基于15N示踪的库尔勒香梨园氮素去向研究

【目的】研究库尔勒香梨对15N肥料的利用、转移规律，探讨肥料在土壤和树体之间的氮素循环过程。【方法】采用15N同位素示踪技术，以6年生库尔勒香梨为供试材料，在新疆维吾尔自治区库尔勒市恰尔巴格乡下和什巴格村5队进行田间微区试验，每株均匀施入普通尿素N 667 g与 15N-尿素N 10 g，其中60%在果树萌芽前施用，剩余40%在膨果前期追施。分析库尔勒香梨从萌芽前期至果实成熟期氮素利用、土壤氮素残留及氮素气态损失特征。【结果】1) 随着生育时期推移，库尔勒香梨树体的生长中心不断变换，盛花期至新梢旺长期，树体的生长由根转换为叶和根两个中心；在果实膨大期和果实成熟期，则转化为根、果实和叶三个中心。库尔勒香梨氮肥利用率随生育期的推进而不断提高，在果实成熟期达到最大为18.5%。2) 0—120 cm土壤剖面中NO₃?-N和NH₄+-N残留量随着土层深度的增加逐渐减少，0—60 cm土层残留量显著高于60—120 cm土层。随着生育期推移，土壤剖面中NO₃?-N和NH₄+-N残留率不断减小，在果实成熟期残留率最低，分别为13.9%和8.41%，无机氮残留率为22.31%。3) 土壤氮素损失中，氨挥发和N₂O排放量仅为总损失量的4.19%，其中主要以氨挥发为主。【结论】氮肥回收率随生育期的推进 (除果实膨大期) 不断减小，于果实成熟期达到最小为41.0%；损失率与回收率趋势相反，在果实成熟期损失率高达59.0%。萌芽前期至果实成熟期氮肥去向表现为氮肥损失 > 土壤残留 > 树体吸收。

Fertilizer nitrogen fate in korla fragrant pear orchard using 15N tracing method

【Objectives】15N isotope tracer technology was used in this paper to study the use and transfer of fertilizer N in Korla fragrant pear trees and the fate of fertilizer N after applied into soil, to increase the understanding of the nitrogen cycle of fertilizer N in soil and tree body.【Methods】Six years’old Korla fragrant pear trees were used as the tested materials, a field mini-plot test was conducted in Team 5, Shibagh Village, Chabag Township of Korla City, Xinjiang Uygur Autonomous Region. Conventional urea N 667 g and 15N-urea N 10 g were applied in each pear tree, 60% of them being applied at the early budding stage and 40% at the early fruit expanding stage. The nitrogen utilization by pear trees, the soil nitrogen residual and nitrogen gas loss were analyzed from the early bud stage to the fruit harvest stage.【Results】1) With the growth stages advancing, the growth center of fragrant pear trees kept changing. Before blooming, the growth center accounted only in roots, and from the full-bloom to the new shoot growing stage, the centers were in both leaves and roots, and from the fruit expansion to fruit harvest stage they were in roots, fruits and leaves. With the development of pear trees, the utilization rate of fertilizer N was increased gradually with the advancing growing stager, with the maximum value of 18.5% at fruit harvest stage. 2) The residual amounts of NO₃–-N and NH₄+-N within the 0–120 cm soil profile decreased gradually, the deeper the less, and the residual amounts of NO₃–-N and NH₄+-N in the 0–60 cm soil layer were much higher than those in 60–120 cm soil layer. With the growth stage, the residual rates of NO₃–-N and NH₄+-N decreased in the soil profile, and the residual rate was the lowest at the fruit harvest stage with 13.9% and 8.41% respectively. The residual rate of inorganic nitrogen was 22.31%. 3) The total amount of ammonia volatilization and N₂O emission accounted only 4.19% for the soil nitrogen loss, and ammonia volatilization was the predominant way.【Conclusions】The recovery rate of fertilizer N decreased gradually with the growth stage advancing (except for fruit expanding), and the minimum value was 41.0% at the fruit harvest stage. The loss rate was opposite to the recovery rate, and the loss rate was as high as 59.0% at the fruit harvest stage. The fertilizer N fate was in the order of nitrogen loss>residue in soil>absorption by pear trees.