晚秋叶施尿素提高矮化苹果翌春生长及果实品质的效果

【目的】研究晚秋叶施高浓度尿素对矮化苹果翌年春天氮素吸收、利用及成熟期果实品质的影响，以期为矮化果园合理施肥、提高氮肥利用率提供科学依据。【方法】以5年生烟富3/M26/平邑甜茶苹果为试材进行田间试验。试验设3个处理，每个处理5株树，单株为1次重复。用15N-尿素（丰度为10.22%）配成N 1.50%，3.00%和4.50%的水溶液，分别用毛笔涂抹苹果全树叶片的正反两面，每株树用量60 mL。以同样步骤，用普通尿素进行三个浓度的对照试验。于翌年盛花期（4月25日）进行局部取样，春梢生长期（6月15日）进行整株破坏性取样，测定个部位的含氮量和15N丰度，以及叶绿素含量及果实品质，计算肥料氮对该部位氮素吸收的贡献率。【结果】晚秋矮化苹果叶施不同浓度15N-尿素，叶片对叶面引入的氮素具有较高的吸收能力。不同叶施处理，植株翌年各器官的Ndff存在显著差异，且均以N 4.50%处理的最大，N 3.00%处理次之，N 1.50%处理最小，在盛花期，不同处理植株各器官均以多年生枝的Ndff值最高，其次是叶片，花和根，在春梢生长期，不同处理植株各器官均以叶片的Ndff值最高，其次是果实、一年生枝、多年生枝、根，中心干的Ndff值最小。在果实成熟期，不同处理苹果植株叶片的叶面积、叶绿素含量和叶片全氮含量均存在差异显著，且均以N 4.50%处理最高，其次N 3.00%和N 1.50%处理，对照处理最小；不同处理植株的平均单果重，单株产量、可溶性固形物、硬度、可溶性糖和糖酸比均存在差异显著，且均以N 4.50%处理最高，其次N 3.00%和N 1.50%处理，对照处理最小。【结论】晚秋对矮化苹果叶施不同浓度尿素，均显著增加了当年的贮藏营养，有利于翌年春天的营养生长和花芽分化，而且改善了叶片质量，不同程度的提高了苹果产量和果实品质。对于供试矮化苹果，适宜的喷施浓度是N 4.50%。

Foliage application of urea in late autumn will improve growth in the following spring and fruit quality of dwarfed apple

Objectives]In this paper, we studied the effects of urea foliar application in late autumn on the nitrogen absorption, utilization of apple trees in the following spring and the fruits quality at the fruit maturation period of dwarfed apple, hoping to provide scientific basis for appropriate fertilization on dwarfed apple orchards and improve the nitrogen efficiency.Methods] A field experiment was conducted uing five-year-old 'Fuji' 3/M26/M.hupehensis Rehd. seedlings as the experimental material. The seedlings were divided into three groups and each had 5 ones. The15N-urea (abundance 10.22%) was diluted into aqueous solution of N 1.50%, 3.00% and 4.50%, and 60 mL of the solutions were smeared onto both sides of the whole plant leaves. Common urea control of three N concentrations were made the same as the treatments. In the next year, the leaves, branches and roots samples were collected at the full-bloom stage (April 25th), and the whole plants were destructively sampled at the spring shoot growing stage (June 15th). The N contents and15N aboundance were determined, the chlorophyll contents and fruit quality were investigated, and the Ndff values were calculated.Results]There were significant differences in Ndff in different organs, and the highest one was in tretment of N 4.50%, followed by treatment N 3.00%, and the lowest in the N 1.50% treatment. At the full-bloom stage, the Ndff in perennial branches was the highest, then in leaves, flowers and roots in turn, indicating that the nitrogen absorbed by leaves was primarily stored in perennial branches. At the spring shoot growth stage, the Ndff in leaves was the highest, followed by annual branches, perennial branches, roots and stems in turn. The plant leaf area, SPAD and the total N contents of leaves were found significantly different amongst the treatments at the fruit maturity stage. The highest values was in N 4.50% treatment, then was in N 3.00% and 1.50% treatments, and the lowest value was in the control, which was consistent with the presentation of the physiological indicators, such as mean fruit weight, yield per plant, soluble solid, fruit firmness, soluble sugar content and sugar-acid ratio.Conclusions]Foliar application of urea on dwarfed apple trees in late autumn could improve the nutrient storage of the current year, enhance the vegetative growth and flower bud differentiation, improve the leaf area, and increase the yield and fruit quality of apples as a result. The appropriate foliar application concentration of urea is N 4.50% for the experimental apples cultivars.