[Effects of different nitrogen application rates on 15N-urea absorption, utilization, loss and fruit yield and quality of dwarf apple].

Seven-year-old 'Yanfu3'/M26/M. hupehensis Rehd. seedlings and 15N trace technique were used to explore the characteristics of 15N-urea absorption, utilization, loss and fruit yield and quality under different nitrogen application rates (N100, N200 and N300). The main results were as follows: the plant growth, 15N absorption, utilization and loss differed significantly under different treatments. The plant leaf chlorophyll content (SPAD value), photosynthetic rate (Pn), total N content of leaves and the biomass, as well as the root-shoot ratio of N200 treatment were obviously higher than the N100 and N300 treatments. Significant differences were observed in the 15N derived from fertilizer (Ndff value) of different organs under different nitrogen application rates. The Ndff of fruits (flowers), leaves, one-year-old branch, and perennial branches in each measurement period was N100 >N200＞N300, while that of the roots at full-bloom and spring shoot growing slowly stage was N100 >N200＞N300, and in a trend of N200 >N100＞N300 at autumn shoot growing stage, fruit rapid-swel-ling stage and fruit maturity stage. At fruit maturity stage, plant 15N nitrogen utilization ratio of N200 treatment was 23.6%, which was obviously higher than the N100 (16.3%) and N300 (14.4%) treatments, with the 15N loss rate of 56.4%, obviously lower than the N100 (60.6%) and N300 (66.1%) treatments. There were significant differences among the treatments in fruit mass, yield per plant, soluble solid, fruit firmness, soluble sugar, titratable acids and sugar-acid ratio of different nitrogen rates, and the N200 treatment showed the best performance, followed by the N300 treatment, and then the N100 treatment.以7年生烟富3/M26/平邑甜茶为试材,采用15N同位素示踪技术,研究不同供氮水平[低氮(100 kg N·hm-2,N100)、中氮(200 kg N·hm-2,N200)和高氮(300 kg N·hm-2,N300)]对烟富3/M26/平邑甜茶15N-尿素吸收、利用、损失及产量和品质的影响.结果表明: 不同供氮水平植株的生长状况及氮素吸收、利用和损失特性差异显著.N200处理植株叶绿素含量(SPAD)、光合速率(Pn)、叶片全氮含量和生物量显著高于N100和N300处理,植株根冠比也显著增加.不同供氮水平下植株各器官对氮的吸收能力(Ndff值)存在显著差异,各测定时期果实(花)、叶片、一年生枝、多年生枝和中心干的Ndff值均为N100>N200＞N300;而根的Ndff值在盛花期和春梢缓长期为N100 >N200＞N300,在秋梢生长期、果实膨大期和果实成熟期为N200 >N100＞N300.在果实成熟期,N200处理15N肥料利用率为23.6%,显著高于N100(16.3%)和N300处理(14.4%),而15N损失率为56.4%,显著低于N100(60.6%)和N300处理(66.1%).不同供氮水平植株的平均单果质量、单株产量、可溶性固形物、硬度、可溶性糖、可滴定酸、糖酸比均存在显著差异,且均以N200处理最高,其次是N300处理,N100处理最低.