue rate of N fertilizer (0- 20 cm layer) was higher than that at fruit maturity stage and the residue rate of N fertilizer (other layers)was the lowest. On the contrary, the loss rate of N fertilizer was improved gradually with the process of phenophase. At full-bloom stage, itwas the lowest to 31.53% , and after harvest, the tip top was 58.40%.

Key words: apple, ¹⁵N, urea, utilization, residue, loss