不同水平位置施肥对‘嘎啦’苹果15N吸收、分配与利用的影响

Effect of different horizontal fertilizer placements on the characteristics of absorption,distribution and utilization of ^(15)N by Gala/Malus Hupehensi

【目的】氮素用量高,利用效率低是制约我国苹果产业可持续发展的重要因素。生产上,施肥位置不明确是造成肥料利用率低的主要原因之一。本文通过研究不同水平位置施肥嘎啦苹果对15N-尿素的吸收、分配与利用特性,确定科学合理的施肥位置,以达到提高肥料利用效率的目的。【方法】以15年生嘎啦苹果/平邑甜茶为试材,采用15N示踪技术,根据施肥部位在树冠投影中的分布情况设置内层(1/3投影)、中层(2/3投影)、外层(投影边缘以内约20 cm处)3个不同水平位置施肥处理。施肥方法为挖环状沟施肥,施肥深度约25 cm。在苹果的几个关键物候期(新梢旺长期、果实膨大期、果实成熟期)分器官采集样品,试验结束时整株解析采样。【结果】不同水平位置施肥处理果树在新梢旺长期和果实膨大期根部吸收的15N优先向新生营养器官运转;果实成熟期均以果实中Ndff值最高;不同处理间,各生育期同一器官的Ndff值存在差异,内层施肥处理显著高于外层和中层施肥处理,其中以根系和果实最为显著;随着物候期的推移,不同处理根系的Ndff值变化趋势不同,中层施肥和外层施肥处理根系的Ndff值均呈先下降后上升的趋势,而内层施肥处理根系的Ndff值在果实膨大期就已经达到最大值,并且从果实膨大期到果实成熟期一直维持在较高水平;3个处理中果实的Ndff值随物候期的推移均呈上升趋势,并在果实成熟期达到最大,此时中层施肥处理和内层施肥处理果实的Ndff值分别是外层施肥处理的1.43和1.42倍;在新梢旺长期和果实膨大期果实的Ndff值从到大小依次为内层>外层>中层。不同物候期各器官的15N分配率存在显著差异,但不同水平位置施肥处理之间的差异并不显著;到果实成熟期3个处理的氮肥分配率均表现为贮藏器官>营养器官>生殖器官。果实成熟期,植株的15N利用率以内层施肥处理最高,为29.25%;中层施肥处理次之,为19.33%;外层施肥处理最低,为19.04%。内层施肥处理的氮肥利用率分别为外层和中层施肥处理的1.51和1.54倍。【结论】内层施肥处理植株各器官对肥料的吸收征调能力均显著高于中层和外层施肥处理,其中以细根最为显著;不同水平位置施肥对15N在各器官中的分配率影响不大;内层施肥处理15N利用率显著高于中层和外层施肥处理。

[ Objectives ] High nitrogen dosage and low use efficiency become one of important reasons of restricting sustainable development of apple industry in China. Unclear fertilizer placement is one of the main reasons of low fertilizer utilization rate in the production. Therefore, an experiment was carried out to figure out reasonable fertilizer placement, improve fertilizer utilization ratio and reduce waste by studying differences of different level fertilization effect. [ Methods] The experiment was carried out to study the effects of different fertilizer placements on the characteristics of notrogen absorption, distribution and utilization of fifteen year old apple trees （ Gala/Malus hupehensis） using 15N urea tracer technique. According to the scope of canopy projection, we set three different fertilizer placements, including 1/3 of canopy projection, referred to as inner fertilizer treatment （ I ）, 2/3 of canopy projection （middle fertilizer treatment, M） and about 20 cm inside to the edge of canopy projection （outer fertilizer treatment, O）. The fertilizing method was digging circular furrows on the three placements we had set and backfilling soil after the fertilization. The depth of the furrows was about 25 cm. Samples at the key phonological phases of apple trees were collected and separated at the end of the experiment. [ Results ] The absorbed 15N by roots transfers to new vegetative organs prior at the new shoot growing stage and fruit rapid-swelling stage under the different horizontal fertilization placements. The Ndff values of fruits are the highest among the organs at the fruit maturity stage under the three fertilization treatments. The Ndff values of the same organ are different under different fertilization treatments, and the Ndff values of the organs under the inner treatment are significant higher than those under the outer and middle fertilization treatments, especially for roots and fruits. The roots under the three treatments show different variation tendency as the phonological phase changing Ndff values of , and these of the inner fertilization are greater than those of the other treatments. The Ndff values of roots under the M and O treatments present a trend of upward after a fall first. But in the treatment I, the Ndff value of root is increasing until reaches the highest level at the fruit maturity stage. The Ndff values of fruits under the three treatments all present an increasing tendency as the phonological phase changing and reach the maxima at the fruit maturity stage, and the Ndff values of fruits in M and I are respectively 1.43 and 1.42 times of that under the treatment O. The result of the Ndff values of fruit at the new shoot growing stage and fruit rapid-swelling stage is I 〉 O 〉 M. The 15N distributions in the organs at different phonological phases are significantly different and are not significantly different among different treatments. At the fruit maturity stage, the trend of the nitrogen distribution in different organs under different fertilization treatments is consistent, storage organs 〉 vegetative organs 〉 reproductive organs, and the values of NUE under different treatments are I 〉 M 〉 O. The NUE of trees under the I treatment is 29.25%, which is significantly higher than those under the other two treatments （19.33% and 19.04% ）. [ Conclusions] Fertilization placement significantly affects plant organs＇ ability of absorbing fertilizer, especially roots. Different fertilizer placements show little effects on the nitrogen allocation rate but obviously affect the nitrogen utilization efficiency. Combining previous research results and the results of this experiment, it suggests that for ridging planted orchard, fertilizing at 1/3 of the canopy projection could improve the utilization rate of nitrogen fertilizer.