陇东旱区苹果园长期覆沙下氮素调控对树体生长发育和果实品质的影响机理

Sand covered is a main way of soil management in Longdong dry land apple orchards. Sand covered markedly improved fruit yield and quality. “Jingning Apple” is known for excellent qualities. Except for ascendant natural climate characteristics, Long-term sand covered remarkable improve the growth and development and fruit quality of Red Fuji apple. But, after the apple orchard of long-term sand covered that the soil environmental change characteristic and its influence on fruit tree growth and development, especially the quality formation mechanism is unclear. This project will choose the apple orchard of long-term sand covered and conventional cultivation model as comparison in dry land of eastern Gansu province. By set as different nitrogen levels, systematic research the trait of the soil physicochemical properties, nitrogen mineralization and the growth and development under long-term sand covered in dry land apple orchards.Ascertain its effects that the root domain soil environment and growth and development of apple trees. Analysis by synthesis the factors related to the influence of apple quality index. Ascertain the mechanisms of apple fine quality formation under sand covered. Make use of 15N-urea tracer technique, Studies on the property of absorption and partition and utilization of 15N-urea in the different part of the apple tree at different phenophase. Reveal the mechanisms of N management on the growth and development and fruit quality of Red Fuji apple under long-term sand covered in Longdong dryland regions. The research result can provide theoretical foundation of how to improve fruit yield and quality of Red Fuji apple.

覆沙是甘肃陇东地区旱地苹果园土壤管理的一种主要方式，能显著提高苹果产量和果实品质。甘肃陇东地区的“静宁苹果”以优质而著称，除优越的自然气候条件外，果园长期覆沙明显改善了树体生长发育和苹果品质。但长期覆沙对旱地苹果园土壤环境变化、果树生长发育和果实品质形成的作用机理尚不清楚，需要深入研究。本项目拟在甘肃陇东的静宁县选择长期覆沙苹果园，以清耕园为对照，通过设置不同氮素处理水平，研究长期覆沙下苹果园土壤理化性状、氮素矿化和树体生长发育特征，探明覆沙对苹果园根域土壤环境和树体生长发育的影响。综合分析覆沙下影响苹果品质指标的相关因素，探明覆沙苹果果实优良品质形成的机理。利用15N-尿素示踪技术，研究不同时期苹果根域土壤和树体主要器官氮素吸收、运转和分配规律，揭示旱区苹果园覆沙下氮素调控对树体生长发育和果实品质的影响机理。研究将为提高黄土高原旱区苹果产量和品质提供理论依据。

甘肃陇东地区的静宁苹果以优质而著称，除优越的自然气候条件外，具有甘肃特色的苹果园地面覆沙措施起到了重要作用，很大程度上改善了果园土壤理化特性。本研究对长期覆沙条件下不同氮素水平处理苹果氮素利用效率、土壤温湿度、养分、酶活性及果实品质进行了综合分析。主要结果如下，覆沙处理下施氮有利于生育后期地上部和总生物量累积，且施氮5g 15N-尿素处理于落叶前（10月）地下部生长极快。6月和8月份，覆沙条件下5g 15N-尿素处理多年生枝和细根Ndff值最高，分别为2.26%、3.21%和3.67%、5.89%。贮藏器官是树体最大的15N利用器官，其次为营养器官、生殖器官。植株15N利用率为3.38% ~ 38.00%，地面管理显著提高苹果幼树的15N利用率。综上，低施氮水平与地面管理既可促进幼树总生物量累积，又能提高氮素利用效率。苹果年生育周期里，覆沙处理0 ~ 80 cm土壤年平均温度比清耕园增高0.8℃，覆沙明显提高了休眠期含水量，全年比清耕处理高3.0 %，其中休眠期高5.0%。覆沙处理60 ~ 80 cm土壤全氮、0 ~ 20 cm土壤铵态氮和有效磷显著高于清耕，而0 ~ 20 cm土壤速效钾低于清耕。覆沙处理下0 ~ 20和> 20 ~ 40 cm土层中脲酶和磷酸酶活性在施氮330 kg/hm2水平下均达到最大值，而蔗糖酶活性则于施氮495 kg/hm2水平下最高；> 40 ~ 60 cm土层中过氧化氢酶活性随氮肥增施呈上升趋势。在330 ~ 495 kg/hm2施氮范围内，增施氮素能够显著提高果实横径、可溶性固形物、可滴定酸、维生素C及总糖含量，而过量施肥可显著增加果实产量。因此，330 ~ 495 kg/hm2为旱塬覆沙苹果园合理施氮范围。本研究明确了覆沙条件下苹果幼树对氮素吸收、运转和分配的特征，提出了适用于覆沙苹果园氮素施用标准，阐明覆沙与氮素对果实品质形成的影响，为提高甘肃陇东旱区苹果果实品质和保障果品质量安全提供理论支持。