To explore the effects of different fulvic acid application rates on 15N-urea absorption, utilization, residue amount, loss and fruit yield and quality, fifteen-year-old 'Red General'/ Malus micromalus Makino was selected as experiment material by using the 15N-labeled tracer technique. Five treatments were established: single urea (CK), combination of urea and fulvic acid with varied rates (NF1, NF2, NF3 and NF4 represented 75, 150, 300 and 450 kg·hm-2 fulvic acid application rates, respectively). The main results were as follows: the 15N derived from fertilizer (Ndff) in root, one-year-old branch and leaf were displayed with an order of NF3>NF4>NF2>NF1>CK at the fruit maturity stage, and significant difference was observed in Ndff value among the five treatments. The total N content and 15N absorption amount were highest in NF3, followed by NF4, and lowest in CK. Compared with CK, the 15N utilization rate in NF1, NF2, NF3 and NF4 was increased by 14.2%, 33.5%, 64.2% and 50.0%, and the 15N loss rate was decreased by 9.1%, 18.5%, 37.1% and 28.7% respectively. The residue amount of 15N-urea varied across different treatments, and that in 0-60 cm soil layer under combination of urea and fulvic acid was significantly higher than CK, with the highest value occurred in NF3, while it was lower than CK in 60-100 cm soil layer. In comparison with CK treatment, the largest increment of yield per plant and net income appeared in NF3, with an enhancement of 15.8% and 20.2%, respectively. In addition, the fruit hardness, soluble solid and sugar-acid ratio reached the highest value in NF3. Considering the responses of fruit yield and N utilization efficiency, the suitable fulvic acid application rate was 326.41-350.61 kg·hm-2.
以15年生红将军/八棱海棠为试材,运用15N同位素示踪技术,设置单施尿素(CK)及尿素配施不同用量黄腐酸处理(黄腐酸用量分别为75、150、300和450 kg·hm-2,分别以NF1、NF2、NF3和NF4表示),研究不同黄腐酸用量对苹果植株15N-尿素吸收、利用、残留、损失及果实产量和品质的影响.结果表明: 至果实成熟期,苹果根系、一年生枝和叶片的Ndff值(植株器官从肥料中吸收分配到的15N量对该器官全氮量的贡献率)均为NF3>NF4>NF2>NF1>CK,且各处理间差异显著.植株全氮量和15N吸收量均以NF3处理最大,其次为NF4处理,CK处理最低.与CK处理相比,NF1、NF2、NF3和NF4处理15N利用率分别提高了14.2%、33.5%、64.2%和50.0%,而15N损失率分别降低了9.1%、18.5%、37.1%和28.7%.不同处理土壤15N残留量不同.配施黄腐酸处理0～60 cm土层15N残留量显著高于CK处理,其中以NF3处理最多,而在60～100 cm土层显著低于CK处理.NF3处理单株产量和纯收益较CK处理增幅最大,分别为15.8%和20.2%,其次为NF4处理,同时,NF3处理果实硬度、可溶性固形物含量和糖酸比均达到最高水平.通过对果实产量和氮素利用率与黄腐酸施用量进行拟合分析,得出本试验条件下适宜的黄腐酸用量为326.41～350.61 kg·hm-2.
Keywords: 15 N-urea; apple; fate of 15 N; fulvic acid; yield.